Commit Graph

411 Commits

Author SHA1 Message Date
Peter Hilber
14274d0bd3 timekeeping: Fix cross-timestamp interpolation for non-x86
So far, get_device_system_crosststamp() unconditionally passes
system_counterval.cycles to timekeeping_cycles_to_ns(). But when
interpolating system time (do_interp == true), system_counterval.cycles is
before tkr_mono.cycle_last, contrary to the timekeeping_cycles_to_ns()
expectations.

On x86, CONFIG_CLOCKSOURCE_VALIDATE_LAST_CYCLE will mitigate on
interpolating, setting delta to 0. With delta == 0, xtstamp->sys_monoraw
and xtstamp->sys_realtime are then set to the last update time, as
implicitly expected by adjust_historical_crosststamp(). On other
architectures, the resulting nonsense xtstamp->sys_monoraw and
xtstamp->sys_realtime corrupt the xtstamp (ts) adjustment in
adjust_historical_crosststamp().

Fix this by deriving xtstamp->sys_monoraw and xtstamp->sys_realtime from
the last update time when interpolating, by using the local variable
"cycles". The local variable already has the right value when
interpolating, unlike system_counterval.cycles.

Fixes: 2c756feb18 ("time: Add history to cross timestamp interface supporting slower devices")
Signed-off-by: Peter Hilber <peter.hilber@opensynergy.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: John Stultz <jstultz@google.com>
Link: https://lore.kernel.org/r/20231218073849.35294-4-peter.hilber@opensynergy.com
2024-02-19 12:18:51 +01:00
Peter Hilber
87a4113088 timekeeping: Fix cross-timestamp interpolation corner case decision
The cycle_between() helper checks if parameter test is in the open interval
(before, after). Colloquially speaking, this also applies to the counter
wrap-around special case before > after. get_device_system_crosststamp()
currently uses cycle_between() at the first call site to decide whether to
interpolate for older counter readings.

get_device_system_crosststamp() has the following problem with
cycle_between() testing against an open interval: Assume that, by chance,
cycles == tk->tkr_mono.cycle_last (in the following, "cycle_last" for
brevity). Then, cycle_between() at the first call site, with effective
argument values cycle_between(cycle_last, cycles, now), returns false,
enabling interpolation. During interpolation,
get_device_system_crosststamp() will then call cycle_between() at the
second call site (if a history_begin was supplied). The effective argument
values are cycle_between(history_begin->cycles, cycles, cycles), since
system_counterval.cycles == interval_start == cycles, per the assumption.
Due to the test against the open interval, cycle_between() returns false
again. This causes get_device_system_crosststamp() to return -EINVAL.

This failure should be avoided, since get_device_system_crosststamp() works
both when cycles follows cycle_last (no interpolation), and when cycles
precedes cycle_last (interpolation). For the case cycles == cycle_last,
interpolation is actually unneeded.

Fix this by changing cycle_between() into timestamp_in_interval(), which
now checks against the closed interval, rather than the open interval.

This changes the get_device_system_crosststamp() behavior for three corner
cases:

1. Bypass interpolation in the case cycles == tk->tkr_mono.cycle_last,
   fixing the problem described above.

2. At the first timestamp_in_interval() call site, cycles == now no longer
   causes failure.

3. At the second timestamp_in_interval() call site, history_begin->cycles
   == system_counterval.cycles no longer causes failure.
   adjust_historical_crosststamp() also works for this corner case,
   where partial_history_cycles == total_history_cycles.

These behavioral changes should not cause any problems.

Fixes: 2c756feb18 ("time: Add history to cross timestamp interface supporting slower devices")
Signed-off-by: Peter Hilber <peter.hilber@opensynergy.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/20231218073849.35294-3-peter.hilber@opensynergy.com
2024-02-19 12:18:51 +01:00
Peter Hilber
84dccadd3e timekeeping: Fix cross-timestamp interpolation on counter wrap
cycle_between() decides whether get_device_system_crosststamp() will
interpolate for older counter readings.

cycle_between() yields wrong results for a counter wrap-around where after
< before < test, and for the case after < test < before.

Fix the comparison logic.

Fixes: 2c756feb18 ("time: Add history to cross timestamp interface supporting slower devices")
Signed-off-by: Peter Hilber <peter.hilber@opensynergy.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: John Stultz <jstultz@google.com>
Link: https://lore.kernel.org/r/20231218073849.35294-2-peter.hilber@opensynergy.com
2024-02-19 12:18:51 +01:00
Peter Zijlstra
d16317de9b seqlock/latch: Provide raw_read_seqcount_latch_retry()
The read side of seqcount_latch consists of:

  do {
    seq = raw_read_seqcount_latch(&latch->seq);
    ...
  } while (read_seqcount_latch_retry(&latch->seq, seq));

which is asymmetric in the raw_ department, and sure enough,
read_seqcount_latch_retry() includes (explicit) instrumentation where
raw_read_seqcount_latch() does not.

This inconsistency becomes a problem when trying to use it from
noinstr code. As such, fix it by renaming and re-implementing
raw_read_seqcount_latch_retry() without the instrumentation.

Specifically the instrumentation in question is kcsan_atomic_next(0)
in do___read_seqcount_retry(). Loosing this annotation is not a
problem because raw_read_seqcount_latch() does not pass through
kcsan_atomic_next(KCSAN_SEQLOCK_REGION_MAX).

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Tested-by: Michael Kelley <mikelley@microsoft.com>  # Hyper-V
Link: https://lore.kernel.org/r/20230519102715.233598176@infradead.org
2023-06-05 21:11:03 +02:00
Geert Uytterhoeven
158009f1b4 timekeeping: Fix references to nonexistent ktime_get_fast_ns()
There was never a function named ktime_get_fast_ns().
Presumably these should refer to ktime_get_mono_fast_ns() instead.

Fixes: c1ce406e80 ("timekeeping: Fix up function documentation for the NMI safe accessors")
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: John Stultz <jstultz@google.com>
Link: https://lore.kernel.org/r/06df7b3cbd94f016403bbf6cd2b38e4368e7468f.1682516546.git.geert+renesas@glider.be
2023-04-26 23:43:16 +02:00
Randy Dunlap
f3cb80804b time: Fix various kernel-doc problems
Clean up kernel-doc complaints about function names and non-kernel-doc
comments in kernel/time/. Fixes these warnings:

  kernel/time/time.c:479: warning: expecting prototype for set_normalized_timespec(). Prototype was for set_normalized_timespec64() instead
  kernel/time/time.c:553: warning: expecting prototype for msecs_to_jiffies(). Prototype was for __msecs_to_jiffies() instead

  kernel/time/timekeeping.c:1595: warning: contents before sections
  kernel/time/timekeeping.c:1705: warning: This comment starts with '/**', but isn't a kernel-doc comment.
   * We have three kinds of time sources to use for sleep time
  kernel/time/timekeeping.c:1726: warning: This comment starts with '/**', but isn't a kernel-doc comment.
   * 1) can be determined whether to use or not only when doing

  kernel/time/tick-oneshot.c:21: warning: missing initial short description on line:
   * tick_program_event
  kernel/time/tick-oneshot.c:107: warning: expecting prototype for tick_check_oneshot_mode(). Prototype was for tick_oneshot_mode_active() instead

Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/20230103032849.12723-1-rdunlap@infradead.org
2023-01-03 11:07:58 +01:00
Jason A. Donenfeld
b8ac29b401 timekeeping: contribute wall clock to rng on time change
The rng's random_init() function contributes the real time to the rng at
boot time, so that events can at least start in relation to something
particular in the real world. But this clock might not yet be set that
point in boot, so nothing is contributed. In addition, the relation
between minor clock changes from, say, NTP, and the cycle counter is
potentially useful entropic data.

This commit addresses this by mixing in a time stamp on calls to
settimeofday and adjtimex. No entropy is credited in doing so, so it
doesn't make initialization faster, but it is still useful input to
have.

Fixes: 1da177e4c3 ("Linux-2.6.12-rc2")
Cc: stable@vger.kernel.org
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
2022-07-18 15:04:04 +02:00
Linus Torvalds
ac2ab99072 Random number generator updates for Linux 5.19-rc1.
-----BEGIN PGP SIGNATURE-----
 
 iQIzBAABCAAdFiEEq5lC5tSkz8NBJiCnSfxwEqXeA64FAmKKpM8ACgkQSfxwEqXe
 A6726w/+OJimGd4arvpSmdn+vxepSyDLgKfwM0x5zprRVd16xg8CjJr4eMonTesq
 YvtJRqpetb53MB+sMhutlvQqQzrjtf2MBkgPwF4I2gUrk7vLD45Q+AGdGhi/rUwz
 wHGA7xg1FHLHia2M/9idSqi8QlZmUP4u4l5ZnMyTUHiwvRD6XOrWKfqvUSawNzyh
 hCWlTUxDrjizsW5YpsJX/MkRadSC8loJEk5ByZebow6nRPfurJvqfrcOMgHyNrbY
 pOZ/CGPxcetMqotL2TuuJt5wKmenqYhIWGAp3YM2SWWgU2ueBZekW8AYeMfgUcvh
 LWV93RpSuAnE5wsdjIULvjFnEDJBf8ihfMnMrd9G5QjQu44tuKWfY2MghLSpYzaR
 V6UFbRmhrqhqiStHQXOvk1oqxtpbHlc9zzJLmvPmDJcbvzXQ9Opk5GVXAmdtnHnj
 M/ty3wGWxucY6mHqT8MkCShSSslbgEtc1pEIWHdrUgnaiSVoCVBEO+9LqLbjvOTm
 XA/6YtoiCE5FasK51pir1zVb2GORQn0v8HnuAOsusD/iPAlRQ/G5jZkaXbwRQI6j
 atYL1svqvSKn5POnzqAlMUXfMUr19K5xqJdp7i6qmlO1Vq6Z+tWbCQgD1JV+Wjkb
 CMyvXomFCFu4aYKGRE2SBRnWLRghG3kYHqEQ15yTPMQerxbUDNg=
 =SUr3
 -----END PGP SIGNATURE-----

Merge tag 'random-5.19-rc1-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/crng/random

Pull random number generator updates from Jason Donenfeld:
 "These updates continue to refine the work began in 5.17 and 5.18 of
  modernizing the RNG's crypto and streamlining and documenting its
  code.

  New for 5.19, the updates aim to improve entropy collection methods
  and make some initial decisions regarding the "premature next" problem
  and our threat model. The cloc utility now reports that random.c is
  931 lines of code and 466 lines of comments, not that basic metrics
  like that mean all that much, but at the very least it tells you that
  this is very much a manageable driver now.

  Here's a summary of the various updates:

   - The random_get_entropy() function now always returns something at
     least minimally useful. This is the primary entropy source in most
     collectors, which in the best case expands to something like RDTSC,
     but prior to this change, in the worst case it would just return 0,
     contributing nothing. For 5.19, additional architectures are wired
     up, and architectures that are entirely missing a cycle counter now
     have a generic fallback path, which uses the highest resolution
     clock available from the timekeeping subsystem.

