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The trace_rcu_dyntick() trace event did not print both the old and
the new value of the nesting level, and furthermore printed only
the low-order 32 bits of it. This could result in some confusion
when interpreting trace-event dumps, so this commit prints both
the old and the new value, prints the full 64 bits, and also selects
the process-entry/exit increment to print nicely in hexadecimal.
Signed-off-by: Paul E. McKenney <paul.mckenney@linaro.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>
It is assumed that rcu won't be used once we switch to tickless
mode and until we restart the tick. However this is not always
true, as in x86-64 where we dereference the idle notifiers after
the tick is stopped.
To prepare for fixing this, add two new APIs:
tick_nohz_idle_enter_norcu() and tick_nohz_idle_exit_norcu().
If no use of RCU is made in the idle loop between
tick_nohz_enter_idle() and tick_nohz_exit_idle() calls, the arch
must instead call the new *_norcu() version such that the arch doesn't
need to call rcu_idle_enter() and rcu_idle_exit().
Otherwise the arch must call tick_nohz_enter_idle() and
tick_nohz_exit_idle() and also call explicitly:
- rcu_idle_enter() after its last use of RCU before the CPU is put
to sleep.
- rcu_idle_exit() before the first use of RCU after the CPU is woken
up.
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Mike Frysinger <vapier@gentoo.org>
Cc: Guan Xuetao <gxt@mprc.pku.edu.cn>
Cc: David Miller <davem@davemloft.net>
Cc: Chris Metcalf <cmetcalf@tilera.com>
Cc: Hans-Christian Egtvedt <hans-christian.egtvedt@atmel.com>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Russell King <linux@arm.linux.org.uk>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: Paul Mundt <lethal@linux-sh.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
The tick_nohz_stop_sched_tick() function, which tries to delay
the next timer tick as long as possible, can be called from two
places:
- From the idle loop to start the dytick idle mode
- From interrupt exit if we have interrupted the dyntick
idle mode, so that we reprogram the next tick event in
case the irq changed some internal state that requires this
action.
There are only few minor differences between both that
are handled by that function, driven by the ts->inidle
cpu variable and the inidle parameter. The whole guarantees
that we only update the dyntick mode on irq exit if we actually
interrupted the dyntick idle mode, and that we enter in RCU extended
quiescent state from idle loop entry only.
Split this function into:
- tick_nohz_idle_enter(), which sets ts->inidle to 1, enters
dynticks idle mode unconditionally if it can, and enters into RCU
extended quiescent state.
- tick_nohz_irq_exit() which only updates the dynticks idle mode
when ts->inidle is set (ie: if tick_nohz_idle_enter() has been called).
To maintain symmetry, tick_nohz_restart_sched_tick() has been renamed
into tick_nohz_idle_exit().
This simplifies the code and micro-optimize the irq exit path (no need
for local_irq_save there). This also prepares for the split between
dynticks and rcu extended quiescent state logics. We'll need this split to
further fix illegal uses of RCU in extended quiescent states in the idle
loop.
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Mike Frysinger <vapier@gentoo.org>
Cc: Guan Xuetao <gxt@mprc.pku.edu.cn>
Cc: David Miller <davem@davemloft.net>
Cc: Chris Metcalf <cmetcalf@tilera.com>
Cc: Hans-Christian Egtvedt <hans-christian.egtvedt@atmel.com>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Russell King <linux@arm.linux.org.uk>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: Paul Mundt <lethal@linux-sh.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>
Inform the user if an RCU usage error is detected by lockdep while in
an extended quiescent state (in this case, the RCU-free window in idle).
This is accomplished by adding a line to the RCU lockdep splat indicating
whether or not the splat occurred in extended quiescent state.
Uses of RCU from within extended quiescent state mode are totally ignored
by RCU, hence the importance of this diagnostic.
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Lai Jiangshan <laijs@cn.fujitsu.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>
Report that none of the rcu read lock maps are held while in an RCU
extended quiescent state (the section between rcu_idle_enter()
and rcu_idle_exit()). This helps detect any use of rcu_dereference()
and friends from within the section in idle where RCU is not allowed.
This way we can guarantee an extended quiescent window where the CPU
can be put in dyntick idle mode or can simply aoid to be part of any
global grace period completion while in the idle loop.
Uses of RCU from such mode are totally ignored by RCU, hence the
importance of these checks.
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Lai Jiangshan <laijs@cn.fujitsu.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>
Empty void functions do not need "return", so this commit removes it
from rcu_report_exp_rnp().
