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authorLinus Torvalds <torvalds@linux-foundation.org>2014-10-13 18:06:09 +0400
committerLinus Torvalds <torvalds@linux-foundation.org>2014-10-13 18:06:09 +0400
commitebf546cc5391b9a8a17c1196b05b4357ef0138a2 (patch)
tree8ee8a9c1ef57710a07290228883db7ca742bf835
parent9d9420f1209a1facea7110d549ac695f5aeeb503 (diff)
parent9c2b9d30e28559a78c9e431cdd7f2c6bf5a9ee67 (diff)
downloadlinux-ebf546cc5391b9a8a17c1196b05b4357ef0138a2.tar.xz
Merge branch 'perf-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull perf fixes from Ingo Molnar: "Two leftover fixes from the v3.17 cycle - these will be forwarded to stable as well, if they prove problem-free in wider testing as well" [ Side note: the "fix perf bug in fork()" fix had also come in through Andrew's patch-bomb - Linus ] * 'perf-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: perf: Fix perf bug in fork() perf: Fix unclone_ctx() vs. locking
-rw-r--r--kernel/events/core.c54
1 files changed, 31 insertions, 23 deletions
diff --git a/kernel/events/core.c b/kernel/events/core.c
index 385f11d94105..094df8c0742d 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -906,13 +906,23 @@ static void put_ctx(struct perf_event_context *ctx)
}
}
-static void unclone_ctx(struct perf_event_context *ctx)
+/*
+ * This must be done under the ctx->lock, such as to serialize against
+ * context_equiv(), therefore we cannot call put_ctx() since that might end up
+ * calling scheduler related locks and ctx->lock nests inside those.
+ */
+static __must_check struct perf_event_context *
+unclone_ctx(struct perf_event_context *ctx)
{
- if (ctx->parent_ctx) {
- put_ctx(ctx->parent_ctx);
+ struct perf_event_context *parent_ctx = ctx->parent_ctx;
+
+ lockdep_assert_held(&ctx->lock);
+
+ if (parent_ctx)
ctx->parent_ctx = NULL;
- }
ctx->generation++;
+
+ return parent_ctx;
}
static u32 perf_event_pid(struct perf_event *event, struct task_struct *p)
@@ -2259,6 +2269,9 @@ static void ctx_sched_out(struct perf_event_context *ctx,
static int context_equiv(struct perf_event_context *ctx1,
struct perf_event_context *ctx2)
{
+ lockdep_assert_held(&ctx1->lock);
+ lockdep_assert_held(&ctx2->lock);
+
/* Pinning disables the swap optimization */
if (ctx1->pin_count || ctx2->pin_count)
return 0;
@@ -2992,6 +3005,7 @@ static int event_enable_on_exec(struct perf_event *event,
*/
static void perf_event_enable_on_exec(struct perf_event_context *ctx)
{
+ struct perf_event_context *clone_ctx = NULL;
struct perf_event *event;
unsigned long flags;
int enabled = 0;
@@ -3023,7 +3037,7 @@ static void perf_event_enable_on_exec(struct perf_event_context *ctx)
* Unclone this context if we enabled any event.
*/
if (enabled)
- unclone_ctx(ctx);
+ clone_ctx = unclone_ctx(ctx);
raw_spin_unlock(&ctx->lock);
@@ -3033,6 +3047,9 @@ static void perf_event_enable_on_exec(struct perf_event_context *ctx)
perf_event_context_sched_in(ctx, ctx->task);
out:
local_irq_restore(flags);
+
+ if (clone_ctx)
+ put_ctx(clone_ctx);
}
void perf_event_exec(void)
@@ -3185,7 +3202,7 @@ errout:
static struct perf_event_context *
find_get_context(struct pmu *pmu, struct task_struct *task, int cpu)
{
- struct perf_event_context *ctx;
+ struct perf_event_context *ctx, *clone_ctx = NULL;
struct perf_cpu_context *cpuctx;
unsigned long flags;
int ctxn, err;
@@ -3219,9 +3236,12 @@ find_get_context(struct pmu *pmu, struct task_struct *task, int cpu)
retry:
ctx = perf_lock_task_context(task, ctxn, &flags);
if (ctx) {
- unclone_ctx(ctx);
+ clone_ctx = unclone_ctx(ctx);
++ctx->pin_count;
raw_spin_unlock_irqrestore(&ctx->lock, flags);
+
+ if (clone_ctx)
+ put_ctx(clone_ctx);
} else {
ctx = alloc_perf_context(pmu, task);
err = -ENOMEM;
@@ -7646,7 +7666,7 @@ __perf_event_exit_task(struct perf_event *child_event,
static void perf_event_exit_task_context(struct task_struct *child, int ctxn)
{
struct perf_event *child_event, *next;
- struct perf_event_context *child_ctx, *parent_ctx;
+ struct perf_event_context *child_ctx, *clone_ctx = NULL;
unsigned long flags;
if (likely(!child->perf_event_ctxp[ctxn])) {
@@ -7673,28 +7693,16 @@ static void perf_event_exit_task_context(struct task_struct *child, int ctxn)
child->perf_event_ctxp[ctxn] = NULL;
/*
- * In order to avoid freeing: child_ctx->parent_ctx->task
- * under perf_event_context::lock, grab another reference.
- */
- parent_ctx = child_ctx->parent_ctx;
- if (parent_ctx)
- get_ctx(parent_ctx);
-
- /*
* If this context is a clone; unclone it so it can't get
* swapped to another process while we're removing all
* the events from it.
*/
- unclone_ctx(child_ctx);
+ clone_ctx = unclone_ctx(child_ctx);
update_context_time(child_ctx);
raw_spin_unlock_irqrestore(&child_ctx->lock, flags);
- /*
- * Now that we no longer hold perf_event_context::lock, drop
- * our extra child_ctx->parent_ctx reference.
- */
- if (parent_ctx)
- put_ctx(parent_ctx);
+ if (clone_ctx)
+ put_ctx(clone_ctx);
/*
* Report the task dead after unscheduling the events so that we