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authorLinus Torvalds <torvalds@linux-foundation.org>2013-07-13 15:35:47 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2013-07-13 15:35:47 -0700
commit560ae37178b12e3bd37626f7b1e0b29c503ea558 (patch)
tree24105534940152466aa331fb76a9438c85e634b5 /kernel
parent4fa109b13042868de84bedc70ea9b8337b502cf9 (diff)
parentbaf64b85445546a38b44052d71782dfe7531e350 (diff)
downloadlinux-560ae37178b12e3bd37626f7b1e0b29c503ea558.tar.bz2
Merge branch 'perf-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull perf fixes from Thomas Gleixner: - fix for do_div() abuse on x86 - locking fix in perf core - a pile of (build) fixes and cleanups in perf tools * 'perf-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (27 commits) perf/x86: Fix incorrect use of do_div() in NMI warning perf: Fix perf_lock_task_context() vs RCU perf: Remove WARN_ON_ONCE() check in __perf_event_enable() for valid scenario perf: Clone child context from parent context pmu perf script: Fix broken include in Context.xs perf tools: Fix -ldw/-lelf link test when static linking perf tools: Revert regression in configuration of Python support perf tools: Fix perf version generation perf stat: Fix per-socket output bug for uncore events perf symbols: Fix vdso list searching perf evsel: Fix missing increment in sample parsing perf tools: Update symbol_conf.nr_events when processing attribute events perf tools: Fix new_term() missing free on error path perf tools: Fix parse_events_terms() segfault on error path perf evsel: Fix count parameter to read call in event_format__new perf tools: fix a typo of a Power7 event name perf tools: Fix -x/--exclude-other option for report command perf evlist: Enhance perf_evlist__start_workload() perf record: Remove -f/--force option perf record: Remove -A/--append option ...
Diffstat (limited to 'kernel')
-rw-r--r--kernel/events/core.c28
1 files changed, 25 insertions, 3 deletions
diff --git a/kernel/events/core.c b/kernel/events/core.c
index 1833bc5a84a7..eba8fb5834ae 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -947,8 +947,18 @@ perf_lock_task_context(struct task_struct *task, int ctxn, unsigned long *flags)
{
struct perf_event_context *ctx;
- rcu_read_lock();
retry:
+ /*
+ * One of the few rules of preemptible RCU is that one cannot do
+ * rcu_read_unlock() while holding a scheduler (or nested) lock when
+ * part of the read side critical section was preemptible -- see
+ * rcu_read_unlock_special().
+ *
+ * Since ctx->lock nests under rq->lock we must ensure the entire read
+ * side critical section is non-preemptible.
+ */
+ preempt_disable();
+ rcu_read_lock();
ctx = rcu_dereference(task->perf_event_ctxp[ctxn]);
if (ctx) {
/*
@@ -964,6 +974,8 @@ retry:
raw_spin_lock_irqsave(&ctx->lock, *flags);
if (ctx != rcu_dereference(task->perf_event_ctxp[ctxn])) {
raw_spin_unlock_irqrestore(&ctx->lock, *flags);
+ rcu_read_unlock();
+ preempt_enable();
goto retry;
}
@@ -973,6 +985,7 @@ retry:
}
}
rcu_read_unlock();
+ preempt_enable();
return ctx;
}
@@ -1950,7 +1963,16 @@ static int __perf_event_enable(void *info)
struct perf_cpu_context *cpuctx = __get_cpu_context(ctx);
int err;
- if (WARN_ON_ONCE(!ctx->is_active))
+ /*
+ * There's a time window between 'ctx->is_active' check
+ * in perf_event_enable function and this place having:
+ * - IRQs on
+ * - ctx->lock unlocked
+ *
+ * where the task could be killed and 'ctx' deactivated
+ * by perf_event_exit_task.
+ */
+ if (!ctx->is_active)
return -EINVAL;
raw_spin_lock(&ctx->lock);
@@ -7465,7 +7487,7 @@ inherit_task_group(struct perf_event *event, struct task_struct *parent,
* child.
*/
- child_ctx = alloc_perf_context(event->pmu, child);
+ child_ctx = alloc_perf_context(parent_ctx->pmu, child);
if (!child_ctx)
return -ENOMEM;