forked from Minki/linux
Merge branches 'cbnum.2013.06.10a', 'doc.2013.06.10a', 'fixes.2013.06.10a', 'srcu.2013.06.10a' and 'tiny.2013.06.10a' into HEAD
cbnum.2013.06.10a: Apply simplifications stemming from the new callback numbering. doc.2013.06.10a: Documentation updates. fixes.2013.06.10a: Miscellaneous fixes. srcu.2013.06.10a: Updates to SRCU. tiny.2013.06.10a: Eliminate TINY_PREEMPT_RCU.
This commit is contained in:
Paul E. McKenney
commit
be77f87c00
@ -354,12 +354,6 @@ over a rather long period of time, but improvements are always welcome!
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using RCU rather than SRCU, because RCU is almost always faster
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and easier to use than is SRCU.
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If you need to enter your read-side critical section in a
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hardirq or exception handler, and then exit that same read-side
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critical section in the task that was interrupted, then you need
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to srcu_read_lock_raw() and srcu_read_unlock_raw(), which avoid
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the lockdep checking that would otherwise this practice illegal.
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Also unlike other forms of RCU, explicit initialization
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and cleanup is required via init_srcu_struct() and
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cleanup_srcu_struct(). These are passed a "struct srcu_struct"
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@ -182,12 +182,6 @@ torture_type The type of RCU to test, with string values as follows:
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"srcu_expedited": srcu_read_lock(), srcu_read_unlock() and
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synchronize_srcu_expedited().
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"srcu_raw": srcu_read_lock_raw(), srcu_read_unlock_raw(),
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and call_srcu().
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"srcu_raw_sync": srcu_read_lock_raw(), srcu_read_unlock_raw(),
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and synchronize_srcu().
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"sched": preempt_disable(), preempt_enable(), and
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call_rcu_sched().
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@ -530,113 +530,21 @@ o "nos" counts the number of times we balked for other
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reasons, e.g., the grace period ended first.
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CONFIG_TINY_RCU and CONFIG_TINY_PREEMPT_RCU debugfs Files and Formats
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CONFIG_TINY_RCU debugfs Files and Formats
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These implementations of RCU provides a single debugfs file under the
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top-level directory RCU, namely rcu/rcudata, which displays fields in
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rcu_bh_ctrlblk, rcu_sched_ctrlblk and, for CONFIG_TINY_PREEMPT_RCU,
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rcu_preempt_ctrlblk.
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rcu_bh_ctrlblk and rcu_sched_ctrlblk.
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The output of "cat rcu/rcudata" is as follows:
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rcu_preempt: qlen=24 gp=1097669 g197/p197/c197 tasks=...
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ttb=. btg=no ntb=184 neb=0 nnb=183 j=01f7 bt=0274
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normal balk: nt=1097669 gt=0 bt=371 b=0 ny=25073378 nos=0
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exp balk: bt=0 nos=0
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rcu_sched: qlen: 0
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rcu_bh: qlen: 0
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This is split into rcu_preempt, rcu_sched, and rcu_bh sections, with the
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rcu_preempt section appearing only in CONFIG_TINY_PREEMPT_RCU builds.
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The last three lines of the rcu_preempt section appear only in
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CONFIG_RCU_BOOST kernel builds. The fields are as follows:
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This is split into rcu_sched and rcu_bh sections. The field is as
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follows:
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o "qlen" is the number of RCU callbacks currently waiting either
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for an RCU grace period or waiting to be invoked. This is the
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only field present for rcu_sched and rcu_bh, due to the
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short-circuiting of grace period in those two cases.
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o "gp" is the number of grace periods that have completed.
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o "g197/p197/c197" displays the grace-period state, with the
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"g" number being the number of grace periods that have started
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(mod 256), the "p" number being the number of grace periods
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that the CPU has responded to (also mod 256), and the "c"
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number being the number of grace periods that have completed
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(once again mode 256).
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Why have both "gp" and "g"? Because the data flowing into
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"gp" is only present in a CONFIG_RCU_TRACE kernel.
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o "tasks" is a set of bits. The first bit is "T" if there are
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currently tasks that have recently blocked within an RCU
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read-side critical section, the second bit is "N" if any of the
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aforementioned tasks are blocking the current RCU grace period,
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and the third bit is "E" if any of the aforementioned tasks are
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blocking the current expedited grace period. Each bit is "."
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if the corresponding condition does not hold.
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o "ttb" is a single bit. It is "B" if any of the blocked tasks
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need to be priority boosted and "." otherwise.
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o "btg" indicates whether boosting has been carried out during
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the current grace period, with "exp" indicating that boosting
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is in progress for an expedited grace period, "no" indicating
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that boosting has not yet started for a normal grace period,
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"begun" indicating that boosting has bebug for a normal grace
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period, and "done" indicating that boosting has completed for
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a normal grace period.
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o "ntb" is the total number of tasks subjected to RCU priority boosting
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periods since boot.
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o "neb" is the number of expedited grace periods that have had
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to resort to RCU priority boosting since boot.
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o "nnb" is the number of normal grace periods that have had
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to resort to RCU priority boosting since boot.
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o "j" is the low-order 16 bits of the jiffies counter in hexadecimal.
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o "bt" is the low-order 16 bits of the value that the jiffies counter
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will have at the next time that boosting is scheduled to begin.
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o In the line beginning with "normal balk", the fields are as follows:
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o "nt" is the number of times that the system balked from
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boosting because there were no blocked tasks to boost.
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Note that the system will balk from boosting even if the
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grace period is overdue when the currently running task
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is looping within an RCU read-side critical section.
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There is no point in boosting in this case, because
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boosting a running task won't make it run any faster.
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o "gt" is the number of times that the system balked
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from boosting because, although there were blocked tasks,
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none of them were preventing the current grace period
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from completing.
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o "bt" is the number of times that the system balked
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from boosting because boosting was already in progress.
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o "b" is the number of times that the system balked from
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boosting because boosting had already completed for
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the grace period in question.
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o "ny" is the number of times that the system balked from
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boosting because it was not yet time to start boosting
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the grace period in question.
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o "nos" is the number of times that the system balked from
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boosting for inexplicable ("not otherwise specified")
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reasons. This can actually happen due to races involving
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increments of the jiffies counter.
