linux-toradex.git/kernel/events/core.c, branch v3.10.51

perf: Enforce 1 as lower limit for perf_event_max_sample_rate

2014-06-11T19:03:27+00:00

commit 723478c8a471403c53cf144999701f6e0c4bbd11 upstream.

/proc/sys/kernel/perf_event_max_sample_rate will accept
negative values as well as 0.

Negative values are unreasonable, and 0 causes a
divide by zero exception in perf_proc_update_handler.

This patch enforces a lower limit of 1.

Signed-off-by: Knut Petersen 
Signed-off-by: Peter Zijlstra 
Link: http://lkml.kernel.org/r/5242DB0C.4070005@t-online.de
Signed-off-by: Ingo Molnar 
Cc: Weng Meiling 
Signed-off-by: Greg Kroah-Hartman

perf: Fix interrupt handler timing harness

2014-06-11T19:03:27+00:00

commit e5302920da9ef23f9d19d4e9ac85704cc25bee7a upstream.

This patch fixes a serious bug in:

  14c63f17b1fd perf: Drop sample rate when sampling is too slow

There was an misunderstanding on the API of the do_div()
macro. It returns the remainder of the division and this
was not what the function expected leading to disabling the
interrupt latency watchdog.

This patch also remove a duplicate assignment in
perf_sample_event_took().

Signed-off-by: Stephane Eranian 
Cc: peterz@infradead.org
Cc: dave.hansen@linux.intel.com
Cc: ak@linux.intel.com
Cc: jolsa@redhat.com
Link: http://lkml.kernel.org/r/20130704223010.GA30625@quad
Signed-off-by: Ingo Molnar 
Cc: Weng Meiling 
Signed-off-by: Greg Kroah-Hartman

perf: Drop sample rate when sampling is too slow

2014-06-11T19:03:26+00:00

commit 14c63f17b1fde5a575a28e96547a22b451c71fb5 upstream.

This patch keeps track of how long perf's NMI handler is taking,
and also calculates how many samples perf can take a second.  If
the sample length times the expected max number of samples
exceeds a configurable threshold, it drops the sample rate.

This way, we don't have a runaway sampling process eating up the
CPU.

This patch can tend to drop the sample rate down to level where
perf doesn't work very well.  *BUT* the alternative is that my
system hangs because it spends all of its time handling NMIs.

I'll take a busted performance tool over an entire system that's
busted and undebuggable any day.

BTW, my suspicion is that there's still an underlying bug here.
Using the HPET instead of the TSC is definitely a contributing
factor, but I suspect there are some other things going on.
But, I can't go dig down on a bug like that with my machine
hanging all the time.

Signed-off-by: Dave Hansen 
Acked-by: Peter Zijlstra 
Cc: paulus@samba.org
Cc: acme@ghostprotocols.net
Cc: Dave Hansen 
[ Prettified it a bit. ]
Signed-off-by: Ingo Molnar 
Cc: Weng Meiling 
Signed-off-by: Greg Kroah-Hartman

perf: Fix race in removing an event

2014-06-11T19:03:21+00:00

commit 46ce0fe97a6be7532ce6126bb26ce89fed81528c upstream.

When removing a (sibling) event we do:

	raw_spin_lock_irq(&ctx->lock);
	perf_group_detach(event);
	raw_spin_unlock_irq(&ctx->lock);

	

	perf_remove_from_context(event);
		raw_spin_lock_irq(&ctx->lock);
		...
		raw_spin_unlock_irq(&ctx->lock);

Now, assuming the event is a sibling, it will be 'unreachable' for
things like ctx_sched_out() because that iterates the
groups->siblings, and we just unhooked the sibling.

So, if during  we get ctx_sched_out(), it will miss the event
and not call event_sched_out() on it, leaving it programmed on the
PMU.

The subsequent perf_remove_from_context() call will find the ctx is
inactive and only call list_del_event() to remove the event from all
other lists.

Hereafter we can proceed to free the event; while still programmed!