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
When setting up an expedited grace period, if there were no readers, the
task will awaken itself. This commit removes this useless self-awakening.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Because rcu_is_cpu_idle() is to be used to check for extended quiescent
states in RCU-preempt read-side critical sections, it cannot assume that
preemption is disabled. And preemption must be disabled when accessing
the dyntick-idle state, because otherwise the following sequence of events
could occur:
1. Task A on CPU 1 enters rcu_is_cpu_idle() and picks up the pointer
to CPU 1's per-CPU variables.
2. Task B preempts Task A and starts running on CPU 1.
3. Task A migrates to CPU 2.
4. Task B blocks, leaving CPU 1 idle.
5. Task A continues execution on CPU 2, accessing CPU 1's dyntick-idle
information using the pointer fetched in step 1 above, and finds
that CPU 1 is idle.
6. Task A therefore incorrectly concludes that it is executing in
an extended quiescent state, possibly issuing a spurious splat.
Therefore, this commit disables preemption within the rcu_is_cpu_idle()
function.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>
Trace the rcutorture RCU accesses and dump the trace buffer when the
first failure is detected.
Signed-off-by: Paul E. McKenney <paul.mckenney@linaro.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>
Add an EXPORT_SYMBOL_GPL() so that rcutorture can dump the trace buffer
upon detection of an RCU error.
Signed-off-by: Paul E. McKenney <paul.mckenney@linaro.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>
Earlier versions of RCU used the scheduling-clock tick to detect idleness
by checking for the idle task, but handled idleness differently for
CONFIG_NO_HZ=y. But there are now a number of uses of RCU read-side
critical sections in the idle task, for example, for tracing. A more
fine-grained detection of idleness is therefore required.
This commit presses the old dyntick-idle code into full-time service,
so that rcu_idle_enter(), previously known as rcu_enter_nohz(), is
always invoked at the beginning of an idle loop iteration. Similarly,
rcu_idle_exit(), previously known as rcu_exit_nohz(), is always invoked
at the end of an idle-loop iteration. This allows the idle task to
use RCU everywhere except between consecutive rcu_idle_enter() and
rcu_idle_exit() calls, in turn allowing architecture maintainers to
specify exactly where in the idle loop that RCU may be used.
Because some of the userspace upcall uses can result in what looks
to RCU like half of an interrupt, it is not possible to expect that
the irq_enter() and irq_exit() hooks will give exact counts. This
patch therefore expands the ->dynticks_nesting counter to 64 bits
and uses two separate bitfields to count process/idle transitions
and interrupt entry/exit transitions. It is presumed that userspace
upcalls do not happen in the idle loop or from usermode execution
(though usermode might do a system call that results in an upcall).
The counter is hard-reset on each process/idle transition, which
avoids the interrupt entry/exit error from accumulating. Overflow
is avoided by the 64-bitness of the ->dyntick_nesting counter.
This commit also adds warnings if a non-idle task asks RCU to enter
idle state (and these checks will need some adjustment before applying
Frederic's OS-jitter patches (http://lkml.org/lkml/2011/10/7/246).
In addition, validation of ->dynticks and ->dynticks_nesting is added.
Signed-off-by: Paul E. McKenney <paul.mckenney@linaro.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>
When synchronize_sched_expedited() takes its second and subsequent
snapshots of sync_sched_expedited_started, it subtracts 1. This
means that the concurrent caller of synchronize_sched_expedited()
that incremented to that value sees our successful completion, it
will not be able to take advantage of it. This restriction is
pointless, given that our full expedited grace period would have
happened after the other guy started, and thus should be able to
serve as a proxy for the other guy successfully executing
try_stop_cpus().
This commit therefore removes the subtraction of 1.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>
Because rcu_read_unlock_special() samples rcu_preempted_readers_exp(rnp)
after dropping rnp->lock, the following sequence of events is possible:
1. Task A exits its RCU read-side critical section, and removes
itself from the ->blkd_tasks list, releases rnp->lock, and is
then preempted. Task B remains on the ->blkd_tasks list, and
blocks the current expedited grace period.
2. Task B exits from its RCU read-side critical section and removes
itself from the ->blkd_tasks list. Because it is the last task
blocking the current expedited grace period, it ends that
expedited grace period.
3. Task A resumes, and samples rcu_preempted_readers_exp(rnp) which
of course indicates that nothing is blocking the nonexistent
expedited grace period. Task A is again preempted.