     Some of those clocks can actually be quite good, despite the CPU
     not having a cycle counter of its own, and going off-core for a
     stamp is generally thought to increase jitter, something positive
     from the perspective of entropy gathering. Done very early on in
     the development cycle, this has been sitting in next getting some
     testing for a while now and has relevant acks from the archs, so it
     should be pretty well tested and fine, but is nonetheless the thing
     I'll be keeping my eye on most closely.

   - Of particular note with the random_get_entropy() improvements is
     MIPS, which, on CPUs that lack the c0 count register, will now
     combine the high-speed but short-cycle c0 random register with the
     lower-speed but long-cycle generic fallback path.

   - With random_get_entropy() now always returning something useful,
     the interrupt handler now collects entropy in a consistent
     construction.

   - Rather than comparing two samples of random_get_entropy() for the
     jitter dance, the algorithm now tests many samples, and uses the
     amount of differing ones to determine whether or not jitter entropy
     is usable and how laborious it must be. The problem with comparing
     only two samples was that if the cycle counter was extremely slow,
     but just so happened to be on the cusp of a change, the slowness
     wouldn't be detected. Taking many samples fixes that to some
     degree.

     This, combined with the other improvements to random_get_entropy(),
     should make future unification of /dev/random and /dev/urandom
     maybe more possible. At the very least, were we to attempt it again
     today (we're not), it wouldn't break any of Guenter's test rigs
     that broke when we tried it with 5.18. So, not today, but perhaps
     down the road, that's something we can revisit.

   - We attempt to reseed the RNG immediately upon waking up from system
     suspend or hibernation, making use of the various timestamps about
     suspend time and such available, as well as the usual inputs such
     as RDRAND when available.

   - Batched randomness now falls back to ordinary randomness before the
     RNG is initialized. This provides more consistent guarantees to the
     types of random numbers being returned by the various accessors.

   - The "pre-init injection" code is now gone for good. I suspect you
     in particular will be happy to read that, as I recall you
     expressing your distaste for it a few months ago. Instead, to avoid
     a "premature first" issue, while still allowing for maximal amount
     of entropy availability during system boot, the first 128 bits of
     estimated entropy are used immediately as it arrives, with the next
     128 bits being buffered. And, as before, after the RNG has been
     fully initialized, it winds up reseeding anyway a few seconds later
     in most cases. This resulted in a pretty big simplification of the
     initialization code and let us remove various ad-hoc mechanisms
     like the ugly crng_pre_init_inject().

   - The RNG no longer pretends to handle the "premature next" security
     model, something that various academics and other RNG designs have
     tried to care about in the past. After an interesting mailing list
     thread, these issues are thought to be a) mainly academic and not
     practical at all, and b) actively harming the real security of the
     RNG by delaying new entropy additions after a potential compromise,
     making a potentially bad situation even worse. As well, in the
     first place, our RNG never even properly handled the premature next
     issue, so removing an incomplete solution to a fake problem was
     particularly nice.

     This allowed for numerous other simplifications in the code, which
     is a lot cleaner as a consequence. If you didn't see it before,
     https://lore.kernel.org/lkml/YmlMGx6+uigkGiZ0@zx2c4.com/ may be a
     thread worth skimming through.

   - While the interrupt handler received a separate code path years ago
     that avoids locks by using per-cpu data structures and a faster
     mixing algorithm, in order to reduce interrupt latency, input and
     disk events that are triggered in hardirq handlers were still
     hitting locks and more expensive algorithms. Those are now
     redirected to use the faster per-cpu data structures.

   - Rather than having the fake-crypto almost-siphash-based random32
     implementation be used right and left, and in many places where
     cryptographically secure randomness is desirable, the batched
     entropy code is now fast enough to replace that.

   - As usual, numerous code quality and documentation cleanups. For
     example, the initialization state machine now uses enum symbolic
     constants instead of just hard coding numbers everywhere.

   - Since the RNG initializes once, and then is always initialized
     thereafter, a pretty heavy amount of code used during that
     initialization is never used again. It is now completely cordoned
     off using static branches and it winds up in the .text.unlikely
     section so that it doesn't reduce cache compactness after the RNG
     is ready.

   - A variety of functions meant for waiting on the RNG to be
     initialized were only used by vsprintf, and in not a particularly
     optimal way. Replacing that usage with a more ordinary setup made
     it possible to remove those functions.

   - A cleanup of how we warn userspace about the use of uninitialized
     /dev/urandom and uninitialized get_random_bytes() usage.
     Interestingly, with the change you merged for 5.18 that attempts to
     use jitter (but does not block if it can't), the majority of users
     should never see those warnings for /dev/urandom at all now, and
     the one for in-kernel usage is mainly a debug thing.

   - The file_operations struct for /dev/[u]random now implements
     .read_iter and .write_iter instead of .read and .write, allowing it
     to also implement .splice_read and .splice_write, which makes
     splice(2) work again after it was broken here (and in many other
     places in the tree) during the set_fs() removal. This was a bit of
     a last minute arrival from Jens that hasn't had as much time to
     bake, so I'll be keeping my eye on this as well, but it seems
     fairly ordinary. Unfortunately, read_iter() is around 3% slower
     than read() in my tests, which I'm not thrilled about. But Jens and
     Al, spurred by this observation, seem to be making progress in
     removing the bottlenecks on the iter paths in the VFS layer in
     general, which should remove the performance gap for all drivers.

   - Assorted other bug fixes, cleanups, and optimizations.

   - A small SipHash cleanup"

* tag 'random-5.19-rc1-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/crng/random: (49 commits)
  random: check for signals after page of pool writes
  random: wire up fops->splice_{read,write}_iter()
  random: convert to using fops->write_iter()
  random: convert to using fops->read_iter()
  random: unify batched entropy implementations
  random: move randomize_page() into mm where it belongs
  random: remove mostly unused async readiness notifier
  random: remove get_random_bytes_arch() and add rng_has_arch_random()
  random: move initialization functions out of hot pages
  random: make consistent use of buf and len
  random: use proper return types on get_random_{int,long}_wait()
  random: remove extern from functions in header
  random: use static branch for crng_ready()
  random: credit architectural init the exact amount
  random: handle latent entropy and command line from random_init()
  random: use proper jiffies comparison macro
  random: remove ratelimiting for in-kernel unseeded randomness
  random: move initialization out of reseeding hot path
  random: avoid initializing twice in credit race
  random: use symbolic constants for crng_init states
  ...
2022-05-24 11:58:10 -07:00
Linus Torvalds
6e01f86fb2 Updates for timers and timekeeping core code:
- Expose CLOCK_TAI to instrumentation to aid with TSN debugging.
 
   - Ensure that the clockevent is stopped when there is no timer armed to
     avoid pointless wakeups.
 
   - Make the sched clock frequency handling and rounding consistent.
 
   - Provide a better debugobject hint for delayed works. The timer callback
     is always the same, which makes it difficult to identify the underlying
     work. Use the work function as a hint instead.
 
   - Move the timer specific sysctl code into the timer subsystem.
 
   - The usual set of improvements and cleanups
 -----BEGIN PGP SIGNATURE-----
 
 iQJHBAABCgAxFiEEQp8+kY+LLUocC4bMphj1TA10mKEFAmKLPHMTHHRnbHhAbGlu
 dXRyb25peC5kZQAKCRCmGPVMDXSYoZBoEACIURtS8w9PFZ6q/2mFq0pTYi/uI/HQ
 vqbB6gCbrjfL6QwInd7jxDc/UoqEOllG9pTaGdWx/0Gi9syDosEbeop7cvvt2xi+
 pReoEN1kVI3JAVrQFIAuGw4EMuzYB8PfuZkm1PdozcCP9qkgDmtippVxe05sFQ+/
 RPdA29vE3g63eXkSFBhEID23pQR8yKLbqVq6KcH87OipZedL+2fry3yB+/9sLuuU
 /PFLbI6B9f43S2sfo6szzpFkpd6tJlBlu02IrB6gh4IxKrslmZb5onpvcf6iT+19
 rFh5A15GFWoZUC8EjH1sBpATq3wA/jfGEOPWgy07N5SmobtJvWSM5yvT+gC3qXqm
 C/bjyjqXzLKftG7KIXo/hWewtsjdovMbdfcMBsGiatytNBZfI1GR/4Pq60/qpTHZ
 qJo35trOUcP6o1njphwONy3lisq78S7xaozpWO1hIMTcAqGgBkm/lOieGMM4hGnE
 Ps0Im3ZsOXNGllulN+3h+UHstM5/y6f/vzBsw7pfIG66i6KqebAiNjbMfHCr22sX
 7UavNCoFggUQgZVgUYX/AscdW4/Dwx6R5YUqj1EBqztknd70Ac4TqjaIz4Xa6ZER
 z+eQSSt5XqqV2eKWA4FsQYmCIc+BvQ4apSA6+whz9vmsvCYtB7zzSfeh+xkgcl1/
 Cc0N6G5+L9v0Gw==
 =De28
 -----END PGP SIGNATURE-----

Merge tag 'timers-core-2022-05-23' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull timer and timekeeping updates from Thomas Gleixner:

 - Expose CLOCK_TAI to instrumentation to aid with TSN debugging.

 - Ensure that the clockevent is stopped when there is no timer armed to
   avoid pointless wakeups.

 - Make the sched clock frequency handling and rounding consistent.

 - Provide a better debugobject hint for delayed works. The timer
   callback is always the same, which makes it difficult to identify the
   underlying work. Use the work function as a hint instead.

 - Move the timer specific sysctl code into the timer subsystem.

 - The usual set of improvements and cleanups

* tag 'timers-core-2022-05-23' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  timers: Provide a better debugobjects hint for delayed works
  time/sched_clock: Fix formatting of frequency reporting code
  time/sched_clock: Use Hz as the unit for clock rate reporting below 4kHz
  time/sched_clock: Round the frequency reported to nearest rather than down
  timekeeping: Consolidate fast timekeeper
  timekeeping: Annotate ktime_get_boot_fast_ns() with data_race()
  timers/nohz: Switch to ONESHOT_STOPPED in the low-res handler when the tick is stopped
  timekeeping: Introduce fast accessor to clock tai
  tracing/timer: Add missing argument documentation of trace points
  clocksource: Replace cpumask_weight() with cpumask_empty()
  timers: Move timer sysctl into the timer code
  clockevents: Use dedicated list iterator variable
  timers: Simplify calc_index()
  timers: Initialize base::next_expiry_recalc in timers_prepare_cpu()
2022-05-23 17:05:55 -07:00
Jason A. Donenfeld
1366992e16 timekeeping: Add raw clock fallback for random_get_entropy()
The addition of random_get_entropy_fallback() provides access to
whichever time source has the highest frequency, which is useful for
gathering entropy on platforms without available cycle counters. It's
not necessarily as good as being able to quickly access a cycle counter
that the CPU has, but it's still something, even when it falls back to
being jiffies-based.

