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Author SHA1 Message Date
Thomas Gleixner
f944ffcbc2 watchdog/perf: properly initialize the turbo mode timestamp and rearm counter 
For systems on which the performance counter can expire early due to turbo
modes the watchdog handler has a safety net in place which validates that
since the last watchdog event there has at least 4/5th of the watchdog
period elapsed.

This works reliably only after the first watchdog event because the per
CPU variable which holds the timestamp of the last event is never
initialized.

So a first spurious event will validate against a timestamp of 0 which
results in a delta which is likely to be way over the 4/5 threshold of the
period.  As this might happen before the first watchdog hrtimer event
increments the watchdog counter, this can lead to false positives.

Fix this by initializing the timestamp before enabling the hardware event.
Reset the rearm counter as well, as that might be non zero after the
watchdog was disabled and reenabled.

Link: https://lkml.kernel.org/r/87frsfu15a.ffs@tglx
Fixes: 7edaeb6841 ("kernel/watchdog: Prevent false positives with turbo modes")
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Arjan van de Ven <arjan@linux.intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
 2024-07-17 21:11:34 -07:00
Andrew Morton
8fcb916cac kernel/watchdog_perf.c: tidy up kerneldoc 
It is unconventional to have a blank line between name-of-function and
description-of-args.

Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Song Liu <song@kernel.org>
Cc: "Matthew Wilcox (Oracle)" <willy@infradead.org>
Cc: Ryusuke Konishi <konishi.ryusuke@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
 2024-05-08 08:41:29 -07:00
Song Liu
393fb313a2 watchdog: allow nmi watchdog to use raw perf event 
NMI watchdog permanently consumes one hardware counters per CPU on the
system.  For systems that use many hardware counters, this causes more
aggressive time multiplexing of perf events.

OTOH, some CPUs (mostly Intel) support "ref-cycles" event, which is rarely
used.  Add kernel cmdline arg nmi_watchdog=rNNN to configure the watchdog
to use raw event.  For example, on Intel CPUs, we can use "r300" to
configure the watchdog to use ref-cycles event.

If the raw event does not work, fall back to use "cycles".

[akpm@linux-foundation.org: fix kerneldoc]
Link: https://lkml.kernel.org/r/20240430060236.1878002-2-song@kernel.org
Signed-off-by: Song Liu <song@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: "Matthew Wilcox (Oracle)" <willy@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
 2024-05-08 08:41:29 -07:00
Douglas Anderson
b17aa95933 watchdog/perf: add a weak function for an arch to detect if perf can use NMIs 
On arm64, NMI support needs to be detected at runtime.  Add a weak
function to the perf hardlockup detector so that an architecture can
implement it to detect whether NMIs are available.

Link: https://lkml.kernel.org/r/20230519101840.v5.15.Ic55cb6f90ef5967d8aaa2b503a4e67c753f64d3a@changeid
Signed-off-by: Douglas Anderson <dianders@chromium.org>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Chen-Yu Tsai <wens@csie.org>
Cc: Christophe Leroy <christophe.leroy@csgroup.eu>
Cc: Colin Cross <ccross@android.com>
Cc: Daniel Thompson <daniel.thompson@linaro.org>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Guenter Roeck <groeck@chromium.org>
Cc: Ian Rogers <irogers@google.com>
Cc: Lecopzer Chen <lecopzer.chen@mediatek.com>
Cc: Marc Zyngier <maz@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Masayoshi Mizuma <msys.mizuma@gmail.com>
Cc: Matthias Kaehlcke <mka@chromium.org>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: Petr Mladek <pmladek@suse.com>
Cc: Pingfan Liu <kernelfans@gmail.com>
Cc: Randy Dunlap <rdunlap@infradead.org>
Cc: "Ravi V. Shankar" <ravi.v.shankar@intel.com>
Cc: Ricardo Neri <ricardo.neri@intel.com>
Cc: Stephane Eranian <eranian@google.com>
Cc: Stephen Boyd <swboyd@chromium.org>
Cc: Sumit Garg <sumit.garg@linaro.org>
Cc: Tzung-Bi Shih <tzungbi@chromium.org>
Cc: Will Deacon <will@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
 2023-06-09 17:44:21 -07:00
Douglas Anderson
d9b3629ade watchdog/hardlockup: have the perf hardlockup use __weak functions more cleanly 
The fact that there watchdog_hardlockup_enable(),
watchdog_hardlockup_disable(), and watchdog_hardlockup_probe() are
declared __weak means that the configured hardlockup detector can define
non-weak versions of those functions if it needs to.  Instead of doing
this, the perf hardlockup detector hooked itself into the default __weak
implementation, which was a bit awkward.  Clean this up.