4. Some other CPU starts an expedited grace period. There are several
tasks blocking this expedited grace period queued on the
same rcu_node structure that Task A was using in step 1 above.
5. Task A examines its state and incorrectly concludes that it was
the last task blocking the expedited grace period on the current
rcu_node structure. It therefore reports completion up the
rcu_node tree.
6. The expedited grace period can then incorrectly complete before
the tasks blocked on this same rcu_node structure exit their
RCU read-side critical sections. Arbitrarily bad things happen.
This commit therefore takes a snapshot of rcu_preempted_readers_exp(rnp)
prior to dropping the lock, so that only the last task thinks that it is
the last task, thus avoiding the failure scenario laid out above.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>
The ->signaled field was named before complications in the form of
dyntick-idle mode and offlined CPUs. These complications have required
that force_quiescent_state() be implemented as a state machine, instead
of simply unconditionally sending reschedule IPIs. Therefore, this
commit renames ->signaled to ->fqs_state to catch up with the new
force_quiescent_state() reality.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>
Several snapshot ioctls were marked for removal quite some time ago,
since they were deprecated. Remove them.
Suggested-by: Rafael J. Wysocki <rjw@sisk.pl>
Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
Commit a144c6a (PM: Print a warning if firmware is requested when tasks
are frozen) introduced usermodehelper_is_disabled() to warn and exit
immediately if firmware is requested when usermodehelpers are disabled.
However, it is racy. Consider the following scenario, currently used in
drivers/base/firmware_class.c:
...
if (usermodehelper_is_disabled())
goto out;
/* Do actual work */
...
out:
return err;
Nothing prevents someone from disabling usermodehelpers just after the check
in the 'if' condition, which means that it is quite possible to try doing the
"actual work" with usermodehelpers disabled, leading to undesirable
consequences.
In particular, this race condition in _request_firmware() causes task freezing
failures whenever suspend/hibernation is in progress because, it wrongly waits
to get the firmware/microcode image from userspace when actually the
usermodehelpers are disabled or userspace has been frozen.
Some of the example scenarios that cause freezing failures due to this race
are those that depend on userspace via request_firmware(), such as x86
microcode module initialization and microcode image reload.
Previous discussions about this issue can be found at:
http://thread.gmane.org/gmane.linux.kernel/1198291/focus=1200591
This patch adds proper synchronization to fix this issue.
It is to be noted that this patchset fixes the freezing failures but doesn't
remove the warnings. IOW, it does not attempt to add explicit synchronization
to x86 microcode driver to avoid requesting microcode image at inopportune
moments. Because, the warnings were introduced to highlight such cases, in the
first place. And we need not silence the warnings, since we take care of the
*real* problem (freezing failure) and hence, after that, the warnings are
pretty harmless anyway.
Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
* 'perf-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
perf: Do no try to schedule task events if there are none
lockdep, kmemcheck: Annotate ->lock in lockdep_init_map()
perf header: Use event_name() to get an event name
perf stat: Failure with "Operation not supported"
In order to safely dereference current->real_parent inside an
rcu_read_lock, we need an rcu_dereference.
Signed-off-by: Mandeep Singh Baines <msb@chromium.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Pavel Emelyanov <xemul@openvz.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Kees Cook <keescook@chromium.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Commit 4f2a8d3cf5e ("printk: Fix console_sem vs logbuf_lock unlock race")
introduced another silly bug where we would want to acquire an already
held lock. Avoid this.
Reported-by: Andrea Arcangeli <aarcange@redhat.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Using [un]lock_system_sleep() is safer than directly using mutex_[un]lock()
on 'pm_mutex', since the latter could lead to freezing failures. Hence convert
all the present users of mutex_[un]lock(&pm_mutex) to use these safe APIs
instead.
Suggested-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
Reviewed-by: Simon Horman <horms@verge.net.au>
Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
Yong Zhang reported:
> [ INFO: suspicious RCU usage. ]
> kernel/sched/fair.c:5091 suspicious rcu_dereference_check() usage!
This is due to the sched_domain stuff being RCU protected and
commit 0b005cf5 ("sched, nohz: Implement sched group, domain
aware nohz idle load balancing") overlooking this fact.
The sd variable only lives inside the for_each_domain() block,
so we only need to wrap that.