In the event that a given arch does not define get_cycles(), falling
back to the get_cycles() default implementation that returns 0 is really
not the best we can do. Instead, at least calling
random_get_entropy_fallback() would be preferable, because that always
needs to return _something_, even falling back to jiffies eventually.
It's not as though random_get_entropy_fallback() is super high precision
or guaranteed to be entropic, but basically anything that's not zero all
the time is better than returning zero all the time.

Finally, since random_get_entropy_fallback() is used during extremely
early boot when randomizing freelists in mm_init(), it can be called
before timekeeping has been initialized. In that case there really is
nothing we can do; jiffies hasn't even started ticking yet. So just give
up and return 0.

Suggested-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Theodore Ts'o <tytso@mit.edu>
2022-05-13 23:59:23 +02:00
Thomas Gleixner
90be8d6c1f timekeeping: Consolidate fast timekeeper
Provide a inline function which replaces the copy & pasta.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/20220415091921.072296632@linutronix.de
2022-05-02 14:00:20 +02:00
Thomas Gleixner
eff4849f92 timekeeping: Annotate ktime_get_boot_fast_ns() with data_race()
Accessing timekeeper::offset_boot in ktime_get_boot_fast_ns() is an
intended data race as the reader side cannot synchronize with a writer and
there is no space in struct tk_read_base of the NMI safe timekeeper.

Mark it so.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/20220415091920.956045162@linutronix.de
2022-05-02 14:00:20 +02:00
Kurt Kanzenbach
2c33d775ef timekeeping: Mark NMI safe time accessors as notrace
Mark the CLOCK_MONOTONIC fast time accessors as notrace. These functions are
used in tracing to retrieve timestamps, so they should not recurse.

Fixes: 4498e7467e ("time: Parametrize all tk_fast_mono users")
Fixes: f09cb9a180 ("time: Introduce tk_fast_raw")
Reported-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Kurt Kanzenbach <kurt@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/20220426175338.3807ca4f@gandalf.local.home/
Link: https://lore.kernel.org/r/20220428062432.61063-1-kurt@linutronix.de
2022-04-29 00:07:53 +02:00
Kurt Kanzenbach
3dc6ffae2d timekeeping: Introduce fast accessor to clock tai
Introduce fast/NMI safe accessor to clock tai for tracing. The Linux kernel
tracing infrastructure has support for using different clocks to generate
timestamps for trace events. Especially in TSN networks it's useful to have TAI
as trace clock, because the application scheduling is done in accordance to the
network time, which is based on TAI. With a tai trace_clock in place, it becomes
very convenient to correlate network activity with Linux kernel application
traces.

Use the same implementation as ktime_get_boot_fast_ns() does by reading the
monotonic time and adding the TAI offset. The same limitations as for the fast
boot implementation apply. The TAI offset may change at run time e.g., by
setting the time or using adjtimex() with an offset. However, these kind of
offset changes are rare events. Nevertheless, the user has to be aware and deal
with it in post processing.

An alternative approach would be to use the same implementation as
ktime_get_real_fast_ns() does. However, this requires to add an additional u64
member to the tk_read_base struct. This struct together with a seqcount is
designed to fit into a single cache line on 64 bit architectures. Adding a new
member would violate this constraint.

Signed-off-by: Kurt Kanzenbach <kurt@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Steven Rostedt <rostedt@goodmis.org>
Link: https://lore.kernel.org/r/20220414091805.89667-2-kurt@linutronix.de
2022-04-14 16:19:30 +02:00
Yu Liao
4e8c11b6b3 timekeeping: Really make sure wall_to_monotonic isn't positive
Even after commit e1d7ba8735 ("time: Always make sure wall_to_monotonic
isn't positive") it is still possible to make wall_to_monotonic positive
by running the following code:

    int main(void)
    {
        struct timespec time;

        clock_gettime(CLOCK_MONOTONIC, &time);
        time.tv_nsec = 0;
        clock_settime(CLOCK_REALTIME, &time);
        return 0;
    }

The reason is that the second parameter of timespec64_compare(), ts_delta,
may be unnormalized because the delta is calculated with an open coded
substraction which causes the comparison of tv_sec to yield the wrong
result:

  wall_to_monotonic = { .tv_sec = -10, .tv_nsec =  900000000 }
  ts_delta 	    = { .tv_sec =  -9, .tv_nsec = -900000000 }

That makes timespec64_compare() claim that wall_to_monotonic < ts_delta,
but actually the result should be wall_to_monotonic > ts_delta.

After normalization, the result of timespec64_compare() is correct because
the tv_sec comparison is not longer misleading:

  wall_to_monotonic = { .tv_sec = -10, .tv_nsec =  900000000 }
  ts_delta 	    = { .tv_sec = -10, .tv_nsec =  100000000 }

Use timespec64_sub() to ensure that ts_delta is normalized, which fixes the
issue.

Fixes: e1d7ba8735 ("time: Always make sure wall_to_monotonic isn't positive")
Signed-off-by: Yu Liao <liaoyu15@huawei.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/20211213135727.1656662-1-liaoyu15@huawei.com
2021-12-17 23:06:22 +01:00
Thomas Gleixner
17a1b8826b hrtimer: Add bases argument to clock_was_set()
clock_was_set() unconditionaly invokes retrigger_next_event() on all online
CPUs. This was necessary because that mechanism was also used for resume
from suspend to idle which is not longer the case.

The bases arguments allows the callers of clock_was_set() to hand in a mask
which tells clock_was_set() which of the hrtimer clock bases are affected
by the clock setting. This mask will be used in the next step to check
whether a CPU base has timers queued on a clock base affected by the event
and avoid the SMP function call if there are none.

Add a @bases argument, provide defines for the active bases masking and
fixup all callsites.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/20210713135158.691083465@linutronix.de
2021-08-10 17:57:23 +02:00
Thomas Gleixner
1b267793f4 time/timekeeping: Avoid invoking clock_was_set() twice
do_adjtimex() might end up scheduling a delayed clock_was_set() via
timekeeping_advance() and then invoke clock_was_set() directly which is
pointless.

Make timekeeping_advance() return whether an invocation of clock_was_set()
is required and handle it at the call sites which allows do_adjtimex() to
issue a single direct call if required.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/20210713135158.580966888@linutronix.de
2021-08-10 17:57:23 +02:00
Thomas Gleixner
a761a67f59 timekeeping: Distangle resume and clock-was-set events
Resuming timekeeping is a clock-was-set event and uses the clock-was-set
notification mechanism. This is in the way of making the clock-was-set
update for hrtimers selective so unnecessary IPIs are avoided when a CPU
base does not have timers queued which are affected by the clock setting.

Distangle it by invoking hrtimer_resume() on each unfreezing CPU and invoke
the new timerfd_resume() function from timekeeping_resume() which is the
only place where this is needed.

Rename hrtimer_resume() to hrtimer_resume_local() to reflect the change.

With this the clock_was_set*() functions are not longer required to IPI all
CPUs unconditionally and can get some smarts to avoid them.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/20210713135158.488853478@linutronix.de
2021-08-10 17:57:23 +02:00
Linus Torvalds
152d32aa84 ARM:
- Stage-2 isolation for the host kernel when running in protected mode
 
 - Guest SVE support when running in nVHE mode
 
 - Force W^X hypervisor mappings in nVHE mode
 
 - ITS save/restore for guests using direct injection with GICv4.1
 
 - nVHE panics now produce readable backtraces
 
 - Guest support for PTP using the ptp_kvm driver
 
 - Performance improvements in the S2 fault handler
 
 x86:
 
 - Optimizations and cleanup of nested SVM code
 
 - AMD: Support for virtual SPEC_CTRL
 
 - Optimizations of the new MMU code: fast invalidation,
   zap under read lock, enable/disably dirty page logging under
   read lock
 
 - /dev/kvm API for AMD SEV live migration (guest API coming soon)
 
 - support SEV virtual machines sharing the same encryption context
 
 - support SGX in virtual machines
 
 - add a few more statistics
 
 - improved directed yield heuristics
 
 - Lots and lots of cleanups
 
 Generic:
 
 - Rework of MMU notifier interface, simplifying and optimizing
 the architecture-specific code
 
 - Some selftests improvements
 -----BEGIN PGP SIGNATURE-----
 
 iQFIBAABCAAyFiEE8TM4V0tmI4mGbHaCv/vSX3jHroMFAmCJ13kUHHBib256aW5p
 QHJlZGhhdC5jb20ACgkQv/vSX3jHroM1HAgAqzPxEtiTPTFeFJV5cnPPJ3dFoFDK
 y/juZJUQ1AOtvuWzzwuf175ewkv9vfmtG6rVohpNSkUlJYeoc6tw7n8BTTzCVC1b
 c/4Dnrjeycr6cskYlzaPyV6MSgjSv5gfyj1LA5UEM16LDyekmaynosVWY5wJhju+
 Bnyid8l8Utgz+TLLYogfQJQECCrsU0Wm//n+8TWQgLf1uuiwshU5JJe7b43diJrY
 +2DX+8p9yWXCTz62sCeDWNahUv8AbXpMeJ8uqZPYcN1P0gSEUGu8xKmLOFf9kR7b
 M4U1Gyz8QQbjd2lqnwiWIkvRLX6gyGVbq2zH0QbhUe5gg3qGUX7JjrhdDQ==
 =AXUi
 -----END PGP SIGNATURE-----

Merge tag 'for-linus' of git://git.kernel.org/pub/scm/virt/kvm/kvm

Pull kvm updates from Paolo Bonzini:
 "This is a large update by KVM standards, including AMD PSP (Platform
  Security Processor, aka "AMD Secure Technology") and ARM CoreSight
  (debug and trace) changes.