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o In the line beginning with "exp balk", the fields are as follows:
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o "bt" is the number of times that the system balked from
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boosting because there were no blocked tasks to boost.
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o "nos" is the number of times that the system balked from
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boosting for inexplicable ("not otherwise specified")
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reasons.
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@ -842,9 +842,7 @@ SRCU: Critical sections Grace period Barrier
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srcu_read_lock synchronize_srcu srcu_barrier
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srcu_read_unlock call_srcu
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srcu_read_lock_raw synchronize_srcu_expedited
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srcu_read_unlock_raw
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srcu_dereference
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srcu_dereference synchronize_srcu_expedited
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SRCU: Initialization/cleanup
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init_srcu_struct
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@ -865,38 +863,32 @@ list can be helpful:
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a. Will readers need to block? If so, you need SRCU.
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b. Is it necessary to start a read-side critical section in a
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hardirq handler or exception handler, and then to complete
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this read-side critical section in the task that was
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interrupted? If so, you need SRCU's srcu_read_lock_raw() and
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srcu_read_unlock_raw() primitives.
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c. What about the -rt patchset? If readers would need to block
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b. What about the -rt patchset? If readers would need to block
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in an non-rt kernel, you need SRCU. If readers would block
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in a -rt kernel, but not in a non-rt kernel, SRCU is not
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necessary.
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d. Do you need to treat NMI handlers, hardirq handlers,
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c. Do you need to treat NMI handlers, hardirq handlers,
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and code segments with preemption disabled (whether
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via preempt_disable(), local_irq_save(), local_bh_disable(),
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or some other mechanism) as if they were explicit RCU readers?
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If so, RCU-sched is the only choice that will work for you.
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e. Do you need RCU grace periods to complete even in the face
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d. Do you need RCU grace periods to complete even in the face
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of softirq monopolization of one or more of the CPUs? For
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example, is your code subject to network-based denial-of-service
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attacks? If so, you need RCU-bh.
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f. Is your workload too update-intensive for normal use of
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e. Is your workload too update-intensive for normal use of
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RCU, but inappropriate for other synchronization mechanisms?
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If so, consider SLAB_DESTROY_BY_RCU. But please be careful!
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g. Do you need read-side critical sections that are respected
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f. Do you need read-side critical sections that are respected
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even though they are in the middle of the idle loop, during
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user-mode execution, or on an offlined CPU? If so, SRCU is the
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only choice that will work for you.
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h. Otherwise, use RCU.
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g. Otherwise, use RCU.
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Of course, this all assumes that you have determined that RCU is in fact
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the right tool for your job.
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@ -157,6 +157,53 @@ RCU_SOFTIRQ: Do at least one of the following:
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calls and by forcing both kernel threads and interrupts
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to execute elsewhere.
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Name: kworker/%u:%d%s (cpu, id, priority)
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Purpose: Execute workqueue requests
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To reduce its OS jitter, do any of the following:
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1. Run your workload at a real-time priority, which will allow
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preempting the kworker daemons.
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2. Do any of the following needed to avoid jitter that your
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application cannot tolerate:
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a. Build your kernel with CONFIG_SLUB=y rather than
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CONFIG_SLAB=y, thus avoiding the slab allocator's periodic
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use of each CPU's workqueues to run its cache_reap()
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function.
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b. Avoid using oprofile, thus avoiding OS jitter from
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wq_sync_buffer().
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c. Limit your CPU frequency so that a CPU-frequency
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governor is not required, possibly enlisting the aid of
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special heatsinks or other cooling technologies. If done
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correctly, and if you CPU architecture permits, you should
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be able to build your kernel with CONFIG_CPU_FREQ=n to
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avoid the CPU-frequency governor periodically running
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on each CPU, including cs_dbs_timer() and od_dbs_timer().
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WARNING: Please check your CPU specifications to
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make sure that this is safe on your particular system.
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d. It is not possible to entirely get rid of OS jitter
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from vmstat_update() on CONFIG_SMP=y systems, but you
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can decrease its frequency by writing a large value to
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/proc/sys/vm/stat_interval. The default value is HZ,
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for an interval of one second. Of course, larger values
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will make your virtual-memory statistics update more
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slowly. Of course, you can also run your workload at
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a real-time priority, thus preempting vmstat_update().
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e. If running on high-end powerpc servers, build with
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CONFIG_PPC_RTAS_DAEMON=n. This prevents the RTAS
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daemon from running on each CPU every second or so.
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(This will require editing Kconfig files and will defeat
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this platform's RAS functionality.) This avoids jitter
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due to the rtas_event_scan() function.
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WARNING: Please check your CPU specifications to
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make sure that this is safe on your particular system.
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f. If running on Cell Processor, build your kernel with
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CBE_CPUFREQ_SPU_GOVERNOR=n to avoid OS jitter from
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spu_gov_work().
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WARNING: Please check your CPU specifications to
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make sure that this is safe on your particular system.
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g. If running on PowerMAC, build your kernel with
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CONFIG_PMAC_RACKMETER=n to disable the CPU-meter,
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avoiding OS jitter from rackmeter_do_timer().
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Name: rcuc/%u
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Purpose: Execute RCU callbacks in CONFIG_RCU_BOOST=y kernels.
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To reduce its OS jitter, do at least one of the following:
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@ -7,21 +7,59 @@ efficiency and reducing OS jitter. Reducing OS jitter is important for
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some types of computationally intensive high-performance computing (HPC)
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applications and for real-time applications.
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There are two main contexts in which the number of scheduling-clock
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interrupts can be reduced compared to the old-school approach of sending
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a scheduling-clock interrupt to all CPUs every jiffy whether they need
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it or not (CONFIG_HZ_PERIODIC=y or CONFIG_NO_HZ=n for older kernels):
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There are three main ways of managing scheduling-clock interrupts
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(also known as "scheduling-clock ticks" or simply "ticks"):
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1. Idle CPUs (CONFIG_NO_HZ_IDLE=y or CONFIG_NO_HZ=y for older kernels).
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1. Never omit scheduling-clock ticks (CONFIG_HZ_PERIODIC=y or
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CONFIG_NO_HZ=n for older kernels). You normally will -not-
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want to choose this option.
