Skip to content

L
linux
Switch branch/tag
  1. 27 Feb, 2014 5 commits
    • Mark Rutland's avatar
      perf: Remove redundant PMU assignment · fdded676
      Mark Rutland authored 
      Currently perf_branch_stack_sched_in iterates over the set of pmus,
checks that each pmu has a flush_branch_stack callback, then overwrites
the pmu before calling the callback. This is either redundant or broken.

In systems with a single hw pmu, pmu == cpuctx->ctx.pmu, and thus the
assignment is redundant.

In systems with multiple hw pmus (i.e. multiple pmus with task_ctx_nr ==
perf_hw_context) the pmus share the same perf_cpu_context. Thus the
assignment can cause one of the pmus to flush its branch stack
repeatedly rather than causing each of the pmus to flush their branch
stacks. Worse still, if only some pmus have the callback the assignment
can result in a branch to NULL.

This patch removes the redundant assignment.
Signed-off-by: default avatarMark Rutland <mark.rutland@arm.com>
Acked-by: default avatarWill Deacon <will.deacon@arm.com>
Signed-off-by: default avatarPeter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Link: http://lkml.kernel.org/r/1392054264-23570-3-git-send-email-mark.rutland@arm.comSigned-off-by: default avatarIngo Molnar <mingo@kernel.org>
      fdded676
    • Mark Rutland's avatar
      perf: Fix prototype of find_pmu_context() · 9e317041
      Mark Rutland authored 
      For some reason find_pmu_context() is defined as returning void * rather
than a __percpu struct perf_cpu_context *. As all the requisite types are
defined in advance there's no reason to keep it that way.

This patch modifies the prototype of pmu_find_context to return a
__percpu struct perf_cpu_context *.
Signed-off-by: default avatarMark Rutland <mark.rutland@arm.com>
Signed-off-by: default avatarPeter Zijlstra <peterz@infradead.org>
Reviewed-by: default avatarDave Martin <Dave.Martin@arm.com>
Acked-by: default avatarWill Deacon <will.deacon@arm.com>
Link: http://lkml.kernel.org/r/1392054264-23570-2-git-send-email-mark.rutland@arm.comSigned-off-by: default avatarIngo Molnar <mingo@kernel.org>
      9e317041
    • Ingo Molnar's avatar
      Merge branch 'perf/urgent' into perf/core · ff5a7088
      Ingo Molnar authored 
      Merge the latest fixes before queueing up new changes.
Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
      ff5a7088
    • Peter Zijlstra's avatar
      perf: Fix hotplug splat · e3703f8c
      Peter Zijlstra authored 
      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: default avatarDrew Richardson <drew.richardson@arm.com>
Signed-off-by: default avatarPeter Zijlstra <peterz@infradead.org>
Cc: Will Deacon <will.deacon@arm.com>
Cc: <stable@vger.kernel.org>
Link: http://lkml.kernel.org/n/tip-k6v5wundvusvcseqj1si0oz0@git.kernel.orgSigned-off-by: default avatarIngo Molnar <mingo@kernel.org>
      e3703f8c
    • Peter Zijlstra's avatar
      perf/x86: Fix event scheduling · 26e61e89
      Peter Zijlstra authored 
      Vince "Super Tester" Weaver reported a new round of syscall fuzzing (Trinity) failures,
with perf WARN_ON()s triggering. He also provided traces of the failures.

This is I think the relevant bit:

	>    pec_1076_warn-2804  [000] d...   147.926153: x86_pmu_disable: x86_pmu_disable
	>    pec_1076_warn-2804  [000] d...   147.926153: x86_pmu_state: Events: {
	>    pec_1076_warn-2804  [000] d...   147.926156: x86_pmu_state:   0: state: .R config: ffffffffffffffff (          (null))
	>    pec_1076_warn-2804  [000] d...   147.926158: x86_pmu_state:   33: state: AR config: 0 (ffff88011ac99800)
	>    pec_1076_warn-2804  [000] d...   147.926159: x86_pmu_state: }
	>    pec_1076_warn-2804  [000] d...   147.926160: x86_pmu_state: n_events: 1, n_added: 0, n_txn: 1
	>    pec_1076_warn-2804  [000] d...   147.926161: x86_pmu_state: Assignment: {
	>    pec_1076_warn-2804  [000] d...   147.926162: x86_pmu_state:   0->33 tag: 1 config: 0 (ffff88011ac99800)
	>    pec_1076_warn-2804  [000] d...   147.926163: x86_pmu_state: }
	>    pec_1076_warn-2804  [000] d...   147.926166: collect_events: Adding event: 1 (ffff880119ec8800)

So we add the insn:p event (fd[23]).