  ARM:

   - CoreSight: Add support for ETE and TRBE

   - Stage-2 isolation for the host kernel when running in protected
     mode

   - Guest SVE support when running in nVHE mode

   - Force W^X hypervisor mappings in nVHE mode

   - ITS save/restore for guests using direct injection with GICv4.1

   - nVHE panics now produce readable backtraces

   - Guest support for PTP using the ptp_kvm driver

   - Performance improvements in the S2 fault handler

  x86:

   - AMD PSP driver changes

   - Optimizations and cleanup of nested SVM code

   - AMD: Support for virtual SPEC_CTRL

   - Optimizations of the new MMU code: fast invalidation, zap under
     read lock, enable/disably dirty page logging under read lock

   - /dev/kvm API for AMD SEV live migration (guest API coming soon)

   - support SEV virtual machines sharing the same encryption context

   - support SGX in virtual machines

   - add a few more statistics

   - improved directed yield heuristics

   - Lots and lots of cleanups

  Generic:

   - Rework of MMU notifier interface, simplifying and optimizing the
     architecture-specific code

   - a handful of "Get rid of oprofile leftovers" patches

   - Some selftests improvements"

* tag 'for-linus' of git://git.kernel.org/pub/scm/virt/kvm/kvm: (379 commits)
  KVM: selftests: Speed up set_memory_region_test
  selftests: kvm: Fix the check of return value
  KVM: x86: Take advantage of kvm_arch_dy_has_pending_interrupt()
  KVM: SVM: Skip SEV cache flush if no ASIDs have been used
  KVM: SVM: Remove an unnecessary prototype declaration of sev_flush_asids()
  KVM: SVM: Drop redundant svm_sev_enabled() helper
  KVM: SVM: Move SEV VMCB tracking allocation to sev.c
  KVM: SVM: Explicitly check max SEV ASID during sev_hardware_setup()
  KVM: SVM: Unconditionally invoke sev_hardware_teardown()
  KVM: SVM: Enable SEV/SEV-ES functionality by default (when supported)
  KVM: SVM: Condition sev_enabled and sev_es_enabled on CONFIG_KVM_AMD_SEV=y
  KVM: SVM: Append "_enabled" to module-scoped SEV/SEV-ES control variables
  KVM: SEV: Mask CPUID[0x8000001F].eax according to supported features
  KVM: SVM: Move SEV module params/variables to sev.c
  KVM: SVM: Disable SEV/SEV-ES if NPT is disabled
  KVM: SVM: Free sev_asid_bitmap during init if SEV setup fails
  KVM: SVM: Zero out the VMCB array used to track SEV ASID association
  x86/sev: Drop redundant and potentially misleading 'sev_enabled'
  KVM: x86: Move reverse CPUID helpers to separate header file
  KVM: x86: Rename GPR accessors to make mode-aware variants the defaults
  ...
2021-05-01 10:14:08 -07:00
Thomas Gleixner
b2c67cbe9f time: Add mechanism to recognize clocksource in time_get_snapshot
System time snapshots are not conveying information about the current
clocksource which was used, but callers like the PTP KVM guest
implementation have the requirement to evaluate the clocksource type to
select the appropriate mechanism.

Introduce a clocksource id field in struct clocksource which is by default
set to CSID_GENERIC (0). Clocksource implementations can set that field to
a value which allows to identify the clocksource.

Store the clocksource id of the current clocksource in the
system_time_snapshot so callers can evaluate which clocksource was used to
take the snapshot and act accordingly.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Jianyong Wu <jianyong.wu@arm.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20201209060932.212364-5-jianyong.wu@arm.com
2021-04-07 16:33:20 +01:00
Niklas Söderlund
d4c7c28806 timekeeping: Allow runtime PM from change_clocksource()
The struct clocksource callbacks enable() and disable() are described as a
way to allow clock sources to enter a power save mode. See commit
4614e6adaf ("clocksource: add enable() and disable() callbacks")

But using runtime PM from these callbacks triggers a cyclic lockdep warning when
switching clock source using change_clocksource().

  # echo e60f0000.timer > /sys/devices/system/clocksource/clocksource0/current_clocksource
   ======================================================
   WARNING: possible circular locking dependency detected
   ------------------------------------------------------
   migration/0/11 is trying to acquire lock:
   ffff0000403ed220 (&dev->power.lock){-...}-{2:2}, at: __pm_runtime_resume+0x40/0x74

   but task is already holding lock:
   ffff8000113c8f88 (tk_core.seq.seqcount){----}-{0:0}, at: multi_cpu_stop+0xa4/0x190

   which lock already depends on the new lock.

   the existing dependency chain (in reverse order) is:

   -> #2 (tk_core.seq.seqcount){----}-{0:0}:
          ktime_get+0x28/0xa0
          hrtimer_start_range_ns+0x210/0x2dc
          generic_sched_clock_init+0x70/0x88
          sched_clock_init+0x40/0x64
          start_kernel+0x494/0x524

   -> #1 (hrtimer_bases.lock){-.-.}-{2:2}:
          hrtimer_start_range_ns+0x68/0x2dc
          rpm_suspend+0x308/0x5dc
          rpm_idle+0xc4/0x2a4
          pm_runtime_work+0x98/0xc0
          process_one_work+0x294/0x6f0
          worker_thread+0x70/0x45c
          kthread+0x154/0x160
          ret_from_fork+0x10/0x20

   -> #0 (&dev->power.lock){-...}-{2:2}:
          _raw_spin_lock_irqsave+0x7c/0xc4
          __pm_runtime_resume+0x40/0x74
          sh_cmt_start+0x1c4/0x260
          sh_cmt_clocksource_enable+0x28/0x50
          change_clocksource+0x9c/0x160
          multi_cpu_stop+0xa4/0x190
          cpu_stopper_thread+0x90/0x154
          smpboot_thread_fn+0x244/0x270
          kthread+0x154/0x160
          ret_from_fork+0x10/0x20

   other info that might help us debug this:

   Chain exists of:
     &dev->power.lock --> hrtimer_bases.lock --> tk_core.seq.seqcount

    Possible unsafe locking scenario:

          CPU0                    CPU1
          ----                    ----
     lock(tk_core.seq.seqcount);
                                  lock(hrtimer_bases.lock);
                                  lock(tk_core.seq.seqcount);
     lock(&dev->power.lock);

    *** DEADLOCK ***

   2 locks held by migration/0/11:
    #0: ffff8000113c9278 (timekeeper_lock){-.-.}-{2:2}, at: change_clocksource+0x2c/0x160
    #1: ffff8000113c8f88 (tk_core.seq.seqcount){----}-{0:0}, at: multi_cpu_stop+0xa4/0x190

Rework change_clocksource() so it enables the new clocksource and disables
the old clocksource outside of the timekeeper_lock and seqcount write held
region. There is no requirement that these callbacks are invoked from the
lock held region.

Signed-off-by: Niklas Söderlund <niklas.soderlund+renesas@ragnatech.se>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Link: https://lore.kernel.org/r/20210211134318.323910-1-niklas.soderlund+renesas@ragnatech.se
2021-03-29 16:41:59 +02:00
Ingo Molnar
4bf07f6562 timekeeping, clocksource: Fix various typos in comments
Fix ~56 single-word typos in timekeeping & clocksource code comments.

Signed-off-by: Ingo Molnar <mingo@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: John Stultz <john.stultz@linaro.org>
Cc: Stephen Boyd <sboyd@kernel.org>
Cc: Daniel Lezcano <daniel.lezcano@linaro.org>
Cc: linux-kernel@vger.kernel.org
2021-03-22 23:06:48 +01:00
Chunguang Xu
aba428a0c6 timekeeping: Remove unused get_seconds()
The get_seconds() cleanup seems to have been completed, now it is
time to delete the legacy interface to avoid misuse later.

Signed-off-by: Chunguang Xu <brookxu@tencent.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/1606816351-26900-1-git-send-email-brookxu@tencent.com
2021-01-12 21:13:01 +01:00
Linus Torvalds
7a932e5702 asm-generic: cross-architecture timer cleanup
This cleans up two ancient timer features that were never completed in
 the past, CONFIG_GENERIC_CLOCKEVENTS and CONFIG_ARCH_USES_GETTIMEOFFSET.
 
 There was only one user left for the ARCH_USES_GETTIMEOFFSET variant
 of clocksource implementations, the ARM EBSA110 platform. Rather than
 changing to use modern timekeeping, we remove the platform entirely as
 Russell no longer uses his machine and nobody else seems to have one
 any more.
 
 The conditional code for using arch_gettimeoffset() is removed as
 a result.
 
 For CONFIG_GENERIC_CLOCKEVENTS, there are still a couple of platforms
 not using clockevent drivers: parisc, ia64, most of m68k, and one
 Arm platform. These all do timer ticks slighly differently, and this
 gets cleaned up to the point they at least all call the same helper
 function. Instead of most platforms using 'select GENERIC_CLOCKEVENTS'
 in Kconfig, the polarity is now reversed, with the few remaining ones
 selecting LEGACY_TIMER_TICK instead.
 
 Signed-off-by: Arnd Bergmann <arnd@arndb.de>
 -----BEGIN PGP SIGNATURE-----
 
 iQIzBAABCgAdFiEEo6/YBQwIrVS28WGKmmx57+YAGNkFAl/Y1v8ACgkQmmx57+YA
 GNmCvQ/9EDlgCt92r8SB+LGafDtgB8TUQZeIrs9S2mByzdxwnw0lxObIXFCnhQgh
 RpG3dR+ONRDnC5eI149B377JOEFMZWe2+BtYHUHkFARtUEWatslQcz7yAGvVRK/l
 TS/qReb6piKltlzuanF1bMZbjy2OhlaDRcm+OlC3y5mALR33M4emb+rJ6cSdfk3K
 v1iZhrxtfQT77ztesh/oPkPiyQ6kNcz7SfpyYOb6f5VLlml2BZ7YwBSVyGY7urHk
 RL3XqOUP4KKlMEAI8w0E2nvft6Fk+luziBhrMYWK0GvbmI1OESENuX/c6tgT2OQ1
 DRaVHvcPG/EAY8adOKxxVyHhEJDSoz5GJV/EtjlOegsJk6RomczR1uuiT3Kvm7Ah
 PktMKv4xQht1E15KPSKbOvNIEP18w2s5z6gw+jVDv8pw42pVEQManm1D+BICqrhl
 fcpw6T1drf9UxAjwX4+zXtmNs+a+mqiFG8puU4VVgT4GpQ8umHvunXz2WUjZO0jc
 3m8ErJHBvtJwW5TOHGyXnjl9SkwPzHOfF6IcXTYWEDU4/gQIK9TwUvCjLc0lE27t
 FMCV2ds7/K1CXwRgpa5IrefSkb8yOXSbRZ56NqqF7Ekxw4J5bYRSaY7jb+qD/e+3
 5O1y+iPxFrpH+16hSahvzrtcdFNbLQvBBuRtEQOYuHLt2UJrNoU=
 =QpNs
 -----END PGP SIGNATURE-----

Merge tag 'asm-generic-timers-5.11' of git://git.kernel.org/pub/scm/linux/kernel/git/arnd/asm-generic

Pull asm-generic cross-architecture timer cleanup from Arnd Bergmann:
 "This cleans up two ancient timer features that were never completed in
  the past, CONFIG_GENERIC_CLOCKEVENTS and CONFIG_ARCH_USES_GETTIMEOFFSET.

  There was only one user left for the ARCH_USES_GETTIMEOFFSET variant
  of clocksource implementations, the ARM EBSA110 platform. Rather than
  changing to use modern timekeeping, we remove the platform entirely as
  Russell no longer uses his machine and nobody else seems to have one
  any more.

  The conditional code for using arch_gettimeoffset() is removed as a
  result.

  For CONFIG_GENERIC_CLOCKEVENTS, there are still a couple of platforms
  not using clockevent drivers: parisc, ia64, most of m68k, and one Arm
  platform. These all do timer ticks slighly differently, and this gets
  cleaned up to the point they at least all call the same helper
  function.