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2. CPUs having only one runnable task (CONFIG_NO_HZ_FULL=y).
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2. Omit scheduling-clock ticks on idle CPUs (CONFIG_NO_HZ_IDLE=y or
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CONFIG_NO_HZ=y for older kernels). This is the most common
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approach, and should be the default.
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These two cases are described in the following two sections, followed
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3. Omit scheduling-clock ticks on CPUs that are either idle or that
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have only one runnable task (CONFIG_NO_HZ_FULL=y). Unless you
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are running realtime applications or certain types of HPC
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workloads, you will normally -not- want this option.
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These three cases are described in the following three sections, followed
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by a third section on RCU-specific considerations and a fourth and final
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section listing known issues.
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IDLE CPUs
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NEVER OMIT SCHEDULING-CLOCK TICKS
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Very old versions of Linux from the 1990s and the very early 2000s
|
||||
are incapable of omitting scheduling-clock ticks. It turns out that
|
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there are some situations where this old-school approach is still the
|
||||
right approach, for example, in heavy workloads with lots of tasks
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that use short bursts of CPU, where there are very frequent idle
|
||||
periods, but where these idle periods are also quite short (tens or
|
||||
hundreds of microseconds). For these types of workloads, scheduling
|
||||
clock interrupts will normally be delivered any way because there
|
||||
will frequently be multiple runnable tasks per CPU. In these cases,
|
||||
attempting to turn off the scheduling clock interrupt will have no effect
|
||||
other than increasing the overhead of switching to and from idle and
|
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transitioning between user and kernel execution.
|
||||
|
||||
This mode of operation can be selected using CONFIG_HZ_PERIODIC=y (or
|
||||
CONFIG_NO_HZ=n for older kernels).
|
||||
|
||||
However, if you are instead running a light workload with long idle
|
||||
periods, failing to omit scheduling-clock interrupts will result in
|
||||
excessive power consumption. This is especially bad on battery-powered
|
||||
devices, where it results in extremely short battery lifetimes. If you
|
||||
are running light workloads, you should therefore read the following
|
||||
section.
|
||||
|
||||
In addition, if you are running either a real-time workload or an HPC
|
||||
workload with short iterations, the scheduling-clock interrupts can
|
||||
degrade your applications performance. If this describes your workload,
|
||||
you should read the following two sections.
|
||||
|
||||
|
||||
OMIT SCHEDULING-CLOCK TICKS FOR IDLE CPUs
|
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|
||||
If a CPU is idle, there is little point in sending it a scheduling-clock
|
||||
interrupt. After all, the primary purpose of a scheduling-clock interrupt
|
||||
@ -59,10 +97,12 @@ By default, CONFIG_NO_HZ_IDLE=y kernels boot with "nohz=on", enabling
|
||||
dyntick-idle mode.
|
||||
|
||||
|
||||
CPUs WITH ONLY ONE RUNNABLE TASK
|
||||
OMIT SCHEDULING-CLOCK TICKS FOR CPUs WITH ONLY ONE RUNNABLE TASK
|
||||
|
||||
If a CPU has only one runnable task, there is little point in sending it
|
||||
a scheduling-clock interrupt because there is no other task to switch to.
|
||||
Note that omitting scheduling-clock ticks for CPUs with only one runnable
|
||||
task implies also omitting them for idle CPUs.
|
||||
|
||||
The CONFIG_NO_HZ_FULL=y Kconfig option causes the kernel to avoid
|
||||
sending scheduling-clock interrupts to CPUs with a single runnable task,
|
||||
@ -238,6 +278,11 @@ o Adaptive-ticks does not do anything unless there is only one
|
||||
single runnable SCHED_FIFO task and multiple runnable SCHED_OTHER
|
||||
tasks, even though these interrupts are unnecessary.
|
||||
|
||||
And even when there are multiple runnable tasks on a given CPU,
|
||||
there is little point in interrupting that CPU until the current
|
||||
running task's timeslice expires, which is almost always way
|
||||
longer than the time of the next scheduling-clock interrupt.
|
||||
|
||||
Better handling of these sorts of situations is future work.
|
||||
|
||||
o A reboot is required to reconfigure both adaptive idle and RCU
|
||||
@ -268,6 +313,16 @@ o Unless all CPUs are idle, at least one CPU must keep the
|
||||
scheduling-clock interrupt going in order to support accurate
|
||||
timekeeping.
|
||||
|
||||
o If there are adaptive-ticks CPUs, there will be at least one
|
||||
CPU keeping the scheduling-clock interrupt going, even if all
|
||||
CPUs are otherwise idle.
|
||||
o If there might potentially be some adaptive-ticks CPUs, there
|
||||
will be at least one CPU keeping the scheduling-clock interrupt
|
||||
going, even if all CPUs are otherwise idle.
|
||||
|
||||
Better handling of this situation is ongoing work.
|
||||
|
||||
o Some process-handling operations still require the occasional
|
||||
scheduling-clock tick. These operations include calculating CPU
|
||||
load, maintaining sched average, computing CFS entity vruntime,
|
||||
computing avenrun, and carrying out load balancing. They are
|
||||
currently accommodated by scheduling-clock tick every second
|
||||
or so. On-going work will eliminate the need even for these
|
||||
infrequent scheduling-clock ticks.