Close this hole by moving perf_group_detach() inside the same
ctx->lock region(s) perf_remove_from_context() has.

The condition on inherited events only in __perf_event_exit_task() is
likely complete crap because non-inherited events are part of groups
too and we're tearing down just the same. But leave that for another
patch.

Most-likely-Fixes: e03a9a55b4e ("perf: Change close() semantics for group events")
Reported-by: Vince Weaver 
Tested-by: Vince Weaver 
Much-staring-at-traces-by: Vince Weaver 
Much-staring-at-traces-by: Thomas Gleixner 
Cc: Arnaldo Carvalho de Melo 
Cc: Linus Torvalds 
Signed-off-by: Peter Zijlstra 
Link: http://lkml.kernel.org/r/20140505093124.GN17778@laptop.programming.kicks-ass.net
Signed-off-by: Ingo Molnar 
Signed-off-by: Greg Kroah-Hartman

perf: Limit perf_event_attr::sample_period to 63 bits

2014-06-11T19:03:21+00:00

commit 0819b2e30ccb93edf04876237b6205eef84ec8d2 upstream.

Vince reported that using a large sample_period (one with bit 63 set)
results in wreckage since while the sample_period is fundamentally
unsigned (negative periods don't make sense) the way we implement
things very much rely on signed logic.

So limit sample_period to 63 bits to avoid tripping over this.

Reported-by: Vince Weaver 
Signed-off-by: Peter Zijlstra 
Link: http://lkml.kernel.org/n/tip-p25fhunibl4y3qi0zuqmyf4b@git.kernel.org
Signed-off-by: Thomas Gleixner 
Signed-off-by: Greg Kroah-Hartman

perf: Prevent false warning in perf_swevent_add

2014-06-11T19:03:21+00:00

commit 39af6b1678afa5880dda7e375cf3f9d395087f6d upstream.

The perf cpu offline callback takes down all cpu context
events and releases swhash->swevent_hlist.

This could race with task context software event being just
scheduled on this cpu via perf_swevent_add while cpu hotplug
code already cleaned up event's data.

The race happens in the gap between the cpu notifier code
and the cpu being actually taken down. Note that only cpu
ctx events are terminated in the perf cpu hotplug code.

It's easily reproduced with:
  $ perf record -e faults perf bench sched pipe

while putting one of the cpus offline:
  # echo 0 > /sys/devices/system/cpu/cpu1/online

Console emits following warning:
  WARNING: CPU: 1 PID: 2845 at kernel/events/core.c:5672 perf_swevent_add+0x18d/0x1a0()
  Modules linked in:
  CPU: 1 PID: 2845 Comm: sched-pipe Tainted: G        W    3.14.0+ #256
  Hardware name: Intel Corporation Montevina platform/To be filled by O.E.M., BIOS AMVACRB1.86C.0066.B00.0805070703 05/07/2008
   0000000000000009 ffff880077233ab8 ffffffff81665a23 0000000000200005
   0000000000000000 ffff880077233af8 ffffffff8104732c 0000000000000046
   ffff88007467c800 0000000000000002 ffff88007a9cf2a0 0000000000000001
  Call Trace:
   [] dump_stack+0x4f/0x7c
   [] warn_slowpath_common+0x8c/0xc0
   [] warn_slowpath_null+0x1a/0x20
   [] perf_swevent_add+0x18d/0x1a0
   [] event_sched_in.isra.75+0x9e/0x1f0
   [] group_sched_in+0x6a/0x1f0
   [] ? sched_clock_local+0x25/0xa0
   [] ctx_sched_in+0x1f6/0x450
   [] perf_event_sched_in+0x6b/0xa0
   [] perf_event_context_sched_in+0x7b/0xc0
   [] __perf_event_task_sched_in+0x43e/0x460
   [] ? put_lock_stats.isra.18+0xe/0x30
   [] finish_task_switch+0xb8/0x100
   [] __schedule+0x30e/0xad0
   [] ? pipe_read+0x3e2/0x560
   [] ? preempt_schedule_irq+0x3e/0x70
   [] ? preempt_schedule_irq+0x3e/0x70
   [] preempt_schedule_irq+0x44/0x70
   [] retint_kernel+0x20/0x30
   [] ? lockdep_sys_exit+0x1a/0x90
   [] lockdep_sys_exit_thunk+0x35/0x67
   [] ? sysret_check+0x5/0x56

Fixing this by tracking the cpu hotplug state and displaying
the WARN only if current cpu is initialized properly.