Reported-by: Yong Zhang <yong.zhang0@gmail.com>
Tested-by: Yong Zhang <yong.zhang0@gmail.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Suresh Siddha <suresh.b.siddha@intel.com>
Link: http://lkml.kernel.org/r/1323264728.32012.107.camel@twins
Signed-off-by: Ingo Molnar <mingo@elte.hu>
We do want to allow lock debugging for GPL-compatible modules
that are not (yet) built in-tree. This was disabled as a
side-effect of commit 2449b8ba0745327c5fa49a8d9acffe03b2eded69
('module,bug: Add TAINT_OOT_MODULE flag for modules not built
in-tree'). Lock debug warnings now include taint flags, so
kernel developers should still be able to deflect warnings
caused by out-of-tree modules.
The TAINT_PROPRIETARY_MODULE flag for non-GPL-compatible modules
will still disable lock debugging.
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
Cc: Nick Bowler <nbowler@elliptictech.com>
Cc: Greg KH <greg@kroah.com>
Cc: Dave Jones <davej@redhat.com>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: Randy Dunlap <rdunlap@xenotime.net>
Cc: Debian kernel maintainers <debian-kernel@lists.debian.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Alan Cox <alan@linux.intel.com>
Link: http://lkml.kernel.org/r/1323268258.18450.11.camel@deadeye
Signed-off-by: Ingo Molnar <mingo@elte.hu>
perf_event_sched_in() shouldn't try to schedule task events if there
are none otherwise task's ctx->is_active will be set and will not be
cleared during sched_out. This will prevent newly added events from
being scheduled into the task context.
Fixes a boo-boo in commit 1d5f003f5a9 ("perf: Do not set task_ctx
pointer in cpuctx if there are no events in the context").
Signed-off-by: Gleb Natapov <gleb@redhat.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/20111122140821.GF2557@redhat.com
Signed-off-by: Ingo Molnar <mingo@elte.hu>
In the snapshot_ioctl() function, under SNAPSHOT_FREEZE, the code below
freeze_processes() is a bit unintuitive. Improve it by replacing the
second 'if' condition with an 'else' clause.
Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
* pm-freezer: (26 commits)
Freezer / sunrpc / NFS: don't allow TASK_KILLABLE sleeps to block the freezer
Freezer: fix more fallout from the thaw_process rename
freezer: fix wait_event_freezable/__thaw_task races
freezer: kill unused set_freezable_with_signal()
dmatest: don't use set_freezable_with_signal()
usb_storage: don't use set_freezable_with_signal()
freezer: remove unused @sig_only from freeze_task()
freezer: use lock_task_sighand() in fake_signal_wake_up()
freezer: restructure __refrigerator()
freezer: fix set_freezable[_with_signal]() race
freezer: remove should_send_signal() and update frozen()
freezer: remove now unused TIF_FREEZE
freezer: make freezing() test freeze conditions in effect instead of TIF_FREEZE
cgroup_freezer: prepare for removal of TIF_FREEZE
freezer: clean up freeze_processes() failure path
freezer: kill PF_FREEZING
freezer: test freezable conditions while holding freezer_lock
freezer: make freezing indicate freeze condition in effect
freezer: use dedicated lock instead of task_lock() + memory barrier
freezer: don't distinguish nosig tasks on thaw
...
The hibernation test modes 'test' and 'testproc' are deprecated, because
the 'pm_test' framework offers much more fine-grained control for debugging
suspend and hibernation related problems.
So, remove the deprecated 'test' and 'testproc' hibernation test modes.
Suggested-by: Rafael J. Wysocki <rjw@sisk.pl>
Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
Commit 2aede851ddf08666f68ffc17be446420e9d2a056 (PM / Hibernate: Freeze
kernel threads after preallocating memory) moved the freezing of kernel
threads to hibernation_snapshot() function.
So now, if the call to hibernation_snapshot() returns early due to a
successful hibernation test, the caller has to thaw processes to ensure
that the system gets back to its original state.
But in SNAPSHOT_CREATE_IMAGE hibernation ioctl, the caller does not thaw
processes in case hibernation_snapshot() returned due to a successful
freezer test. Fix this issue. But note we still send the value of 'in_suspend'
(which is now 0) to userspace, because we are not in an error path per-se,
and moreover, the value of in_suspend correctly depicts the situation here.
Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
In the software_resume() function defined in kernel/power/hibernate.c,
if the call to create_basic_memory_bitmaps() fails, the usermodehelpers
are not enabled (which had been disabled in the previous step). Fix it.
Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
* 'perf-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
ftrace: Fix hash record accounting bug
perf: Fix parsing of __print_flags() in TP_printk()
jump_label: jump_label_inc may return before the code is patched
ftrace: Remove force undef config value left for testing
tracing: Restore system filter behavior
tracing: fix event_subsystem ref counting
Intention is to set the NOHZ_BALANCE_KICK flag for the 'ilb_cpu'. Not
for the 'cpu' which is the local cpu. Fix the typo.
Reported-by: Srivatsa Vaddagiri <vatsa@linux.vnet.ibm.com>
Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1323199594.1984.18.camel@sbsiddha-desk.sc.intel.com
Signed-off-by: Ingo Molnar <mingo@elte.hu>
cpu bit in the nohz.idle_cpu_mask are reset in the first busy tick after
exiting idle. So during nohz_idle_balance(), intention is to double
check if the cpu that is part of the idle_cpu_mask is indeed idle before
going ahead in performing idle balance for that cpu.
Fix the cpu typo in the idle_cpu() check during nohz_idle_balance().
Reported-by: Srivatsa Vaddagiri <vatsa@linux.vnet.ibm.com>
Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1323199177.1984.12.camel@sbsiddha-desk.sc.intel.com
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Now that we initialize jump_labels before sched_init() we can use them
for the debug features without having to worry about a window where
they have the wrong setting.
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/n/tip-vpreo4hal9e0kzqmg5y0io2k@git.kernel.org
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Now that we're pointing cpuacct's root cgroup to cpustat and accounting
through task_group_account_field(), we should not access cpustat directly.
Since it is done anyway inside the acessor function, we end up accounting
it twice, which is wrong.
Signed-off-by: Glauber Costa <glommer@parallels.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1322863119-14225-2-git-send-email-glommer@parallels.com
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Right now, after we collect tick statistics for user and system and store them
in a well known location, we keep the same statistics again for cpuacct.
Since cpuacct is hierarchical, the numbers for the root cgroup should be
absolutely equal to the system-wide numbers.
So it would be better to just use it: this patch changes cpuacct accounting
in a way that the cpustat statistics are kept in a struct kernel_cpustat percpu
array. In the root cgroup case, we just point it to the main array. The rest of
the hierarchy walk can be totally disabled later with a static branch - but I am
not doing it here.
Signed-off-by: Glauber Costa <glommer@parallels.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Paul Tuner <pjt@google.com>
Link: http://lkml.kernel.org/r/1322498719-2255-4-git-send-email-glommer@parallels.com
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Provide two initializers for jump_label_key that initialize it enabled
or disabled. Also modify all jump_label code to allow for jump_labels to be
initialized enabled.
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Jason Baron <jbaron@redhat.com>
Link: http://lkml.kernel.org/n/tip-p40e3yj21b68y03z1yv825e7@git.kernel.org
Signed-off-by: Ingo Molnar <mingo@elte.hu>
WARNING: arch/x86/kernel/built-in.o(.text+0x4c71): Section mismatch in
reference from the function arch_jump_label_transform_static() to the
function .init.text:text_poke_early()
The function arch_jump_label_transform_static() references
the function __init text_poke_early().
This is often because arch_jump_label_transform_static lacks a __init
annotation or the annotation of text_poke_early is wrong.
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Jason Baron <jbaron@redhat.com>
Link: http://lkml.kernel.org/n/tip-9lefe89mrvurrwpqw5h8xm8z@git.kernel.org
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Since commit f59de89 ("lockdep: Clear whole lockdep_map on initialization"),
lockdep_init_map() will clear all the struct. But it will break
lock_set_class()/lock_set_subclass(). A typical race condition
is like below:
CPU A CPU B
lock_set_subclass(lockA);
lock_set_class(lockA);
lockdep_init_map(lockA);
/* lockA->name is cleared */
memset(lockA);
__lock_acquire(lockA);
/* lockA->class_cache[] is cleared */
register_lock_class(lockA);
look_up_lock_class(lockA);
WARN_ON_ONCE(class->name !=
lock->name);
lock->name = name;
So restore to what we have done before commit f59de89 but annotate
->lock with kmemcheck_mark_initialized() to suppress the kmemcheck
warning reported in commit f59de89.
Reported-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Reported-by: Borislav Petkov <bp@alien8.de>
Suggested-by: Vegard Nossum <vegard.nossum@gmail.com>
Signed-off-by: Yong Zhang <yong.zhang0@gmail.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: David Rientjes <rientjes@google.com>
Cc: <stable@kernel.org>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/20111109080451.GB8124@zhy
Signed-off-by: Ingo Molnar <mingo@elte.hu>
The expiry function compares the timer against current time and does
not expire the timer when the expiry time is >= now. That's wrong. If
the timer is set for now, then it must expire.