|
||||
|
||||
@ -1864,7 +1864,7 @@ static int kvmppc_hv_setup_htab_rma(struct kvm_vcpu *vcpu)
|
||||
|
||||
up_out:
|
||||
up_read(¤t->mm->mmap_sem);
|
||||
goto out;
|
||||
goto out_srcu;
|
||||
}
|
||||
|
||||
int kvmppc_core_init_vm(struct kvm *kvm)
|
||||
|
||||
@ -128,7 +128,7 @@ extern void synchronize_irq(unsigned int irq);
|
||||
# define synchronize_irq(irq) barrier()
|
||||
#endif
|
||||
|
||||
#if defined(CONFIG_TINY_RCU) || defined(CONFIG_TINY_PREEMPT_RCU)
|
||||
#if defined(CONFIG_TINY_RCU)
|
||||
|
||||
static inline void rcu_nmi_enter(void)
|
||||
{
|
||||
|
||||
@ -216,6 +216,7 @@ static inline int rcu_preempt_depth(void)
|
||||
#endif /* #else #ifdef CONFIG_PREEMPT_RCU */
|
||||
|
||||
/* Internal to kernel */
|
||||
extern void rcu_init(void);
|
||||
extern void rcu_sched_qs(int cpu);
|
||||
extern void rcu_bh_qs(int cpu);
|
||||
extern void rcu_check_callbacks(int cpu, int user);
|
||||
@ -239,8 +240,6 @@ static inline void rcu_user_hooks_switch(struct task_struct *prev,
|
||||
struct task_struct *next) { }
|
||||
#endif /* CONFIG_RCU_USER_QS */
|
||||
|
||||
extern void exit_rcu(void);
|
||||
|
||||
/**
|
||||
* RCU_NONIDLE - Indicate idle-loop code that needs RCU readers
|
||||
* @a: Code that RCU needs to pay attention to.
|
||||
@ -277,7 +276,7 @@ void wait_rcu_gp(call_rcu_func_t crf);
|
||||
|
||||
#if defined(CONFIG_TREE_RCU) || defined(CONFIG_TREE_PREEMPT_RCU)
|
||||
#include <linux/rcutree.h>
|
||||
#elif defined(CONFIG_TINY_RCU) || defined(CONFIG_TINY_PREEMPT_RCU)
|
||||
#elif defined(CONFIG_TINY_RCU)
|
||||
#include <linux/rcutiny.h>
|
||||
#else
|
||||
#error "Unknown RCU implementation specified to kernel configuration"
|
||||
|
||||
@ -27,10 +27,6 @@
|
||||
|
||||
#include <linux/cache.h>
|
||||
|
||||
static inline void rcu_init(void)
|
||||
{
|
||||
}
|
||||
|
||||
static inline void rcu_barrier_bh(void)
|
||||
{
|
||||
wait_rcu_gp(call_rcu_bh);
|
||||
@ -41,8 +37,6 @@ static inline void rcu_barrier_sched(void)
|
||||
wait_rcu_gp(call_rcu_sched);
|
||||
}
|
||||
|
||||
#ifdef CONFIG_TINY_RCU
|
||||
|
||||
static inline void synchronize_rcu_expedited(void)
|
||||
{
|
||||
synchronize_sched(); /* Only one CPU, so pretty fast anyway!!! */
|
||||
@ -53,17 +47,6 @@ static inline void rcu_barrier(void)
|
||||
rcu_barrier_sched(); /* Only one CPU, so only one list of callbacks! */
|
||||
}
|
||||
|
||||
#else /* #ifdef CONFIG_TINY_RCU */
|
||||
|
||||
void synchronize_rcu_expedited(void);
|
||||
|
||||
static inline void rcu_barrier(void)
|
||||
{
|
||||
wait_rcu_gp(call_rcu);
|
||||
}
|
||||
|
||||
#endif /* #else #ifdef CONFIG_TINY_RCU */
|
||||
|
||||
static inline void synchronize_rcu_bh(void)
|
||||
{
|
||||
synchronize_sched();
|
||||
@ -85,35 +68,15 @@ static inline void kfree_call_rcu(struct rcu_head *head,
|
||||
call_rcu(head, func);
|
||||
}
|
||||
|
||||
#ifdef CONFIG_TINY_RCU
|
||||
|
||||
static inline void rcu_preempt_note_context_switch(void)
|
||||
{
|
||||
}
|
||||
|
||||
static inline int rcu_needs_cpu(int cpu, unsigned long *delta_jiffies)
|
||||
{
|
||||
*delta_jiffies = ULONG_MAX;
|
||||
return 0;
|
||||
}
|
||||
|
||||
#else /* #ifdef CONFIG_TINY_RCU */
|
||||
|
||||
void rcu_preempt_note_context_switch(void);
|
||||
int rcu_preempt_needs_cpu(void);
|
||||
|
||||
static inline int rcu_needs_cpu(int cpu, unsigned long *delta_jiffies)
|
||||
{
|
||||
*delta_jiffies = ULONG_MAX;
|
||||
return rcu_preempt_needs_cpu();
|
||||
}
|
||||
|
||||
#endif /* #else #ifdef CONFIG_TINY_RCU */
|
||||
|
||||
static inline void rcu_note_context_switch(int cpu)
|
||||
{
|
||||
rcu_sched_qs(cpu);
|
||||
rcu_preempt_note_context_switch();
|
||||
}
|
||||
|
||||
/*
|
||||
@ -156,6 +119,10 @@ static inline void rcu_cpu_stall_reset(void)
|
||||
{
|
||||
}
|
||||
|
||||
static inline void exit_rcu(void)
|
||||
{
|
||||
}
|
||||
|
||||
#ifdef CONFIG_DEBUG_LOCK_ALLOC
|
||||
extern int rcu_scheduler_active __read_mostly;
|
||||
extern void rcu_scheduler_starting(void);
|
||||
|
||||
@ -30,7 +30,6 @@
|
||||
#ifndef __LINUX_RCUTREE_H
|
||||
#define __LINUX_RCUTREE_H
|
||||
|
||||
extern void rcu_init(void);
|
||||
extern void rcu_note_context_switch(int cpu);
|
||||
extern int rcu_needs_cpu(int cpu, unsigned long *delta_jiffies);
|
||||
extern void rcu_cpu_stall_reset(void);
|
||||
@ -86,6 +85,8 @@ extern void rcu_force_quiescent_state(void);
|
||||
extern void rcu_bh_force_quiescent_state(void);
|
||||
extern void rcu_sched_force_quiescent_state(void);
|
||||
|
||||
extern void exit_rcu(void);
|
||||
|
||||
extern void rcu_scheduler_starting(void);
|
||||
extern int rcu_scheduler_active __read_mostly;
|
||||
|
||||
|
||||
@ -237,47 +237,4 @@ static inline void srcu_read_unlock(struct srcu_struct *sp, int idx)
|
||||
__srcu_read_unlock(sp, idx);
|
||||
}
|
||||
|
||||
/**
|
||||
* srcu_read_lock_raw - register a new reader for an SRCU-protected structure.