Cc: Corey Ashford 
Cc: Frederic Weisbecker 
Cc: Ingo Molnar 
Cc: Paul Mackerras 
Cc: Arnaldo Carvalho de Melo 
Reported-by: Fengguang Wu 
Signed-off-by: Jiri Olsa 
Signed-off-by: Peter Zijlstra 
Link: http://lkml.kernel.org/r/1396861448-10097-1-git-send-email-jolsa@redhat.com
Signed-off-by: Thomas Gleixner 
Signed-off-by: Greg Kroah-Hartman

list: introduce list_next_entry() and list_prev_entry()

2014-05-31T04:52:14+00:00

[ Upstream commit 008208c6b26f21c2648c250a09c55e737c02c5f8 ]

Add two trivial helpers list_next_entry() and list_prev_entry(), they
can have a lot of users including list.h itself.  In fact the 1st one is
already defined in events/core.c and bnx2x_sp.c, so the patch simply
moves the definition to list.h.

Signed-off-by: Oleg Nesterov 
Cc: Eilon Greenstein 
Cc: Greg Kroah-Hartman 
Cc: Peter Zijlstra 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds 
Signed-off-by: Greg Kroah-Hartman

perf: Fix hotplug splat

2014-03-07T05:30:11+00:00

commit e3703f8cdfcf39c25c4338c3ad8e68891cca3731 upstream.

Drew Richardson reported that he could make the kernel go *boom* when hotplugging
while having perf events active.

It turned out that when you have a group event, the code in
__perf_event_exit_context() fails to remove the group siblings from
the context.

We then proceed with destroying and freeing the event, and when you
re-plug the CPU and try and add another event to that CPU, things go
*boom* because you've still got dead entries there.

Reported-by: Drew Richardson 
Signed-off-by: Peter Zijlstra 
Cc: Will Deacon 
Link: http://lkml.kernel.org/n/tip-k6v5wundvusvcseqj1si0oz0@git.kernel.org
Signed-off-by: Ingo Molnar 
Signed-off-by: Greg Kroah-Hartman

perf: Fix perf_lock_task_context() vs RCU

2013-07-25T21:07:43+00:00

commit 058ebd0eba3aff16b144eabf4510ed9510e1416e upstream.

Jiri managed to trigger this warning:

 [] ======================================================
 [] [ INFO: possible circular locking dependency detected ]
 [] 3.10.0+ #228 Tainted: G        W
 [] -------------------------------------------------------
 [] p/6613 is trying to acquire lock:
 []  (rcu_node_0){..-...}, at: [] rcu_read_unlock_special+0xa7/0x250
 []
 [] but task is already holding lock:
 []  (&ctx->lock){-.-...}, at: [] perf_lock_task_context+0xd9/0x2c0
 []
 [] which lock already depends on the new lock.
 []
 [] the existing dependency chain (in reverse order) is:
 []
 [] -> #4 (&ctx->lock){-.-...}:
 [] -> #3 (&rq->lock){-.-.-.}:
 [] -> #2 (&p->pi_lock){-.-.-.}:
 [] -> #1 (&rnp->nocb_gp_wq[1]){......}:
 [] -> #0 (rcu_node_0){..-...}:

Paul was quick to explain that due to preemptible RCU we cannot call
rcu_read_unlock() while holding scheduler (or nested) locks when part
of the read side critical section was preemptible.

Therefore solve it by making the entire RCU read side non-preemptible.

Also pull out the retry from under the non-preempt to play nice with RT.