  Instead of most platforms using 'select GENERIC_CLOCKEVENTS' in
  Kconfig, the polarity is now reversed, with the few remaining ones
  selecting LEGACY_TIMER_TICK instead"

* tag 'asm-generic-timers-5.11' of git://git.kernel.org/pub/scm/linux/kernel/git/arnd/asm-generic:
  timekeeping: default GENERIC_CLOCKEVENTS to enabled
  timekeeping: remove xtime_update
  m68k: remove timer_interrupt() function
  m68k: change remaining timers to legacy_timer_tick
  m68k: m68328: use legacy_timer_tick()
  m68k: sun3/sun3c: use legacy_timer_tick
  m68k: split heartbeat out of timer function
  m68k: coldfire: use legacy_timer_tick()
  parisc: use legacy_timer_tick
  ARM: rpc: use legacy_timer_tick
  ia64: convert to legacy_timer_tick
  timekeeping: add CONFIG_LEGACY_TIMER_TICK
  timekeeping: remove arch_gettimeoffset
  net: remove am79c961a driver
  ARM: remove ebsa110 platform
2020-12-16 00:07:17 -08:00
Alex Shi
6e5a91901c timekeeping: Address parameter documentation issues for various functions
The kernel-doc parser complains:

 kernel/time/timekeeping.c:1543: warning: Function parameter or member
 'ts' not described in 'read_persistent_clock64'

 kernel/time/timekeeping.c:764: warning: Function parameter or member
 'tk' not described in 'timekeeping_forward_now'

 kernel/time/timekeeping.c:1331: warning: Function parameter or member
 'ts' not described in 'timekeeping_inject_offset'

 kernel/time/timekeeping.c:1331: warning: Excess function parameter 'tv'
 description in 'timekeeping_inject_offset'

Add the missing parameter documentations and rename the 'tv' parameter of
timekeeping_inject_offset() to 'ts' so it matches the implemention.

[ tglx: Reworded a few docs and massaged changelog ]

Signed-off-by: Alex Shi <alex.shi@linux.alibaba.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/1605252275-63652-5-git-send-email-alex.shi@linux.alibaba.com
2020-11-15 23:47:24 +01:00
Alex Shi
29efc4612a timekeeping: Fix parameter docs of read_persistent_wall_and_boot_offset()
Address the following kernel-doc markup warnings:

 kernel/time/timekeeping.c:1563: warning: Function parameter or member
 'wall_time' not described in 'read_persistent_wall_and_boot_offset'
 kernel/time/timekeeping.c:1563: warning: Function parameter or member
 'boot_offset' not described in 'read_persistent_wall_and_boot_offset'

The parameters are described but miss the leading '@' and the colon after
the parameter names.

[ tglx: Massaged changelog ]

Signed-off-by: Alex Shi <alex.shi@linux.alibaba.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/1605252275-63652-6-git-send-email-alex.shi@linux.alibaba.com
2020-11-15 23:47:24 +01:00
Alex Shi
f27f7c3f10 timekeeping: Add missing parameter docs for pvclock_gtod_[un]register_notifier()
The kernel-doc parser complains about:
 kernel/time/timekeeping.c:651: warning: Function parameter or member
 'nb' not described in 'pvclock_gtod_register_notifier'
 kernel/time/timekeeping.c:670: warning: Function parameter or member
 'nb' not described in 'pvclock_gtod_unregister_notifier'

Add the missing parameter explanations.

[ tglx: Massaged changelog ]

Signed-off-by: Alex Shi <alex.shi@linux.alibaba.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/1605252275-63652-3-git-send-email-alex.shi@linux.alibaba.com
2020-11-15 23:47:24 +01:00
Thomas Gleixner
c1ce406e80 timekeeping: Fix up function documentation for the NMI safe accessors
Alex reported the following warning:

 kernel/time/timekeeping.c:464: warning: Function parameter or member
 'tkf' not described in '__ktime_get_fast_ns'

which is not entirely correct because the documented function is
ktime_get_mono_fast_ns() which does not have a parameter, but the
kernel-doc parser looks at the function declaration which follows the
comment and complains about the missing parameter documentation.

Aside of that the documentation for the rest of the NMI safe accessors is
either incomplete or missing.

  - Move the function documentation to the right place
  - Fixup the references and inconsistencies
  - Add the missing documentation for ktime_get_raw_fast_ns()

Reported-by: Alex Shi <alex.shi@linux.alibaba.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2020-11-15 23:47:24 +01:00
Alex Shi
e025b03113 timekeeping: Add missing parameter documentation for update_fast_timekeeper()
Address the following warning:

 kernel/time/timekeeping.c:415: warning: Function parameter or member
 'tkf' not described in 'update_fast_timekeeper'

[ tglx: Remove the bogus ktime_get_mono_fast_ns() part ]

Signed-off-by: Alex Shi <alex.shi@linux.alibaba.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/1605252275-63652-2-git-send-email-alex.shi@linux.alibaba.com
2020-11-15 23:47:24 +01:00
Alex Shi
199d280c88 timekeeping: Remove static functions from kernel-doc markup
Various static functions in the timekeeping code have function comments
which pretend to be kernel-doc, but are incomplete and trigger parser
warnings.

As these functions are local to the timekeeping core code there is no need
to expose them via kernel-doc.

Remove the double star kernel-doc marker and remove excess newlines.

[ tglx: Massaged changelog and removed excess newlines ]

Signed-off-by: Alex Shi <alex.shi@linux.alibaba.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/1605252275-63652-4-git-send-email-alex.shi@linux.alibaba.com
2020-11-15 23:47:23 +01:00
Arnd Bergmann
56cc7b8acf timekeeping: remove xtime_update
There are no more users of xtime_update aside from legacy_timer_tick(),
so fold it into that function and remove the declaration.

update_process_times() is now only called inside of the kernel/time/
code, so the declaration can be moved there.

Reviewed-by: Geert Uytterhoeven <geert@linux-m68k.org>
Tested-by: Geert Uytterhoeven <geert@linux-m68k.org>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
2020-10-30 21:57:07 +01:00
Arnd Bergmann
77f6c0b874 timekeeping: remove arch_gettimeoffset
With Arm EBSA110 gone, nothing uses it any more, so the corresponding
code and the Kconfig option can be removed.

Acked-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
2020-10-30 21:57:04 +01:00
Linus Torvalds
ed016af52e These are the locking updates for v5.10:
- Add deadlock detection for recursive read-locks. The rationale is outlined
    in:
 
      224ec489d3: ("lockdep/Documention: Recursive read lock detection reasoning")
 
    The main deadlock pattern we want to detect is:
 
            TASK A:                 TASK B:
 
            read_lock(X);
                                    write_lock(X);
            read_lock_2(X);
 
  - Add "latch sequence counters" (seqcount_latch_t):
 
       A sequence counter variant where the counter even/odd value is used to
       switch between two copies of protected data. This allows the read path,
       typically NMIs, to safely interrupt the write side critical section.
 
    We utilize this new variant for sched-clock, and to make x86 TSC handling safer.
 
  - Other seqlock cleanups, fixes and enhancements
 
  - KCSAN updates
 
  - LKMM updates
 
  - Misc updates, cleanups and fixes.
 
 Signed-off-by: Ingo Molnar <mingo@kernel.org>
 -----BEGIN PGP SIGNATURE-----
 
 iQJFBAABCgAvFiEEBpT5eoXrXCwVQwEKEnMQ0APhK1gFAl+EX6QRHG1pbmdvQGtl
 cm5lbC5vcmcACgkQEnMQ0APhK1g3gxAAkg+Jy/tcdRxlxlEDOQPFy1mBqvFmulNA
 pGFPkB6dzqmAWF/NfOZSl4g/h/mqGYsq2V+PfK5E8Sq8DQ/yCmnLhjgVOHNUUliv
 x0WWfOysNgJdtdf69NLYJufIQhxhyI0dwFHHoHIsCdGdGqjh2DVevQFPFTBjdpOc
 BUZYo+u3gCaCdB6A2nmlcWYbEw8eVEHgv3qLG6dq46J0KJOV0HfliqJoU3EZqH+s
 977LvEIo+THfuYWMo/Jepwngbi0y36KeeukOAdwm9fK196htBHIUR+YPPrAe+FWD
 z+UXP5IS5XIw9V1sGLmUaC2m+6gpdW19jKBtlzPkxHXmJmsgiZdLLeytEh3WYey7
 nzfH+9Jd4NyyZKucLssYkOjf6P5BxGKCyJ9LXb7vlSthIhiDdFNx47oKtW4hxjOY
 jubsI3BP5c3G1sIBIjTS53XmOhJg+Z52FxTpQ33JswXn1wGidcHZiuNHZuU5q28p
 +tn8rGb2NGJFb4Sw/Vp0yTcqIpEXf+vweiQoaxm6tc9BWzcVzZntGnh0i3gFotx/
 VgKafN4+pgXgo6bwHbN2WBK2FGyvcXFaptfaOMZL48En82hJ1DI6EnBEYN+vuERQ
 JcCXg+iHeeVbxoou7q8NJxITkBmEL5xNBIugXRRqNSP3fXLxKjFuPYqT84/e7yZi
 elGTReYcq6g=
 =Iq51
 -----END PGP SIGNATURE-----

Merge tag 'locking-core-2020-10-12' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull locking updates from Ingo Molnar:
 "These are the locking updates for v5.10:

   - Add deadlock detection for recursive read-locks.

     The rationale is outlined in commit 224ec489d3 ("lockdep/
     Documention: Recursive read lock detection reasoning")

     The main deadlock pattern we want to detect is:

           TASK A:                 TASK B:

           read_lock(X);
                                   write_lock(X);
           read_lock_2(X);

   - Add "latch sequence counters" (seqcount_latch_t):

     A sequence counter variant where the counter even/odd value is used
     to switch between two copies of protected data. This allows the
     read path, typically NMIs, to safely interrupt the write side
     critical section.

     We utilize this new variant for sched-clock, and to make x86 TSC
     handling safer.

   - Other seqlock cleanups, fixes and enhancements

   - KCSAN updates

   - LKMM updates

   - Misc updates, cleanups and fixes"

* tag 'locking-core-2020-10-12' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (67 commits)
  lockdep: Revert "lockdep: Use raw_cpu_*() for per-cpu variables"
  lockdep: Fix lockdep recursion
  lockdep: Fix usage_traceoverflow
  locking/atomics: Check atomic-arch-fallback.h too
  locking/seqlock: Tweak DEFINE_SEQLOCK() kernel doc
  lockdep: Optimize the memory usage of circular queue
  seqlock: Unbreak lockdep
  seqlock: PREEMPT_RT: Do not starve seqlock_t writers
  seqlock: seqcount_LOCKNAME_t: Introduce PREEMPT_RT support
  seqlock: seqcount_t: Implement all read APIs as statement expressions
  seqlock: Use unique prefix for seqcount_t property accessors
  seqlock: seqcount_LOCKNAME_t: Standardize naming convention
  seqlock: seqcount latch APIs: Only allow seqcount_latch_t
  rbtree_latch: Use seqcount_latch_t
  x86/tsc: Use seqcount_latch_t
  timekeeping: Use seqcount_latch_t
  time/sched_clock: Use seqcount_latch_t
  seqlock: Introduce seqcount_latch_t
  mm/swap: Do not abuse the seqcount_t latching API
  time/sched_clock: Use raw_read_seqcount_latch() during suspend
  ...
2020-10-12 13:06:20 -07:00
Ahmed S. Darwish
249d053835 timekeeping: Use seqcount_latch_t
Latch sequence counters are a multiversion concurrency control mechanism
where the seqcount_t counter even/odd value is used to switch between
two data storage copies. This allows the seqcount_t read path to safely
interrupt its write side critical section (e.g. from NMIs).