From comments, it looks as if the original design was done because the
__weak function were expected to implemented by the architecture and not
by the configured hardlockup detector.  This got awkward when we tried to
add the buddy lockup detector which was not arch-specific but wanted to
hook into those same functions.

This is not expected to have any functional impact.

Link: https://lkml.kernel.org/r/20230519101840.v5.13.I847d9ec852449350997ba00401d2462a9cb4302b@changeid
Signed-off-by: Douglas Anderson <dianders@chromium.org>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Chen-Yu Tsai <wens@csie.org>
Cc: Christophe Leroy <christophe.leroy@csgroup.eu>
Cc: Colin Cross <ccross@android.com>
Cc: Daniel Thompson <daniel.thompson@linaro.org>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Guenter Roeck <groeck@chromium.org>
Cc: Ian Rogers <irogers@google.com>
Cc: Lecopzer Chen <lecopzer.chen@mediatek.com>
Cc: Marc Zyngier <maz@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Masayoshi Mizuma <msys.mizuma@gmail.com>
Cc: Matthias Kaehlcke <mka@chromium.org>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: Pingfan Liu <kernelfans@gmail.com>
Cc: Randy Dunlap <rdunlap@infradead.org>
Cc: "Ravi V. Shankar" <ravi.v.shankar@intel.com>
Cc: Ricardo Neri <ricardo.neri@intel.com>
Cc: Stephane Eranian <eranian@google.com>
Cc: Stephen Boyd <swboyd@chromium.org>
Cc: Sumit Garg <sumit.garg@linaro.org>
Cc: Tzung-Bi Shih <tzungbi@chromium.org>
Cc: Will Deacon <will@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
 2023-06-09 17:44:21 -07:00
Douglas Anderson
df95d3085c watchdog/hardlockup: rename some "NMI watchdog" constants/function 
Do a search and replace of:
- NMI_WATCHDOG_ENABLED => WATCHDOG_HARDLOCKUP_ENABLED
- SOFT_WATCHDOG_ENABLED => WATCHDOG_SOFTOCKUP_ENABLED
- watchdog_nmi_ => watchdog_hardlockup_
- nmi_watchdog_available => watchdog_hardlockup_available
- nmi_watchdog_user_enabled => watchdog_hardlockup_user_enabled
- soft_watchdog_user_enabled => watchdog_softlockup_user_enabled
- NMI_WATCHDOG_DEFAULT => WATCHDOG_HARDLOCKUP_DEFAULT

Then update a few comments near where names were changed.

This is specifically to make it less confusing when we want to introduce
the buddy hardlockup detector, which isn't using NMIs.  As part of this,
we sanitized a few names for consistency.