Reported-by: Jiri Olsa 
Helped-out-by: Paul E. McKenney 
Signed-off-by: Peter Zijlstra 
Signed-off-by: Ingo Molnar 
Signed-off-by: Greg Kroah-Hartman

perf: Remove WARN_ON_ONCE() check in __perf_event_enable() for valid scenario

2013-07-25T21:07:42+00:00

commit 06f417968beac6e6b614e17b37d347aa6a6b1d30 upstream.

The '!ctx->is_active' check has a valid scenario, so
there's no need for the warning.

The reason is that there's a time window between the
'ctx->is_active' check in the perf_event_enable() function
and the __perf_event_enable() function having:

  - IRQs on
  - ctx->lock unlocked

where the task could be killed and 'ctx' deactivated by
perf_event_exit_task(), ending up with the warning below.

So remove the WARN_ON_ONCE() check and add comments to
explain it all.

This addresses the following warning reported by Vince Weaver:

[  324.983534] ------------[ cut here ]------------
[  324.984420] WARNING: at kernel/events/core.c:1953 __perf_event_enable+0x187/0x190()
[  324.984420] Modules linked in:
[  324.984420] CPU: 19 PID: 2715 Comm: nmi_bug_snb Not tainted 3.10.0+ #246
[  324.984420] Hardware name: Supermicro X8DTN/X8DTN, BIOS 4.6.3 01/08/2010
[  324.984420]  0000000000000009 ffff88043fce3ec8 ffffffff8160ea0b ffff88043fce3f00
[  324.984420]  ffffffff81080ff0 ffff8802314fdc00 ffff880231a8f800 ffff88043fcf7860
[  324.984420]  0000000000000286 ffff880231a8f800 ffff88043fce3f10 ffffffff8108103a
[  324.984420] Call Trace:
[  324.984420]    [] dump_stack+0x19/0x1b
[  324.984420]  [] warn_slowpath_common+0x70/0xa0
[  324.984420]  [] warn_slowpath_null+0x1a/0x20
[  324.984420]  [] __perf_event_enable+0x187/0x190
[  324.984420]  [] remote_function+0x40/0x50
[  324.984420]  [] generic_smp_call_function_single_interrupt+0xbe/0x130
[  324.984420]  [] smp_call_function_single_interrupt+0x27/0x40
[  324.984420]  [] call_function_single_interrupt+0x6f/0x80
[  324.984420]    [] ? _raw_spin_unlock_irqrestore+0x41/0x70
[  324.984420]  [] perf_event_exit_task+0x14d/0x210
[  324.984420]  [] ? switch_task_namespaces+0x24/0x60
[  324.984420]  [] do_exit+0x2b6/0xa40
[  324.984420]  [] ? _raw_spin_unlock_irq+0x2c/0x30
[  324.984420]  [] do_group_exit+0x49/0xc0
[  324.984420]  [] get_signal_to_deliver+0x254/0x620
[  324.984420]  [] do_signal+0x57/0x5a0
[  324.984420]  [] ? __do_page_fault+0x2a4/0x4e0
[  324.984420]  [] ? retint_restore_args+0xe/0xe
[  324.984420]  [] ? retint_signal+0x11/0x84
[  324.984420]  [] do_notify_resume+0x65/0x80
[  324.984420]  [] retint_signal+0x46/0x84
[  324.984420] ---[ end trace 442ec2f04db3771a ]---

Reported-by: Vince Weaver 
Signed-off-by: Jiri Olsa 
Suggested-by: Peter Zijlstra 
Cc: Corey Ashford 
Cc: Frederic Weisbecker 
Cc: Ingo Molnar 
Cc: Namhyung Kim 
Cc: Paul Mackerras 
Cc: Arnaldo Carvalho de Melo 
Signed-off-by: Peter Zijlstra 
Link: http://lkml.kernel.org/r/1373384651-6109-2-git-send-email-jolsa@redhat.com
Signed-off-by: Ingo Molnar 
Signed-off-by: Greg Kroah-Hartman