Initially, latch sequence counters were implemented as a single write
function, raw_write_seqcount_latch(), above plain seqcount_t. The read
path was expected to use plain seqcount_t raw_read_seqcount().

A specialized read function was later added, raw_read_seqcount_latch(),
and became the standardized way for latch read paths. Having unique read
and write APIs meant that latch sequence counters are basically a data
type of their own -- just inappropriately overloading plain seqcount_t.
The seqcount_latch_t data type was thus introduced at seqlock.h.

Use that new data type instead of seqcount_raw_spinlock_t. This ensures
that only latch-safe APIs are to be used with the sequence counter.

Note that the use of seqcount_raw_spinlock_t was not very useful in the
first place. Only the "raw_" subset of seqcount_t APIs were used at
timekeeping.c. This subset was created for contexts where lockdep cannot
be used. seqcount_LOCKTYPE_t's raison d'être -- verifying that the
seqcount_t writer serialization lock is held -- cannot thus be done.

References: 0c3351d451 ("seqlock: Use raw_ prefix instead of _no_lockdep")
References: 55f3560df9 ("seqlock: Extend seqcount API with associated locks")
Signed-off-by: Ahmed S. Darwish <a.darwish@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20200827114044.11173-6-a.darwish@linutronix.de
2020-09-10 11:19:29 +02:00
Thomas Gleixner
e2d977c9f1 timekeeping: Provide multi-timestamp accessor to NMI safe timekeeper
printk wants to store various timestamps (MONOTONIC, REALTIME, BOOTTIME) to
make correlation of dmesg from several systems easier.

Provide an interface to retrieve all three timestamps in one go.

There are some caveats:

1) Boot time and late sleep time injection

  Boot time is a racy access on 32bit systems if the sleep time injection
  happens late during resume and not in timekeeping_resume(). That could be
  avoided by expanding struct tk_read_base with boot offset for 32bit and
  adding more overhead to the update. As this is a hard to observe once per
  resume event which can be filtered with reasonable effort using the
  accurate mono/real timestamps, it's probably not worth the trouble.

  Aside of that it might be possible on 32 and 64 bit to observe the
  following when the sleep time injection happens late:

  CPU 0				         CPU 1
  timekeeping_resume()
  ktime_get_fast_timestamps()
    mono, real = __ktime_get_real_fast()
  					 inject_sleep_time()
  					   update boot offset
  	boot = mono + bootoffset;
  
  That means that boot time already has the sleep time adjustment, but
  real time does not. On the next readout both are in sync again.
  
  Preventing this for 64bit is not really feasible without destroying the
  careful cache layout of the timekeeper because the sequence count and
  struct tk_read_base would then need two cache lines instead of one.

2) Suspend/resume timestamps

   Access to the time keeper clock source is disabled accross the innermost
   steps of suspend/resume. The accessors still work, but the timestamps
   are frozen until time keeping is resumed which happens very early.

   For regular suspend/resume there is no observable difference vs. sched
   clock, but it might affect some of the nasty low level debug printks.

   OTOH, access to sched clock is not guaranteed accross suspend/resume on
   all systems either so it depends on the hardware in use.

   If that turns out to be a real problem then this could be mitigated by
   using sched clock in a similar way as during early boot. But it's not as
   trivial as on early boot because it needs some careful protection
   against the clock monotonic timestamp jumping backwards on resume.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Petr Mladek <pmladek@suse.com>                                                                                                                                                                                                                                      
Link: https://lore.kernel.org/r/20200814115512.159981360@linutronix.de
2020-08-23 10:38:24 +02:00
Thomas Gleixner
71419b30ca timekeeping: Utilize local_clock() for NMI safe timekeeper during early boot
During early boot the NMI safe timekeeper returns 0 until the first
clocksource becomes available.

This prevents it from being used for printk or other facilities which today
use sched clock. sched clock can be available way before timekeeping is
initialized.

The obvious workaround for this is to utilize the early sched clock in the
default dummy clock read function until a clocksource becomes available.

After switching to the clocksource clock MONOTONIC and BOOTTIME will not
jump because the timekeeping_init() bases clock MONOTONIC on sched clock
and the offset between clock MONOTONIC and BOOTTIME is zero during boot.

Clock REALTIME cannot provide useful timestamps during early boot up to
the point where a persistent clock becomes available, which is either in
timekeeping_init() or later when the RTC driver which might depend on I2C
or other subsystems is initialized.

There is a minor difference to sched_clock() vs. suspend/resume. As the
timekeeper clock source might not be accessible during suspend, after
timekeeping_suspend() timestamps freeze up to the point where
timekeeping_resume() is invoked. OTOH this is true for some sched clock
implementations as well.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Petr Mladek <pmladek@suse.com>                                                                                                                                                                                                                                      
Link: https://lore.kernel.org/r/20200814115512.041422402@linutronix.de
2020-08-23 10:38:24 +02:00
Linus Torvalds
b923f1247b A set oftimekeeping/VDSO updates:
- Preparatory work to allow S390 to switch over to the generic VDSO
    implementation.
 
    S390 requires that the VDSO data pointer is handed in to the counter
    read function when time namespace support is enabled. Adding the pointer
    is a NOOP for all other architectures because the compiler is supposed
    to optimize that out when it is unused in the architecture specific
    inline. The change also solved a similar problem for MIPS which
    fortunately has time namespaces not yet enabled.
 
    S390 needs to update clock related VDSO data independent of the
    timekeeping updates. This was solved so far with yet another sequence
    counter in the S390 implementation. A better solution is to utilize the
    already existing VDSO sequence count for this. The core code now exposes
    helper functions which allow to serialize against the timekeeper code
    and against concurrent readers.
 
    S390 needs extra data for their clock readout function. The initial
    common VDSO data structure did not provide a way to add that. It now has
    an embedded architecture specific struct embedded which defaults to an
    empty struct.
 
    Doing this now avoids tree dependencies and conflicts post rc1 and
    allows all other architectures which work on generic VDSO support to
    work from a common upstream base.
 
  - A trivial comment fix.
 -----BEGIN PGP SIGNATURE-----
 
 iQJHBAABCgAxFiEEQp8+kY+LLUocC4bMphj1TA10mKEFAl82tGYTHHRnbHhAbGlu
 dXRyb25peC5kZQAKCRCmGPVMDXSYoRkKD/9YEYlYPQ4omRNVNIJRnalBH6OB/GOk
 jTJ4RCvNP2ew6XtgEz5Yg1VqxrmJP4MLNCnMr7mQulfezUmslK0uJMlqZC4dgYth
 PUhliLyFi5PK+CKaY+2NFlZMAoE53YlJ2FVPq114FUW4ASVbucDPXpmhO22cc2Iu
 0RD3z9/+vQmA8lUqI6wPIFTC+euN+2kbkeZjt7BlkBAdiRBga5UnarFzetq0nWyc
 kcprQ2qZfGLYzRY6dRuvNLz27Ta7SAlVGOGUDpWr9MISLDFQzHwhVATDNFW3hLGT
 Fr5xNqStUVxxTzYkfCj/Podez0aR3por8bm9SoWxZn7oeLdLgTsDwn2pY0J0PjyB
 wWz9lmqT1vzrHEfQH1YhHvycowl6azue9rT2ERWwZTdbADEwu6Zr8ufv2XHcMu0J
 dyzSYa81cQrTeAwwdNjODs+QCTX+0G6u86AU2Xg+YgqkAywcAMvzcff/9D62hfv2
 5BSz+0OeitQCnSvHILUPw4XT/2rNZfhlcmc4tkzoBFewzDsMEqWT19p+GgqcRNiU
 5Jl4kGnaeHjP0e5Vn/ZJurKaF3YEJwgjkohDORloaqo0AXiYo1ANhDlKvSRu5hnU
 GDIWOVu8ATXwkjMFcLQz7O5/J1MqJCkleIjSCDjLDhhMbLY/nR9L3QS9jbqiVVRN
 nTZlSMF6HeQmew==
 =y8Z5
 -----END PGP SIGNATURE-----

Merge tag 'timers-urgent-2020-08-14' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull timekeeping updates from Thomas Gleixner:
 "A set of timekeeping/VDSO updates:

   - Preparatory work to allow S390 to switch over to the generic VDSO
     implementation.

     S390 requires that the VDSO data pointer is handed in to the
     counter read function when time namespace support is enabled.
     Adding the pointer is a NOOP for all other architectures because
     the compiler is supposed to optimize that out when it is unused in
     the architecture specific inline. The change also solved a similar
     problem for MIPS which fortunately has time namespaces not yet
     enabled.

     S390 needs to update clock related VDSO data independent of the
     timekeeping updates. This was solved so far with yet another
     sequence counter in the S390 implementation. A better solution is
     to utilize the already existing VDSO sequence count for this. The
     core code now exposes helper functions which allow to serialize
     against the timekeeper code and against concurrent readers.

     S390 needs extra data for their clock readout function. The initial
     common VDSO data structure did not provide a way to add that. It
     now has an embedded architecture specific struct embedded which
     defaults to an empty struct.

     Doing this now avoids tree dependencies and conflicts post rc1 and
     allows all other architectures which work on generic VDSO support
     to work from a common upstream base.

   - A trivial comment fix"

* tag 'timers-urgent-2020-08-14' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  time: Delete repeated words in comments
  lib/vdso: Allow to add architecture-specific vdso data
  timekeeping/vsyscall: Provide vdso_update_begin/end()
  vdso/treewide: Add vdso_data pointer argument to __arch_get_hw_counter()
2020-08-14 14:26:08 -07:00
Linus Torvalds
97d052ea3f A set of locking fixes and updates:
- Untangle the header spaghetti which causes build failures in various
     situations caused by the lockdep additions to seqcount to validate that
     the write side critical sections are non-preemptible.
 
   - The seqcount associated lock debug addons which were blocked by the
     above fallout.
 
     seqcount writers contrary to seqlock writers must be externally
     serialized, which usually happens via locking - except for strict per
     CPU seqcounts. As the lock is not part of the seqcount, lockdep cannot
     validate that the lock is held.
 
     This new debug mechanism adds the concept of associated locks.
     sequence count has now lock type variants and corresponding
     initializers which take a pointer to the associated lock used for
     writer serialization. If lockdep is enabled the pointer is stored and
     write_seqcount_begin() has a lockdep assertion to validate that the
     lock is held.
 
     Aside of the type and the initializer no other code changes are
     required at the seqcount usage sites. The rest of the seqcount API is
     unchanged and determines the type at compile time with the help of
     _Generic which is possible now that the minimal GCC version has been
     moved up.
 
     Adding this lockdep coverage unearthed a handful of seqcount bugs which
     have been addressed already independent of this.
 
     While generaly useful this comes with a Trojan Horse twist: On RT
     kernels the write side critical section can become preemtible if the
     writers are serialized by an associated lock, which leads to the well
     known reader preempts writer livelock. RT prevents this by storing the
     associated lock pointer independent of lockdep in the seqcount and
     changing the reader side to block on the lock when a reader detects
     that a writer is in the write side critical section.
 