|
||||
* @sp: srcu_struct in which to register the new reader.
|
||||
*
|
||||
* Enter an SRCU read-side critical section. Similar to srcu_read_lock(),
|
||||
* but avoids the RCU-lockdep checking. This means that it is legal to
|
||||
* use srcu_read_lock_raw() in one context, for example, in an exception
|
||||
* handler, and then have the matching srcu_read_unlock_raw() in another
|
||||
* context, for example in the task that took the exception.
|
||||
*
|
||||
* However, the entire SRCU read-side critical section must reside within a
|
||||
* single task. For example, beware of using srcu_read_lock_raw() in
|
||||
* a device interrupt handler and srcu_read_unlock() in the interrupted
|
||||
* task: This will not work if interrupts are threaded.
|
||||
*/
|
||||
static inline int srcu_read_lock_raw(struct srcu_struct *sp)
|
||||
{
|
||||
unsigned long flags;
|
||||
int ret;
|
||||
|
||||
local_irq_save(flags);
|
||||
ret = __srcu_read_lock(sp);
|
||||
local_irq_restore(flags);
|
||||
return ret;
|
||||
}
|
||||
|
||||
/**
|
||||
* srcu_read_unlock_raw - unregister reader from an SRCU-protected structure.
|
||||
* @sp: srcu_struct in which to unregister the old reader.
|
||||
* @idx: return value from corresponding srcu_read_lock_raw().
|
||||
*
|
||||
* Exit an SRCU read-side critical section without lockdep-RCU checking.
|
||||
* See srcu_read_lock_raw() for more details.
|
||||
*/
|
||||
static inline void srcu_read_unlock_raw(struct srcu_struct *sp, int idx)
|
||||
{
|
||||
unsigned long flags;
|
||||
|
||||
local_irq_save(flags);
|
||||
__srcu_read_unlock(sp, idx);
|
||||
local_irq_restore(flags);
|
||||
}
|
||||
|
||||
#endif
|
||||
|
||||
46
init/Kconfig
46
init/Kconfig
@ -459,18 +459,10 @@ config TINY_RCU
|
||||
is not required. This option greatly reduces the
|
||||
memory footprint of RCU.
|
||||
|
||||
config TINY_PREEMPT_RCU
|
||||
bool "Preemptible UP-only small-memory-footprint RCU"
|
||||
depends on PREEMPT && !SMP
|
||||
help
|
||||
This option selects the RCU implementation that is designed
|
||||
for real-time UP systems. This option greatly reduces the
|
||||
memory footprint of RCU.
|
||||
|
||||
endchoice
|
||||
|
||||
config PREEMPT_RCU
|
||||
def_bool ( TREE_PREEMPT_RCU || TINY_PREEMPT_RCU )
|
||||
def_bool TREE_PREEMPT_RCU
|
||||
help
|
||||
This option enables preemptible-RCU code that is common between
|
||||
the TREE_PREEMPT_RCU and TINY_PREEMPT_RCU implementations.
|
||||
@ -656,7 +648,7 @@ config RCU_BOOST_DELAY
|
||||
Accept the default if unsure.
|
||||
|
||||
config RCU_NOCB_CPU
|
||||
bool "Offload RCU callback processing from boot-selected CPUs (EXPERIMENTAL"
|
||||
bool "Offload RCU callback processing from boot-selected CPUs"
|
||||
depends on TREE_RCU || TREE_PREEMPT_RCU
|
||||
default n
|
||||
help
|
||||
@ -682,9 +674,10 @@ choice
|
||||
prompt "Build-forced no-CBs CPUs"
|
||||
default RCU_NOCB_CPU_NONE
|
||||
help
|
||||
This option allows no-CBs CPUs to be specified at build time.
|
||||
Additional no-CBs CPUs may be specified by the rcu_nocbs=
|
||||
boot parameter.
|
||||
This option allows no-CBs CPUs (whose RCU callbacks are invoked
|
||||
from kthreads rather than from softirq context) to be specified
|
||||
at build time. Additional no-CBs CPUs may be specified by
|
||||
the rcu_nocbs= boot parameter.
|
||||
|
||||
config RCU_NOCB_CPU_NONE
|
||||
bool "No build_forced no-CBs CPUs"
|
||||
@ -692,25 +685,40 @@ config RCU_NOCB_CPU_NONE
|
||||
help
|
||||
This option does not force any of the CPUs to be no-CBs CPUs.
|
||||
Only CPUs designated by the rcu_nocbs= boot parameter will be
|
||||
no-CBs CPUs.
|
||||
no-CBs CPUs, whose RCU callbacks will be invoked by per-CPU
|
||||
kthreads whose names begin with "rcuo". All other CPUs will
|
||||
invoke their own RCU callbacks in softirq context.
|
||||
|
||||
Select this option if you want to choose no-CBs CPUs at
|
||||
boot time, for example, to allow testing of different no-CBs
|
||||
configurations without having to rebuild the kernel each time.
|
||||
|
||||
config RCU_NOCB_CPU_ZERO
|
||||
bool "CPU 0 is a build_forced no-CBs CPU"
|
||||
depends on RCU_NOCB_CPU && !NO_HZ_FULL
|
||||
help
|
||||
This option forces CPU 0 to be a no-CBs CPU. Additional CPUs
|
||||
may be designated as no-CBs CPUs using the rcu_nocbs= boot
|
||||
parameter will be no-CBs CPUs.
|
||||
This option forces CPU 0 to be a no-CBs CPU, so that its RCU
|
||||
callbacks are invoked by a per-CPU kthread whose name begins
|
||||
with "rcuo". Additional CPUs may be designated as no-CBs
|
||||
CPUs using the rcu_nocbs= boot parameter will be no-CBs CPUs.
|
||||
All other CPUs will invoke their own RCU callbacks in softirq
|
||||
context.
|
||||
|
||||
Select this if CPU 0 needs to be a no-CBs CPU for real-time
|
||||
or energy-efficiency reasons.
|
||||
or energy-efficiency reasons, but the real reason it exists
|
||||
is to ensure that randconfig testing covers mixed systems.
