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perf/core: Robustify the perf_cgroup_from_task() RCU checks 

This patch reinforces the lockdep checks performed by
perf_cgroup_from_tsk() by passing the perf_event_context
whenever possible. It is okay to not hold the RCU read lock
when we know we hold the ctx->lock. This patch makes sure this
property holds.

In some functions, such as perf_cgroup_sched_in(), we do not
pass the context because we are sure we are holding the RCU
read lock.

Signed-off-by: Stephane Eranian <eranian@google.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vince Weaver <vincent.weaver@maine.edu>
Cc: edumazet@google.com
Link: http://lkml.kernel.org/r/1447322404-10920-3-git-send-email-eranian@google.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Stephane Eranian 2015-11-12 11:00:04 +01:00 committed by Ingo Molnar
parent ddaaf4e291
commit 614e4c4ebc
3 changed files with 18 additions and 10 deletions
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2
arch/x86/kernel/cpu/perf_event_intel_cqm.c
View File

@ -298,7 +298,7 @@ static bool __match_event(struct perf_event *a, struct perf_event *b)
static inline struct perf_cgroup *event_to_cgroup(struct perf_event *event)
{
if (event->attach_state & PERF_ATTACH_TASK)
return perf_cgroup_from_task(event->hw.target);
return perf_cgroup_from_task(event->hw.target, event->ctx);
return event->cgrp;
}

6
include/linux/perf_event.h
View File

@ -697,9 +697,11 @@ struct perf_cgroup {
* if there is no cgroup event for the current CPU context.
*/
static inline struct perf_cgroup *
perf_cgroup_from_task(struct task_struct *task)
perf_cgroup_from_task(struct task_struct *task, struct perf_event_context *ctx)
{
return container_of(task_css(task, perf_event_cgrp_id),
return container_of(task_css_check(task, perf_event_cgrp_id,
ctx ? lockdep_is_held(&ctx->lock)
: true),
struct perf_cgroup, css);
}
#endif /* CONFIG_CGROUP_PERF */

20
kernel/events/core.c
View File

@ -435,7 +435,7 @@ static inline void update_cgrp_time_from_event(struct perf_event *event)
if (!is_cgroup_event(event))
return;
cgrp = perf_cgroup_from_task(current);
cgrp = perf_cgroup_from_task(current, event->ctx);
/*
* Do not update time when cgroup is not active
*/
@ -458,7 +458,7 @@ perf_cgroup_set_timestamp(struct task_struct *task,
if (!task || !ctx->nr_cgroups)
return;
cgrp = perf_cgroup_from_task(task);
cgrp = perf_cgroup_from_task(task, ctx);
info = this_cpu_ptr(cgrp->info);
info->timestamp = ctx->timestamp;
}
@ -521,8 +521,10 @@ static void perf_cgroup_switch(struct task_struct *task, int mode)
* set cgrp before ctxsw in to allow
* event_filter_match() to not have to pass
* task around
* we pass the cpuctx->ctx to perf_cgroup_from_task()
* because cgorup events are only per-cpu
*/
cpuctx->cgrp = perf_cgroup_from_task(task);
cpuctx->cgrp = perf_cgroup_from_task(task, &cpuctx->ctx);
cpu_ctx_sched_in(cpuctx, EVENT_ALL, task);
}
perf_pmu_enable(cpuctx->ctx.pmu);
@ -542,15 +544,17 @@ static inline void perf_cgroup_sched_out(struct task_struct *task,
rcu_read_lock();
/*
* we come here when we know perf_cgroup_events > 0
* we do not need to pass the ctx here because we know
* we are holding the rcu lock
*/
cgrp1 = perf_cgroup_from_task(task);
cgrp1 = perf_cgroup_from_task(task, NULL);
/*
* next is NULL when called from perf_event_enable_on_exec()
* that will systematically cause a cgroup_switch()
*/
if (next)
cgrp2 = perf_cgroup_from_task(next);
cgrp2 = perf_cgroup_from_task(next, NULL);
/*
* only schedule out current cgroup events if we know
@ -572,11 +576,13 @@ static inline void perf_cgroup_sched_in(struct task_struct *prev,
rcu_read_lock();
/*
* we come here when we know perf_cgroup_events > 0
* we do not need to pass the ctx here because we know
* we are holding the rcu lock
*/
cgrp1 = perf_cgroup_from_task(task);
cgrp1 = perf_cgroup_from_task(task, NULL);
/* prev can never be NULL */
cgrp2 = perf_cgroup_from_task(prev);
cgrp2 = perf_cgroup_from_task(prev, NULL);
/*
* only need to schedule in cgroup events if we are changing