  - Conversion of seqcount usage sites to associated types and initializers.
 -----BEGIN PGP SIGNATURE-----
 
 iQJHBAABCgAxFiEEQp8+kY+LLUocC4bMphj1TA10mKEFAl8xmPYTHHRnbHhAbGlu
 dXRyb25peC5kZQAKCRCmGPVMDXSYoTuQEACyzQCjU8PgehPp9oMqWzaX2fcVyuZO
 QU2yw6gmz2oTz3ZHUNwdW8UnzGh2OWosK3kDruoD9FtSS51lER1/ISfSPCGfyqxC
 KTjOcB1Kvxwq/3LcCx7Zi3ZxWApat74qs3EhYhKtEiQ2Y9xv9rLq8VV1UWAwyxq0
 eHpjlIJ6b6rbt+ARslaB7drnccOsdK+W/roNj4kfyt+gezjBfojGRdMGQNMFcpnv
 shuTC+vYurAVIiVA/0IuizgHfwZiXOtVpjVoEWaxg6bBH6HNuYMYzdSa/YrlDkZs
 n/aBI/Xkvx+Eacu8b1Zwmbzs5EnikUK/2dMqbzXKUZK61eV4hX5c2xrnr1yGWKTs
 F/juh69Squ7X6VZyKVgJ9RIccVueqwR2EprXWgH3+RMice5kjnXH4zURp0GHALxa
 DFPfB6fawcH3Ps87kcRFvjgm6FBo0hJ1AxmsW1dY4ACFB9azFa2euW+AARDzHOy2
 VRsUdhL9CGwtPjXcZ/9Rhej6fZLGBXKr8uq5QiMuvttp4b6+j9FEfBgD4S6h8csl
 AT2c2I9LcbWqyUM9P4S7zY/YgOZw88vHRuDH7tEBdIeoiHfrbSBU7EQ9jlAKq/59
 f+Htu2Io281c005g7DEeuCYvpzSYnJnAitj5Lmp/kzk2Wn3utY1uIAVszqwf95Ul
 81ppn2KlvzUK8g==
 =7Gj+
 -----END PGP SIGNATURE-----

Merge tag 'locking-urgent-2020-08-10' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull locking updates from Thomas Gleixner:
 "A set of locking fixes and updates:

   - Untangle the header spaghetti which causes build failures in
     various situations caused by the lockdep additions to seqcount to
     validate that the write side critical sections are non-preemptible.

   - The seqcount associated lock debug addons which were blocked by the
     above fallout.

     seqcount writers contrary to seqlock writers must be externally
     serialized, which usually happens via locking - except for strict
     per CPU seqcounts. As the lock is not part of the seqcount, lockdep
     cannot validate that the lock is held.

     This new debug mechanism adds the concept of associated locks.
     sequence count has now lock type variants and corresponding
     initializers which take a pointer to the associated lock used for
     writer serialization. If lockdep is enabled the pointer is stored
     and write_seqcount_begin() has a lockdep assertion to validate that
     the lock is held.

     Aside of the type and the initializer no other code changes are
     required at the seqcount usage sites. The rest of the seqcount API
     is unchanged and determines the type at compile time with the help
     of _Generic which is possible now that the minimal GCC version has
     been moved up.

     Adding this lockdep coverage unearthed a handful of seqcount bugs
     which have been addressed already independent of this.

     While generally useful this comes with a Trojan Horse twist: On RT
     kernels the write side critical section can become preemtible if
     the writers are serialized by an associated lock, which leads to
     the well known reader preempts writer livelock. RT prevents this by
     storing the associated lock pointer independent of lockdep in the
     seqcount and changing the reader side to block on the lock when a
     reader detects that a writer is in the write side critical section.

   - Conversion of seqcount usage sites to associated types and
     initializers"

* tag 'locking-urgent-2020-08-10' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (25 commits)
  locking/seqlock, headers: Untangle the spaghetti monster
  locking, arch/ia64: Reduce <asm/smp.h> header dependencies by moving XTP bits into the new <asm/xtp.h> header
  x86/headers: Remove APIC headers from <asm/smp.h>
  seqcount: More consistent seqprop names
  seqcount: Compress SEQCNT_LOCKNAME_ZERO()
  seqlock: Fold seqcount_LOCKNAME_init() definition
  seqlock: Fold seqcount_LOCKNAME_t definition
  seqlock: s/__SEQ_LOCKDEP/__SEQ_LOCK/g
  hrtimer: Use sequence counter with associated raw spinlock
  kvm/eventfd: Use sequence counter with associated spinlock
  userfaultfd: Use sequence counter with associated spinlock
  NFSv4: Use sequence counter with associated spinlock
  iocost: Use sequence counter with associated spinlock
  raid5: Use sequence counter with associated spinlock
  vfs: Use sequence counter with associated spinlock
  timekeeping: Use sequence counter with associated raw spinlock
  xfrm: policy: Use sequence counters with associated lock
  netfilter: nft_set_rbtree: Use sequence counter with associated rwlock
  netfilter: conntrack: Use sequence counter with associated spinlock
  sched: tasks: Use sequence counter with associated spinlock
  ...
2020-08-10 19:07:44 -07:00
Randy Dunlap
b0294f3025 time: Delete repeated words in comments
Drop repeated words in kernel/time/.  {when, one, into}

Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: John Stultz <john.stultz@linaro.org>
Link: https://lore.kernel.org/r/20200807033248.8452-1-rdunlap@infradead.org
2020-08-10 22:14:07 +02:00
Thomas Gleixner
19d0070a27 timekeeping/vsyscall: Provide vdso_update_begin/end()
Architectures can have the requirement to add additional architecture
specific data to the VDSO data page which needs to be updated independent
of the timekeeper updates.

To protect these updates vs. concurrent readers and a conflicting update
through timekeeping, provide helper functions to make such updates safe.

vdso_update_begin() takes the timekeeper_lock to protect against a
potential update from timekeeper code and increments the VDSO sequence
count to signal data inconsistency to concurrent readers. vdso_update_end()
makes the sequence count even again to signal data consistency and drops
the timekeeper lock.

[ Sven: Add interrupt disable handling to the functions ]

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Sven Schnelle <svens@linux.ibm.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lkml.kernel.org/r/20200804150124.41692-3-svens@linux.ibm.com
2020-08-06 10:57:30 +02:00
Ahmed S. Darwish
025e82bcbc timekeeping: Use sequence counter with associated raw spinlock
A sequence counter write side critical section must be protected by some
form of locking to serialize writers. A plain seqcount_t does not
contain the information of which lock must be held when entering a write
side critical section.

Use the new seqcount_raw_spinlock_t data type, which allows to associate
a raw spinlock with the sequence counter. This enables lockdep to verify
that the raw spinlock used for writer serialization is held when the
write side critical section is entered.

If lockdep is disabled this lock association is compiled out and has
neither storage size nor runtime overhead.

Signed-off-by: Ahmed S. Darwish <a.darwish@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20200720155530.1173732-18-a.darwish@linutronix.de
2020-07-29 16:14:27 +02:00
Paul Gortmaker
46132e3ac5 sched: nohz: stop passing around unused "ticks" parameter.
The "ticks" parameter was added in commit 0f004f5a69 ("sched: Cure more
NO_HZ load average woes") since calc_global_nohz() was called and needed
the "ticks" argument.

But in commit c308b56b53 ("sched: Fix nohz load accounting -- again!")
it became unused as the function calc_global_nohz() dropped using "ticks".

Fixes: c308b56b53 ("sched: Fix nohz load accounting -- again!")
Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/1593628458-32290-1-git-send-email-paul.gortmaker@windriver.com
2020-07-22 10:22:04 +02:00
Thomas Gleixner
865d3a9afe x86/mce: Address objtools noinstr complaints
Mark the relevant functions noinstr, use the plain non-instrumented MSR
accessors. The only odd part is the instrumentation_begin()/end() pair around the
indirect machine_check_vector() call as objtool can't figure that out. The
possible invoked functions are annotated correctly.

Also use notrace variant of nmi_enter/exit(). If MCEs happen then hardware
latency tracing is the least of the worries.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Alexandre Chartre <alexandre.chartre@oracle.com>
Acked-by: Peter Zijlstra <peterz@infradead.org>
Acked-by: Andy Lutomirski <luto@kernel.org>
Link: https://lkml.kernel.org/r/20200505135315.476734898@linutronix.de
2020-06-11 15:15:02 +02:00
Linus Torvalds
dbb381b619 timekeeping and timer updates:
Core:
 
   - Consolidation of the vDSO build infrastructure to address the
     difficulties of cross-builds for ARM64 compat vDSO libraries by
     restricting the exposure of header content to the vDSO build.
 
     This is achieved by splitting out header content into separate
     headers. which contain only the minimaly required information which is
     necessary to build the vDSO. These new headers are included from the
     kernel headers and the vDSO specific files.
 
   - Enhancements to the generic vDSO library allowing more fine grained
     control over the compiled in code, further reducing architecture
     specific storage and preparing for adopting the generic library by PPC.
 
   - Cleanup and consolidation of the exit related code in posix CPU timers.
 
   - Small cleanups and enhancements here and there
 
  Drivers:
 
   - The obligatory new drivers: Ingenic JZ47xx and X1000 TCU support
 
   - Correct the clock rate of PIT64b global clock
 
   - setup_irq() cleanup
 
   - Preparation for PWM and suspend support for the TI DM timer
 
   - Expand the fttmr010 driver to support ast2600 systems
 
   - The usual small fixes, enhancements and cleanups all over the place
 -----BEGIN PGP SIGNATURE-----
 
 iQJHBAABCgAxFiEEQp8+kY+LLUocC4bMphj1TA10mKEFAl6B+QETHHRnbHhAbGlu
 dXRyb25peC5kZQAKCRCmGPVMDXSYofJ5D/94s5fpaqiuNcaAsLq2D3DRIrTnqxx7
 yEeAOPcbYV1bM1SgY/M83L5yGc2S8ny787e26abwRTCZhZV3eAmRTphIFFIZR0Xk
 xS+i67odscbdJTRtztKj3uQ9rFxefszRuphyaa89pwSY9nnyMWLcahGSQOGs0LJK
 hvmgwPjyM1drNfPxgPiaFg7vDr2XxNATpQr/FBt+BhelvVan8TlAfrkcNPiLr++Y
 Axz925FP7jMaRRbZ1acji34gLiIAZk0jLCUdbix7YkPrqDB4GfO+v8Vez+fGClbJ
 uDOYeR4r1+Be/BtSJtJ2tHqtsKCcAL6agtaE2+epZq5HbzaZFRvBFaxgFNF8WVcn
 3FFibdEMdsRNfZTUVp5wwgOLN0UIqE/7LifE12oLEL2oFB5H2PiNEUw3E02XHO11
 rL3zgHhB6Ke1sXKPCjSGdmIQLbxZmV5kOlQFy7XuSeo5fmRapVzKNffnKcftIliF
 1HNtZbgdA+3tdxMFCqoo1QX+kotl9kgpslmdZ0qHAbaRb3xqLoSskbqEjFRMuSCC
 8bjJrwboD9T5GPfwodSCgqs/58CaSDuqPFbIjCay+p90Fcg6wWAkZtyG04ZLdPRc
 GgNNdN4gjTD9bnrRi8cH47z1g8OO4vt4K4SEbmjo8IlDW+9jYMxuwgR88CMeDXd7
 hu7aKsr2I2q/WQ==
 =5o9G
 -----END PGP SIGNATURE-----

Merge tag 'timers-core-2020-03-30' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull timekeeping and timer updates from Thomas Gleixner:
 "Core:

   - Consolidation of the vDSO build infrastructure to address the
     difficulties of cross-builds for ARM64 compat vDSO libraries by
     restricting the exposure of header content to the vDSO build.