|
||||
|
||||
config RCU_NOCB_CPU_ALL
|
||||
bool "All CPUs are build_forced no-CBs CPUs"
|
||||
depends on RCU_NOCB_CPU
|
||||
help
|
||||
This option forces all CPUs to be no-CBs CPUs. The rcu_nocbs=
|
||||
boot parameter will be ignored.
|
||||
boot parameter will be ignored. All CPUs' RCU callbacks will
|
||||
be executed in the context of per-CPU rcuo kthreads created for
|
||||
this purpose. Assuming that the kthreads whose names start with
|
||||
"rcuo" are bound to "housekeeping" CPUs, this reduces OS jitter
|
||||
on the remaining CPUs, but might decrease memory locality during
|
||||
RCU-callback invocation, thus potentially degrading throughput.
|
||||
|
||||
Select this if all CPUs need to be no-CBs CPUs for real-time
|
||||
or energy-efficiency reasons.
|
||||
|
||||
@ -104,31 +104,7 @@ void __rcu_read_unlock(void)
|
||||
}
|
||||
EXPORT_SYMBOL_GPL(__rcu_read_unlock);
|
||||
|
||||
/*
|
||||
* Check for a task exiting while in a preemptible-RCU read-side
|
||||
* critical section, clean up if so. No need to issue warnings,
|
||||
* as debug_check_no_locks_held() already does this if lockdep
|
||||
* is enabled.
|
||||
*/
|
||||
void exit_rcu(void)
|
||||
{
|
||||
struct task_struct *t = current;
|
||||
|
||||
if (likely(list_empty(¤t->rcu_node_entry)))
|
||||
return;
|
||||
t->rcu_read_lock_nesting = 1;
|
||||
barrier();
|
||||
t->rcu_read_unlock_special = RCU_READ_UNLOCK_BLOCKED;
|
||||
__rcu_read_unlock();
|
||||
}
|
||||
|
||||
#else /* #ifdef CONFIG_PREEMPT_RCU */
|
||||
|
||||
void exit_rcu(void)
|
||||
{
|
||||
}
|
||||
|
||||
#endif /* #else #ifdef CONFIG_PREEMPT_RCU */
|
||||
#endif /* #ifdef CONFIG_PREEMPT_RCU */
|
||||
|
||||
#ifdef CONFIG_DEBUG_LOCK_ALLOC
|
||||
static struct lock_class_key rcu_lock_key;
|
||||
@ -145,9 +121,6 @@ static struct lock_class_key rcu_sched_lock_key;
|
||||
struct lockdep_map rcu_sched_lock_map =
|
||||
STATIC_LOCKDEP_MAP_INIT("rcu_read_lock_sched", &rcu_sched_lock_key);
|
||||
EXPORT_SYMBOL_GPL(rcu_sched_lock_map);
|
||||
#endif
|
||||
|
||||
#ifdef CONFIG_DEBUG_LOCK_ALLOC
|
||||
|
||||
int debug_lockdep_rcu_enabled(void)
|
||||
{
|
||||
|
||||
@ -44,7 +44,6 @@
|
||||
|
||||
/* Forward declarations for rcutiny_plugin.h. */
|
||||
struct rcu_ctrlblk;
|
||||
static void invoke_rcu_callbacks(void);
|
||||
static void __rcu_process_callbacks(struct rcu_ctrlblk *rcp);
|
||||
static void rcu_process_callbacks(struct softirq_action *unused);
|
||||
static void __call_rcu(struct rcu_head *head,
|
||||
@ -205,7 +204,7 @@ static int rcu_is_cpu_rrupt_from_idle(void)
|
||||
*/
|
||||
static int rcu_qsctr_help(struct rcu_ctrlblk *rcp)
|
||||
{
|
||||
reset_cpu_stall_ticks(rcp);
|
||||
RCU_TRACE(reset_cpu_stall_ticks(rcp));
|
||||
if (rcp->rcucblist != NULL &&
|
||||
rcp->donetail != rcp->curtail) {
|
||||
rcp->donetail = rcp->curtail;
|
||||
@ -227,7 +226,7 @@ void rcu_sched_qs(int cpu)
|
||||
local_irq_save(flags);
|
||||
if (rcu_qsctr_help(&rcu_sched_ctrlblk) +
|
||||
rcu_qsctr_help(&rcu_bh_ctrlblk))
|
||||
invoke_rcu_callbacks();
|
||||
raise_softirq(RCU_SOFTIRQ);
|
||||
local_irq_restore(flags);
|
||||
}
|
||||
|
||||
@ -240,7 +239,7 @@ void rcu_bh_qs(int cpu)
|
||||
|
||||
local_irq_save(flags);
|
||||
if (rcu_qsctr_help(&rcu_bh_ctrlblk))
|
||||
invoke_rcu_callbacks();
|
||||
raise_softirq(RCU_SOFTIRQ);
|
||||
local_irq_restore(flags);
|
||||
}
|
||||
|
||||
@ -252,12 +251,11 @@ void rcu_bh_qs(int cpu)
|
||||
*/
|
||||
void rcu_check_callbacks(int cpu, int user)
|
||||
{
|
||||
check_cpu_stalls();
|
||||
RCU_TRACE(check_cpu_stalls());
|
||||
if (user || rcu_is_cpu_rrupt_from_idle())
|
||||
rcu_sched_qs(cpu);
|
||||
else if (!in_softirq())
|
||||
rcu_bh_qs(cpu);
|
||||
rcu_preempt_check_callbacks();
|
||||
}
|
||||
|
||||
/*
|
||||
@ -278,7 +276,7 @@ static void __rcu_process_callbacks(struct rcu_ctrlblk *rcp)
|
||||
ACCESS_ONCE(rcp->rcucblist),
|
||||
need_resched(),
|
||||
is_idle_task(current),
|
||||
rcu_is_callbacks_kthread()));
|
||||
false));
|
||||
return;
|
||||
}
|
||||
|
||||
@ -290,7 +288,6 @@ static void __rcu_process_callbacks(struct rcu_ctrlblk *rcp)
|
||||
*rcp->donetail = NULL;
|
||||