At this point we should have:

  n_events = 2, n_added = 1, n_txn = 1

	>    pec_1076_warn-2804  [000] d...   147.926170: collect_events: Adding event: 0 (ffff8800c9e01800)
	>    pec_1076_warn-2804  [000] d...   147.926172: collect_events: Adding event: 4 (ffff8800cbab2c00)

We try and add the {BP,cycles,br_insn} group (fd[3], fd[4], fd[15]).
These events are 0:cycles and 4:br_insn, the BP event isn't x86_pmu so
that's not visible.

	group_sched_in()
	  pmu->start_txn() /* nop - BP pmu */
	  event_sched_in()
	     event->pmu->add()

So here we should end up with:

  0: n_events = 3, n_added = 2, n_txn = 2
  4: n_events = 4, n_added = 3, n_txn = 3

But seeing the below state on x86_pmu_enable(), the must have failed,
because the 0 and 4 events aren't there anymore.

Looking at group_sched_in(), since the BP is the leader, its
event_sched_in() must have succeeded, for otherwise we would not have
seen the sibling adds.

But since neither 0 or 4 are in the below state; their event_sched_in()
must have failed; but I don't see why, the complete state: 0,0,1:p,4
fits perfectly fine on a core2.

However, since we try and schedule 4 it means the 0 event must have
succeeded!  Therefore the 4 event must have failed, its failure will
have put group_sched_in() into the fail path, which will call:

	event_sched_out()
	  event->pmu->del()

on 0 and the BP event.

Now x86_pmu_del() will reduce n_events; but it will not reduce n_added;
giving what we see below:

 n_event = 2, n_added = 2, n_txn = 2

	>    pec_1076_warn-2804  [000] d...   147.926177: x86_pmu_enable: x86_pmu_enable
	>    pec_1076_warn-2804  [000] d...   147.926177: x86_pmu_state: Events: {
	>    pec_1076_warn-2804  [000] d...   147.926179: x86_pmu_state:   0: state: .R config: ffffffffffffffff (          (null))
	>    pec_1076_warn-2804  [000] d...   147.926181: x86_pmu_state:   33: state: AR config: 0 (ffff88011ac99800)
	>    pec_1076_warn-2804  [000] d...   147.926182: x86_pmu_state: }
	>    pec_1076_warn-2804  [000] d...   147.926184: x86_pmu_state: n_events: 2, n_added: 2, n_txn: 2
	>    pec_1076_warn-2804  [000] d...   147.926184: x86_pmu_state: Assignment: {
	>    pec_1076_warn-2804  [000] d...   147.926186: x86_pmu_state:   0->33 tag: 1 config: 0 (ffff88011ac99800)
	>    pec_1076_warn-2804  [000] d...   147.926188: x86_pmu_state:   1->0 tag: 1 config: 1 (ffff880119ec8800)
	>    pec_1076_warn-2804  [000] d...   147.926188: x86_pmu_state: }
	>    pec_1076_warn-2804  [000] d...   147.926190: x86_pmu_enable: S0: hwc->idx: 33, hwc->last_cpu: 0, hwc->last_tag: 1 hwc->state: 0

So the problem is that x86_pmu_del(), when called from a
group_sched_in() that fails (for whatever reason), and without x86_pmu
TXN support (because the leader is !x86_pmu), will corrupt the n_added
state.
Reported-and-Tested-by: default avatarVince Weaver <vincent.weaver@maine.edu>
Signed-off-by: default avatarPeter Zijlstra <peterz@infradead.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Stephane Eranian <eranian@google.com>
Cc: Dave Jones <davej@redhat.com>
Cc: <stable@vger.kernel.org>
Link: http://lkml.kernel.org/r/20140221150312.GF3104@twins.programming.kicks-ass.netSigned-off-by: default avatarIngo Molnar <mingo@kernel.org>
      26e61e89
  3. 25 Feb, 2014 16 commits
  5. 24 Feb, 2014 7 commits
  7. 23 Feb, 2014 12 commits
GitLab Nexedi Edition | About GitLab | About Nexedi | 沪ICP备2021021310号-2 | 沪ICP备2021021310号-7