[trix@redhat.com: make variables static]
  Link: https://lkml.kernel.org/r/20230525162822.1.I0fb41d138d158c9230573eaa37dc56afa2fb14ee@changeid
Link: https://lkml.kernel.org/r/20230519101840.v5.12.I91f7277bab4bf8c0cb238732ed92e7ce7bbd71a6@changeid
Signed-off-by: Douglas Anderson <dianders@chromium.org>
Signed-off-by: Tom Rix <trix@redhat.com>
Reviewed-by: Tom Rix <trix@redhat.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Chen-Yu Tsai <wens@csie.org>
Cc: Christophe Leroy <christophe.leroy@csgroup.eu>
Cc: Colin Cross <ccross@android.com>
Cc: Daniel Thompson <daniel.thompson@linaro.org>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Guenter Roeck <groeck@chromium.org>
Cc: Ian Rogers <irogers@google.com>
Cc: Lecopzer Chen <lecopzer.chen@mediatek.com>
Cc: Marc Zyngier <maz@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Masayoshi Mizuma <msys.mizuma@gmail.com>
Cc: Matthias Kaehlcke <mka@chromium.org>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: Petr Mladek <pmladek@suse.com>
Cc: Pingfan Liu <kernelfans@gmail.com>
Cc: Randy Dunlap <rdunlap@infradead.org>
Cc: "Ravi V. Shankar" <ravi.v.shankar@intel.com>
Cc: Ricardo Neri <ricardo.neri@intel.com>
Cc: Stephane Eranian <eranian@google.com>
Cc: Stephen Boyd <swboyd@chromium.org>
Cc: Sumit Garg <sumit.garg@linaro.org>
Cc: Tzung-Bi Shih <tzungbi@chromium.org>
Cc: Will Deacon <will@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
 2023-06-09 17:44:20 -07:00
Douglas Anderson
ed92e1ef52 watchdog/hardlockup: move perf hardlockup watchdog petting to watchdog.c 
In preparation for the buddy hardlockup detector, which wants the same
petting logic as the current perf hardlockup detector, move the code to
watchdog.c.  While doing this, rename the global variable to match others
nearby.  As part of this change we have to change the code to account for
the fact that the CPU we're running on might be different than the one
we're checking.

Currently the code in watchdog.c is guarded by
CONFIG_HARDLOCKUP_DETECTOR_PERF, which makes this change seem silly. 
However, a future patch will change this.

Link: https://lkml.kernel.org/r/20230519101840.v5.11.I00dfd6386ee00da25bf26d140559a41339b53e57@changeid
Signed-off-by: Douglas Anderson <dianders@chromium.org>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Chen-Yu Tsai <wens@csie.org>
Cc: Christophe Leroy <christophe.leroy@csgroup.eu>
Cc: Colin Cross <ccross@android.com>
Cc: Daniel Thompson <daniel.thompson@linaro.org>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Guenter Roeck <groeck@chromium.org>
Cc: Ian Rogers <irogers@google.com>
Cc: Lecopzer Chen <lecopzer.chen@mediatek.com>
Cc: Marc Zyngier <maz@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Masayoshi Mizuma <msys.mizuma@gmail.com>
Cc: Matthias Kaehlcke <mka@chromium.org>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: Petr Mladek <pmladek@suse.com>
Cc: Pingfan Liu <kernelfans@gmail.com>
Cc: Randy Dunlap <rdunlap@infradead.org>
Cc: "Ravi V. Shankar" <ravi.v.shankar@intel.com>
Cc: Ricardo Neri <ricardo.neri@intel.com>
Cc: Stephane Eranian <eranian@google.com>
Cc: Stephen Boyd <swboyd@chromium.org>
Cc: Sumit Garg <sumit.garg@linaro.org>
Cc: Tzung-Bi Shih <tzungbi@chromium.org>
Cc: Will Deacon <will@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
 2023-06-09 17:44:20 -07:00
Douglas Anderson
77c12fc959 watchdog/hardlockup: add a "cpu" param to watchdog_hardlockup_check() 
In preparation for the buddy hardlockup detector where the CPU checking
for lockup might not be the currently running CPU, add a "cpu" parameter
to watchdog_hardlockup_check().

As part of this change, make hrtimer_interrupts an atomic_t since now the
CPU incrementing the value and the CPU reading the value might be
different.  Technially this could also be done with just READ_ONCE and
WRITE_ONCE, but atomic_t feels a little cleaner in this case.