if (rcp->curtail == rcp->donetail)
|
||||
rcp->curtail = &rcp->rcucblist;
|
||||
rcu_preempt_remove_callbacks(rcp);
|
||||
rcp->donetail = &rcp->rcucblist;
|
||||
local_irq_restore(flags);
|
||||
|
||||
@ -309,14 +306,13 @@ static void __rcu_process_callbacks(struct rcu_ctrlblk *rcp)
|
||||
RCU_TRACE(rcu_trace_sub_qlen(rcp, cb_count));
|
||||
RCU_TRACE(trace_rcu_batch_end(rcp->name, cb_count, 0, need_resched(),
|
||||
is_idle_task(current),
|
||||
rcu_is_callbacks_kthread()));
|
||||
false));
|
||||
}
|
||||
|
||||
static void rcu_process_callbacks(struct softirq_action *unused)
|
||||
{
|
||||
__rcu_process_callbacks(&rcu_sched_ctrlblk);
|
||||
__rcu_process_callbacks(&rcu_bh_ctrlblk);
|
||||
rcu_preempt_process_callbacks();
|
||||
}
|
||||
|
||||
/*
|
||||
@ -382,3 +378,8 @@ void call_rcu_bh(struct rcu_head *head, void (*func)(struct rcu_head *rcu))
|
||||
__call_rcu(head, func, &rcu_bh_ctrlblk);
|
||||
}
|
||||
EXPORT_SYMBOL_GPL(call_rcu_bh);
|
||||
|
||||
void rcu_init(void)
|
||||
{
|
||||
open_softirq(RCU_SOFTIRQ, rcu_process_callbacks);
|
||||
}
|
||||
|
||||
File diff suppressed because it is too large
Load Diff
@ -695,44 +695,6 @@ static struct rcu_torture_ops srcu_sync_ops = {
|
||||
.name = "srcu_sync"
|
||||
};
|
||||
|
||||
static int srcu_torture_read_lock_raw(void) __acquires(&srcu_ctl)
|
||||
{
|
||||
return srcu_read_lock_raw(&srcu_ctl);
|
||||
}
|
||||
|
||||
static void srcu_torture_read_unlock_raw(int idx) __releases(&srcu_ctl)
|
||||
{
|
||||
srcu_read_unlock_raw(&srcu_ctl, idx);
|
||||
}
|
||||
|
||||
static struct rcu_torture_ops srcu_raw_ops = {
|
||||
.init = rcu_sync_torture_init,
|
||||
.readlock = srcu_torture_read_lock_raw,
|
||||
.read_delay = srcu_read_delay,
|
||||
.readunlock = srcu_torture_read_unlock_raw,
|
||||
.completed = srcu_torture_completed,
|
||||
.deferred_free = srcu_torture_deferred_free,
|
||||
.sync = srcu_torture_synchronize,
|
||||
.call = NULL,
|
||||
.cb_barrier = NULL,
|
||||
.stats = srcu_torture_stats,
|
||||
.name = "srcu_raw"
|
||||
};
|
||||
|
||||
static struct rcu_torture_ops srcu_raw_sync_ops = {
|
||||
.init = rcu_sync_torture_init,
|
||||
.readlock = srcu_torture_read_lock_raw,
|
||||
.read_delay = srcu_read_delay,
|
||||
.readunlock = srcu_torture_read_unlock_raw,
|
||||
.completed = srcu_torture_completed,
|
||||
.deferred_free = rcu_sync_torture_deferred_free,
|
||||
.sync = srcu_torture_synchronize,
|
||||
.call = NULL,
|
||||
.cb_barrier = NULL,
|
||||
.stats = srcu_torture_stats,
|
||||
.name = "srcu_raw_sync"
|
||||
};
|
||||
|
||||
static void srcu_torture_synchronize_expedited(void)
|
||||
{
|
||||
synchronize_srcu_expedited(&srcu_ctl);
|
||||
@ -1983,7 +1945,6 @@ rcu_torture_init(void)
|
||||
{ &rcu_ops, &rcu_sync_ops, &rcu_expedited_ops,
|
||||
&rcu_bh_ops, &rcu_bh_sync_ops, &rcu_bh_expedited_ops,
|
||||
&srcu_ops, &srcu_sync_ops, &srcu_expedited_ops,
|
||||
&srcu_raw_ops, &srcu_raw_sync_ops,
|
||||
&sched_ops, &sched_sync_ops, &sched_expedited_ops, };
|
||||
|
||||
mutex_lock(&fullstop_mutex);
|
||||
|
||||
@ -218,8 +218,8 @@ module_param(blimit, long, 0444);
|
||||
module_param(qhimark, long, 0444);
|
||||
module_param(qlowmark, long, 0444);
|
||||
|
||||
static ulong jiffies_till_first_fqs = RCU_JIFFIES_TILL_FORCE_QS;
|
||||
static ulong jiffies_till_next_fqs = RCU_JIFFIES_TILL_FORCE_QS;
|
||||
static ulong jiffies_till_first_fqs = ULONG_MAX;
|
||||
static ulong jiffies_till_next_fqs = ULONG_MAX;
|
||||
|
||||
module_param(jiffies_till_first_fqs, ulong, 0644);
|
||||
module_param(jiffies_till_next_fqs, ulong, 0644);
|
||||
@ -3171,11 +3171,25 @@ static void __init rcu_init_one(struct rcu_state *rsp,
|
||||
*/
|
||||
static void __init rcu_init_geometry(void)
|
||||
{
|
||||
ulong d;
|
||||
int i;
|
||||
int j;
|
||||
int n = nr_cpu_ids;
|
||||
int rcu_capacity[MAX_RCU_LVLS + 1];
|
||||
|
||||
/*
|
||||
* Initialize any unspecified boot parameters.
|
||||
* The default values of jiffies_till_first_fqs and
|
||||
* jiffies_till_next_fqs are set to the RCU_JIFFIES_TILL_FORCE_QS
|
||||
* value, which is a function of HZ, then adding one for each
|
||||
* RCU_JIFFIES_FQS_DIV CPUs that might be on the system.