Make the condition expiry > now for breaking out the loop.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: John Stultz <john.stultz@linaro.org>
Cc: stable@kernel.org
We already have a pointer to the cgroup parent (whose data is more likely
to be in the cache than this, anyway), so there is no need to have this one
in cpuacct.
This patch makes the underlying cgroup be used instead.
Signed-off-by: Glauber Costa <glommer@parallels.com>
Reviewed-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Paul Tuner <pjt@google.com>
Cc: Li Zefan <lizf@cn.fujitsu.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1322498719-2255-3-git-send-email-glommer@parallels.com
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This patch changes fields in cpustat from a structure, to an
u64 array. Math gets easier, and the code is more flexible.
Signed-off-by: Glauber Costa <glommer@parallels.com>
Reviewed-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Paul Tuner <pjt@google.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1322498719-2255-2-git-send-email-glommer@parallels.com
Signed-off-by: Ingo Molnar <mingo@elte.hu>
nr_busy_cpus in the sched_group_power indicates whether the group
is semi idle or not. This helps remove the is_semi_idle_group() and simplify
the find_new_ilb() in the context of finding an optimal cpu that can do
idle load balancing.
Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/20111202010832.656983582@sbsiddha-desk.sc.intel.com
Signed-off-by: Ingo Molnar <mingo@elte.hu>
When there are many logical cpu's that enter and exit idle often, members of
the global nohz data structure are getting modified very frequently causing
lot of cache-line contention.
Make the nohz idle load balancing more scalabale by using the sched domain
topology and 'nr_busy_cpu's in the struct sched_group_power.
Idle load balance is kicked on one of the idle cpu's when there is atleast
one idle cpu and:
- a busy rq having more than one task or
- a busy rq's scheduler group that share package resources (like HT/MC
siblings) and has more than one member in that group busy or
- for the SD_ASYM_PACKING domain, if the lower numbered cpu's in that
domain are idle compared to the busy ones.
This will help in kicking the idle load balancing request only when
there is a potential imbalance. And once it is mostly balanced, these kicks will
be minimized.
These changes helped improve the workload that is context switch intensive
between number of task pairs by 2x on a 8 socket NHM-EX based system.
Reported-by: Tim Chen <tim.c.chen@intel.com>
Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/20111202010832.602203411@sbsiddha-desk.sc.intel.com
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Introduce nr_busy_cpus in the struct sched_group_power [Not in sched_group
because sched groups are duplicated for the SD_OVERLAP scheduler domain]
and for each cpu that enters and exits idle, this parameter will
be updated in each scheduler group of the scheduler domain that this cpu
belongs to.
To avoid the frequent update of this state as the cpu enters
and exits idle, the update of the stat during idle exit is
delayed to the first timer tick that happens after the cpu becomes busy.
This is done using NOHZ_IDLE flag in the struct rq's nohz_flags.
Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/20111202010832.555984323@sbsiddha-desk.sc.intel.com
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Introduce nohz_flags in the struct rq, which will track these two flags
for now.
NOHZ_TICK_STOPPED keeps track of the tick stopped status that gets set when
the tick is stopped. It will be used to update the nohz idle load balancer data
structures during the first busy tick after the tick is restarted. At this
first busy tick after tickless idle, NOHZ_TICK_STOPPED flag will be reset.
This will minimize the nohz idle load balancer status updates that currently
happen for every tickless exit, making it more scalable when there
are many logical cpu's that enter and exit idle often.
NOHZ_BALANCE_KICK will track the need for nohz idle load balance
on this rq. This will replace the nohz_balance_kick in the rq, which was
not being updated atomically.
Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/20111202010832.499438999@sbsiddha-desk.sc.intel.com
Signed-off-by: Ingo Molnar <mingo@elte.hu>
The second call to sched_rt_period() is redundant, because the value of the
rt_runtime was already read and it was protected by the ->rt_runtime_lock.
Signed-off-by: Shan Hai <haishan.bai@gmail.com>
Reviewed-by: Kamalesh Babulal <kamalesh@linux.vnet.ibm.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1322535836-13590-2-git-send-email-haishan.bai@gmail.com
Signed-off-by: Ingo Molnar <mingo@elte.hu>