While hrtimer_interrupts is made atomic_t, we change
hrtimer_interrupts_saved from "unsigned long" to "int".  The "int" is
needed to match the data type backing atomic_t for hrtimer_interrupts. 
Even if this changes us from 64-bits to 32-bits (which I don't think is
true for most compilers), it doesn't really matter.  All we ever do is
increment it every few seconds and compare it to an old value so 32-bits
is fine (even 16-bits would be).  The "signed" vs "unsigned" also doesn't
matter for simple equality comparisons.

hrtimer_interrupts_saved is _not_ switched to atomic_t nor even accessed
with READ_ONCE / WRITE_ONCE.  The hrtimer_interrupts_saved is always
consistently accessed with the same CPU.  NOTE: with the upcoming "buddy"
detector there is one special case.  When a CPU goes offline/online then
we can change which CPU is the one to consistently access a given instance
of hrtimer_interrupts_saved.  We still can't end up with a partially
updated hrtimer_interrupts_saved, however, because we end up petting all
affected CPUs to make sure the new and old CPU can't end up somehow
read/write hrtimer_interrupts_saved at the same time.

Link: https://lkml.kernel.org/r/20230519101840.v5.10.I3a7d4dd8c23ac30ee0b607d77feb6646b64825c0@changeid
Signed-off-by: Douglas Anderson <dianders@chromium.org>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Chen-Yu Tsai <wens@csie.org>
Cc: Christophe Leroy <christophe.leroy@csgroup.eu>
Cc: Colin Cross <ccross@android.com>
Cc: Daniel Thompson <daniel.thompson@linaro.org>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Guenter Roeck <groeck@chromium.org>
Cc: Ian Rogers <irogers@google.com>
Cc: Lecopzer Chen <lecopzer.chen@mediatek.com>
Cc: Marc Zyngier <maz@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Masayoshi Mizuma <msys.mizuma@gmail.com>
Cc: Matthias Kaehlcke <mka@chromium.org>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: Petr Mladek <pmladek@suse.com>
Cc: Pingfan Liu <kernelfans@gmail.com>
Cc: Randy Dunlap <rdunlap@infradead.org>
Cc: "Ravi V. Shankar" <ravi.v.shankar@intel.com>
Cc: Ricardo Neri <ricardo.neri@intel.com>
Cc: Stephane Eranian <eranian@google.com>
Cc: Stephen Boyd <swboyd@chromium.org>
Cc: Sumit Garg <sumit.garg@linaro.org>
Cc: Tzung-Bi Shih <tzungbi@chromium.org>
Cc: Will Deacon <will@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
 2023-06-09 17:44:20 -07:00
Douglas Anderson
81972551df watchdog/hardlockup: move perf hardlockup checking/panic to common watchdog.c 
The perf hardlockup detector works by looking at interrupt counts and
seeing if they change from run to run.  The interrupt counts are managed
by the common watchdog code via its watchdog_timer_fn().

Currently the API between the perf detector and the common code is a
function: is_hardlockup().  When the hard lockup detector sees that
function return true then it handles printing out debug info and inducing
a panic if necessary.

Let's change the API a little bit in preparation for the buddy hardlockup
detector.  The buddy hardlockup detector wants to print nearly the same
debug info and have nearly the same panic behavior.  That means we want to
move all that code to the common file.  For now, the code in the common
file will only be there if the perf hardlockup detector is enabled, but
eventually it will be selected by a common config.

Right now, this _just_ moves the code from the perf detector file to the
common file and changes the names.  It doesn't make the changes that the
buddy hardlockup detector will need and doesn't do any style cleanups.  A
future patch will do cleanup to make it more obvious what changed.