|
||||
*/
|
||||
d = RCU_JIFFIES_TILL_FORCE_QS + nr_cpu_ids / RCU_JIFFIES_FQS_DIV;
|
||||
if (jiffies_till_first_fqs == ULONG_MAX)
|
||||
jiffies_till_first_fqs = d;
|
||||
if (jiffies_till_next_fqs == ULONG_MAX)
|
||||
jiffies_till_next_fqs = d;
|
||||
|
||||
/* If the compile-time values are accurate, just leave. */
|
||||
if (rcu_fanout_leaf == CONFIG_RCU_FANOUT_LEAF &&
|
||||
nr_cpu_ids == NR_CPUS)
|
||||
|
||||
@ -343,12 +343,17 @@ struct rcu_data {
|
||||
#define RCU_FORCE_QS 3 /* Need to force quiescent state. */
|
||||
#define RCU_SIGNAL_INIT RCU_SAVE_DYNTICK
|
||||
|
||||
#define RCU_JIFFIES_TILL_FORCE_QS 3 /* for rsp->jiffies_force_qs */
|
||||
#define RCU_JIFFIES_TILL_FORCE_QS (1 + (HZ > 250) + (HZ > 500))
|
||||
/* For jiffies_till_first_fqs and */
|
||||
/* and jiffies_till_next_fqs. */
|
||||
|
||||
#define RCU_STALL_RAT_DELAY 2 /* Allow other CPUs time */
|
||||
/* to take at least one */
|
||||
/* scheduling clock irq */
|
||||
/* before ratting on them. */
|
||||
#define RCU_JIFFIES_FQS_DIV 256 /* Very large systems need more */
|
||||
/* delay between bouts of */
|
||||
/* quiescent-state forcing. */
|
||||
|
||||
#define RCU_STALL_RAT_DELAY 2 /* Allow other CPUs time to take */
|
||||
/* at least one scheduling clock */
|
||||
/* irq before ratting on them. */
|
||||
|
||||
#define rcu_wait(cond) \
|
||||
do { \
|
||||
|
||||
@ -81,7 +81,7 @@ static void __init rcu_bootup_announce_oddness(void)
|
||||
pr_info("\tFour-level hierarchy is enabled.\n");
|
||||
#endif
|
||||
if (rcu_fanout_leaf != CONFIG_RCU_FANOUT_LEAF)
|
||||
pr_info("\tExperimental boot-time adjustment of leaf fanout to %d.\n", rcu_fanout_leaf);
|
||||
pr_info("\tBoot-time adjustment of leaf fanout to %d.\n", rcu_fanout_leaf);
|
||||
if (nr_cpu_ids != NR_CPUS)
|
||||
pr_info("\tRCU restricting CPUs from NR_CPUS=%d to nr_cpu_ids=%d.\n", NR_CPUS, nr_cpu_ids);
|
||||
#ifdef CONFIG_RCU_NOCB_CPU
|
||||
@ -91,19 +91,19 @@ static void __init rcu_bootup_announce_oddness(void)
|
||||
have_rcu_nocb_mask = true;
|
||||
}
|
||||
#ifdef CONFIG_RCU_NOCB_CPU_ZERO
|
||||
pr_info("\tExperimental no-CBs CPU 0\n");
|
||||
pr_info("\tOffload RCU callbacks from CPU 0\n");
|
||||
cpumask_set_cpu(0, rcu_nocb_mask);
|
||||
#endif /* #ifdef CONFIG_RCU_NOCB_CPU_ZERO */
|
||||
#ifdef CONFIG_RCU_NOCB_CPU_ALL
|
||||
pr_info("\tExperimental no-CBs for all CPUs\n");
|
||||
pr_info("\tOffload RCU callbacks from all CPUs\n");
|
||||
cpumask_setall(rcu_nocb_mask);
|
||||
#endif /* #ifdef CONFIG_RCU_NOCB_CPU_ALL */
|
||||
#endif /* #ifndef CONFIG_RCU_NOCB_CPU_NONE */
|
||||
if (have_rcu_nocb_mask) {
|
||||
cpulist_scnprintf(nocb_buf, sizeof(nocb_buf), rcu_nocb_mask);
|
||||
pr_info("\tExperimental no-CBs CPUs: %s.\n", nocb_buf);
|
||||
pr_info("\tOffload RCU callbacks from CPUs: %s.\n", nocb_buf);
|
||||
if (rcu_nocb_poll)
|
||||
pr_info("\tExperimental polled no-CBs CPUs.\n");
|
||||
pr_info("\tPoll for callbacks from no-CBs CPUs.\n");
|
||||
}
|
||||
#endif /* #ifdef CONFIG_RCU_NOCB_CPU */
|
||||
}
|
||||
@ -932,6 +932,24 @@ static void __init __rcu_init_preempt(void)
|
||||
rcu_init_one(&rcu_preempt_state, &rcu_preempt_data);
|
||||
}
|
||||
|
||||
/*
|
||||
* Check for a task exiting while in a preemptible-RCU read-side
|
||||
* critical section, clean up if so. No need to issue warnings,
|
||||
* as debug_check_no_locks_held() already does this if lockdep
|
||||
* is enabled.
|
||||
*/
|
||||
void exit_rcu(void)
|
||||
{
|
||||
struct task_struct *t = current;
|
||||
|
||||
if (likely(list_empty(¤t->rcu_node_entry)))
|
||||
return;
|
||||
t->rcu_read_lock_nesting = 1;
|
||||
barrier();
|
||||
t->rcu_read_unlock_special = RCU_READ_UNLOCK_BLOCKED;
|
||||
__rcu_read_unlock();
|
||||
}
|
||||
|
||||
#else /* #ifdef CONFIG_TREE_PREEMPT_RCU */
|
||||
|
||||
static struct rcu_state *rcu_state = &rcu_sched_state;
|
||||
@ -1100,6 +1118,14 @@ static void __init __rcu_init_preempt(void)
|
||||
{
|
||||
}
|
||||
|
||||
/*
|
||||
* Because preemptible RCU does not exist, tasks cannot possibly exit
|
||||
* while in preemptible RCU read-side critical sections.
|
||||
*/
|
||||
void exit_rcu(void)
|
||||
{
|
||||
}
|
||||
|
||||
#endif /* #else #ifdef CONFIG_TREE_PREEMPT_RCU */
|
||||
|
||||
#ifdef CONFIG_RCU_BOOST
|
||||
|
||||
Loading…
Reference in New Issue
Block a user