     This is achieved by splitting out header content into separate
     headers. which contain only the minimaly required information which
     is necessary to build the vDSO. These new headers are included from
     the kernel headers and the vDSO specific files.

   - Enhancements to the generic vDSO library allowing more fine grained
     control over the compiled in code, further reducing architecture
     specific storage and preparing for adopting the generic library by
     PPC.

   - Cleanup and consolidation of the exit related code in posix CPU
     timers.

   - Small cleanups and enhancements here and there

  Drivers:

   - The obligatory new drivers: Ingenic JZ47xx and X1000 TCU support

   - Correct the clock rate of PIT64b global clock

   - setup_irq() cleanup

   - Preparation for PWM and suspend support for the TI DM timer

   - Expand the fttmr010 driver to support ast2600 systems

   - The usual small fixes, enhancements and cleanups all over the
     place"

* tag 'timers-core-2020-03-30' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (80 commits)
  Revert "clocksource/drivers/timer-probe: Avoid creating dead devices"
  vdso: Fix clocksource.h macro detection
  um: Fix header inclusion
  arm64: vdso32: Enable Clang Compilation
  lib/vdso: Enable common headers
  arm: vdso: Enable arm to use common headers
  x86/vdso: Enable x86 to use common headers
  mips: vdso: Enable mips to use common headers
  arm64: vdso32: Include common headers in the vdso library
  arm64: vdso: Include common headers in the vdso library
  arm64: Introduce asm/vdso/processor.h
  arm64: vdso32: Code clean up
  linux/elfnote.h: Replace elf.h with UAPI equivalent
  scripts: Fix the inclusion order in modpost
  common: Introduce processor.h
  linux/ktime.h: Extract common header for vDSO
  linux/jiffies.h: Extract common header for vDSO
  linux/time64.h: Extract common header for vDSO
  linux/time32.h: Extract common header for vDSO
  linux/time.h: Extract common header for vDSO
  ...
2020-03-30 18:51:47 -07:00
Thomas Gleixner
e5d4d1756b timekeeping: Split jiffies seqlock
seqlock consists of a sequence counter and a spinlock_t which is used to
serialize the writers. spinlock_t is substituted by a "sleeping" spinlock
on PREEMPT_RT enabled kernels which breaks the usage in the timekeeping
code as the writers are executed in hard interrupt and therefore
non-preemptible context even on PREEMPT_RT.

The spinlock in seqlock cannot be unconditionally replaced by a
raw_spinlock_t as many seqlock users have nesting spinlock sections or
other code which is not suitable to run in truly atomic context on RT.

Instead of providing a raw_seqlock API for a single use case, open code the
seqlock for the jiffies use case and implement it with a raw_spinlock_t and
a sequence counter.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20200321113242.120587764@linutronix.de
2020-03-21 16:00:23 +01:00
Wen Yang
4cbbc3a0ee timekeeping: Prevent 32bit truncation in scale64_check_overflow()
While unlikely the divisor in scale64_check_overflow() could be >= 32bit in
scale64_check_overflow(). do_div() truncates the divisor to 32bit at least
on 32bit platforms.

Use div64_u64() instead to avoid the truncation to 32-bit.

[ tglx: Massaged changelog ]

Signed-off-by: Wen Yang <wenyang@linux.alibaba.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lkml.kernel.org/r/20200120100523.45656-1-wenyang@linux.alibaba.com
2020-03-04 10:17:51 +01:00
Thomas Gleixner
b99328a60a timekeeping/vsyscall: Prevent math overflow in BOOTTIME update
The VDSO update for CLOCK_BOOTTIME has a overflow issue as it shifts the
nanoseconds based boot time offset left by the clocksource shift. That
overflows once the boot time offset becomes large enough. As a consequence
CLOCK_BOOTTIME in the VDSO becomes a random number causing applications to
misbehave.

Fix it by storing a timespec64 representation of the offset when boot time
is adjusted and add that to the MONOTONIC base time value in the vdso data
page. Using the timespec64 representation avoids a 64bit division in the
update code.

Fixes: 44f57d788e ("timekeeping: Provide a generic update_vsyscall() implementation")
Reported-by: Chris Clayton <chris2553@googlemail.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Chris Clayton <chris2553@googlemail.com>
Tested-by: Vincenzo Frascino <vincenzo.frascino@arm.com>
Link: https://lkml.kernel.org/r/alpine.DEB.2.21.1908221257580.1983@nanos.tec.linutronix.de
2019-08-23 02:12:11 +02:00
Jason A. Donenfeld
0354c1a3cd timekeeping: Use proper ktime_add when adding nsecs in coarse offset
While this doesn't actually amount to a real difference, since the macro
evaluates to the same thing, every place else operates on ktime_t using
these functions, so let's not break the pattern.

Fixes: e3ff9c3678 ("timekeeping: Repair ktime_get_coarse*() granularity")
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Arnd Bergmann <arnd@arndb.de>
Link: https://lkml.kernel.org/r/20190621203249.3909-1-Jason@zx2c4.com
2019-06-22 12:11:27 +02:00
Thomas Gleixner
e3ff9c3678 timekeeping: Repair ktime_get_coarse*() granularity
Jason reported that the coarse ktime based time getters advance only once
per second and not once per tick as advertised.

The code reads only the monotonic base time, which advances once per
second. The nanoseconds are accumulated on every tick in xtime_nsec up to
a second and the regular time getters take this nanoseconds offset into
account, but the ktime_get_coarse*() implementation fails to do so.

Add the accumulated xtime_nsec value to the monotonic base time to get the
proper per tick advancing coarse tinme.

Fixes: b9ff604cff ("timekeeping: Add ktime_get_coarse_with_offset")
Reported-by: Jason A. Donenfeld <Jason@zx2c4.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Jason A. Donenfeld <Jason@zx2c4.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Clemens Ladisch <clemens@ladisch.de>
Cc: Sultan Alsawaf <sultan@kerneltoast.com>
Cc: Waiman Long <longman@redhat.com>
Cc: stable@vger.kernel.org
Link: https://lkml.kernel.org/r/alpine.DEB.2.21.1906132136280.1791@nanos.tec.linutronix.de
2019-06-14 11:51:44 +02:00
Linus Torvalds
02aff8db64 audit/stable-5.2 PR 20190507
-----BEGIN PGP SIGNATURE-----
 
 iQJIBAABCAAyFiEES0KozwfymdVUl37v6iDy2pc3iXMFAlzRrzoUHHBhdWxAcGF1
 bC1tb29yZS5jb20ACgkQ6iDy2pc3iXNc7hAApgsi+3Jf9i29mgrKdrTciZ35TegK
 C8pTlOIndpBcmdwDakR50/PgfMHdHll8M9TReVNEjbe0S+Ww5GTE7eWtL3YqoPC2
 MuXEqcriz6UNi5Xma6vCZrDznWLXkXnzMDoDoYGDSoKuUYxef0fuqxDBnERM60Ht
 s52+0XvR5ZseBw7I1KIv/ix2fXuCGq6eCdqassm0rvLPQ7bq6nWzFAlNXOLud303
 DjIWu6Op2EL0+fJSmG+9Z76zFjyEbhMIhw5OPDeH4eO3pxX29AIv0m0JlI7ZXxfc
 /VVC3r5G4WrsWxwKMstOokbmsQxZ5pB3ZaceYpco7U+9N2e3SlpsNM9TV+Y/0ac/
 ynhYa//GK195LpMXx1BmWmLpjBHNgL8MvQkVTIpDia0GT+5sX7+haDxNLGYbocmw
 A/mR+KM2jAU3QzNseGh6c659j3K4tbMIFMNxt7pUBxVPLafcccNngFGTpzCwu5GU
 b7y4d21g6g/3Irj14NYU/qS8dTjW0rYrCMDquTpxmMfZ2xYuSvQmnBw91NQzVBp2
 98L2/fsUG3yOa5MApgv+ryJySsIM+SW+7leKS5tjy/IJINzyPEZ85l3o8ck8X4eT
 nohpKc/ELmeyi3omFYq18ecvFf2YRS5jRnz89i9q65/3ESgGiC0wyGOhNTvjvsyv
 k4jT0slIK614aGk=
 =p8Fp
 -----END PGP SIGNATURE-----

Merge tag 'audit-pr-20190507' of git://git.kernel.org/pub/scm/linux/kernel/git/pcmoore/audit

Pull audit updates from Paul Moore:
 "We've got a reasonably broad set of audit patches for the v5.2 merge
  window, the highlights are below:

   - The biggest change, and the source of all the arch/* changes, is
     the patchset from Dmitry to help enable some of the work he is
     doing around PTRACE_GET_SYSCALL_INFO.

     To be honest, including this in the audit tree is a bit of a
     stretch, but it does help move audit a little further along towards
     proper syscall auditing for all arches, and everyone else seemed to
     agree that audit was a "good" spot for this to land (or maybe they
     just didn't want to merge it? dunno.).

   - We can now audit time/NTP adjustments.

   - We continue the work to connect associated audit records into a
     single event"

* tag 'audit-pr-20190507' of git://git.kernel.org/pub/scm/linux/kernel/git/pcmoore/audit: (21 commits)
  audit: fix a memory leak bug
  ntp: Audit NTP parameters adjustment
  timekeeping: Audit clock adjustments
  audit: purge unnecessary list_empty calls
  audit: link integrity evm_write_xattrs record to syscall event
  syscall_get_arch: add "struct task_struct *" argument
  unicore32: define syscall_get_arch()
  Move EM_UNICORE to uapi/linux/elf-em.h
  nios2: define syscall_get_arch()
  nds32: define syscall_get_arch()
  Move EM_NDS32 to uapi/linux/elf-em.h
  m68k: define syscall_get_arch()
  hexagon: define syscall_get_arch()
  Move EM_HEXAGON to uapi/linux/elf-em.h
  h8300: define syscall_get_arch()
  c6x: define syscall_get_arch()
  arc: define syscall_get_arch()
  Move EM_ARCOMPACT and EM_ARCV2 to uapi/linux/elf-em.h
  audit: Make audit_log_cap and audit_copy_inode static
  audit: connect LOGIN record to its syscall record
  ...
2019-05-07 19:06:04 -07:00