With the above, we no longer have any callers of is_hardlockup() outside
of the "watchdog.c" file, so we can remove it from the header, make it
static, and move it to the same "#ifdef" block as our new
watchdog_hardlockup_check().  While doing this, it can be noted that even
if no hardlockup detectors were configured the existing code used to still
have the code for counting/checking "hrtimer_interrupts" even if the perf
hardlockup detector wasn't configured.  We didn't need to do that, so move
all the "hrtimer_interrupts" counting to only be there if the perf
hardlockup detector is configured as well.

This change is expected to be a no-op.

Link: https://lkml.kernel.org/r/20230519101840.v5.8.Id4133d3183e798122dc3b6205e7852601f289071@changeid
Signed-off-by: Douglas Anderson <dianders@chromium.org>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Chen-Yu Tsai <wens@csie.org>
Cc: Christophe Leroy <christophe.leroy@csgroup.eu>
Cc: Colin Cross <ccross@android.com>
Cc: Daniel Thompson <daniel.thompson@linaro.org>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Guenter Roeck <groeck@chromium.org>
Cc: Ian Rogers <irogers@google.com>
Cc: Lecopzer Chen <lecopzer.chen@mediatek.com>
Cc: Marc Zyngier <maz@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Masayoshi Mizuma <msys.mizuma@gmail.com>
Cc: Matthias Kaehlcke <mka@chromium.org>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: Pingfan Liu <kernelfans@gmail.com>
Cc: Randy Dunlap <rdunlap@infradead.org>
Cc: "Ravi V. Shankar" <ravi.v.shankar@intel.com>
Cc: Ricardo Neri <ricardo.neri@intel.com>
Cc: Stephane Eranian <eranian@google.com>
Cc: Stephen Boyd <swboyd@chromium.org>
Cc: Sumit Garg <sumit.garg@linaro.org>
Cc: Tzung-Bi Shih <tzungbi@chromium.org>
Cc: Will Deacon <will@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
 2023-06-09 17:44:19 -07:00
Douglas Anderson
6ea0d04211 watchdog/perf: rename watchdog_hld.c to watchdog_perf.c 
The code currently in "watchdog_hld.c" is for detecting hardlockups using
perf, as evidenced by the line in the Makefile that only compiles this
file if CONFIG_HARDLOCKUP_DETECTOR_PERF is defined.  Rename the file to
prepare for the buddy hardlockup detector, which doesn't use perf.

It could be argued that the new name makes it less obvious that this is a
hardlockup detector.  While true, it's not hard to remember that the
"perf" detector is always a hardlockup detector and it's nice not to have
names that are too convoluted.

Link: https://lkml.kernel.org/r/20230519101840.v5.7.Ice803cb078d0e15fb2cbf49132f096ee2bd4199d@changeid
Signed-off-by: Douglas Anderson <dianders@chromium.org>
Acked-by: Nicholas Piggin <npiggin@gmail.com>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Chen-Yu Tsai <wens@csie.org>
Cc: Christophe Leroy <christophe.leroy@csgroup.eu>
Cc: Colin Cross <ccross@android.com>
Cc: Daniel Thompson <daniel.thompson@linaro.org>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Guenter Roeck <groeck@chromium.org>
Cc: Ian Rogers <irogers@google.com>
Cc: Lecopzer Chen <lecopzer.chen@mediatek.com>
Cc: Marc Zyngier <maz@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Masayoshi Mizuma <msys.mizuma@gmail.com>
Cc: Matthias Kaehlcke <mka@chromium.org>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Pingfan Liu <kernelfans@gmail.com>
Cc: Randy Dunlap <rdunlap@infradead.org>
Cc: "Ravi V. Shankar" <ravi.v.shankar@intel.com>
Cc: Ricardo Neri <ricardo.neri@intel.com>
Cc: Stephane Eranian <eranian@google.com>
Cc: Stephen Boyd <swboyd@chromium.org>
Cc: Sumit Garg <sumit.garg@linaro.org>
Cc: Tzung-Bi Shih <tzungbi@chromium.org>
Cc: Will Deacon <will@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
 2023-06-09 17:44:19 -07:00