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authorJiri Olsa <jolsa@kernel.org>2014-08-01 14:33:02 +0200
committerIngo Molnar <mingo@kernel.org>2014-08-13 07:51:04 +0200
commitfadfe7be6e50de7f03913833b33c56cd8fb66bac (patch)
treec1a4212e5509ac5390f1a6297dcafcebde12edd6 /kernel/events
parentf86977620ee4635f26befcf436700493a38ce002 (diff)
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perf: Add queued work to remove orphaned child events
In cases when the owner task exits before the workload and the workload made some forks, all the events stay in until the last workload process exits. Thats' because each child event holds parent reference. We want to release all children events once the parent is gone, because at that time there's no process to read them anyway, so they're just eating resources. This removal races with process exit, which removes all events and fork, which clone events. To be clear of those two, adding work queue to remove orphaned child for context in case such event is detected. Using delayed work queue (with delay == 1), because we queue this work under perf scheduler callbacks. Normal work queue tries to wake up the queue process, which deadlocks on rq->lock in this place. Also preventing clones from abandoned parent event. Signed-off-by: Jiri Olsa <jolsa@kernel.org> Signed-off-by: Peter Zijlstra <peterz@infradead.org> Cc: Arnaldo Carvalho de Melo <acme@kernel.org> Cc: Corey Ashford <cjashfor@linux.vnet.ibm.com> Cc: Frederic Weisbecker <fweisbec@gmail.com> Cc: Mark Rutland <mark.rutland@arm.com> Cc: Paul Mackerras <paulus@samba.org> Cc: Arnaldo Carvalho de Melo <acme@kernel.org> Cc: Corey Ashford <cjashfor@linux.vnet.ibm.com> Cc: Frederic Weisbecker <fweisbec@gmail.com> Cc: Mark Rutland <mark.rutland@arm.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Link: http://lkml.kernel.org/r/1406896382-18404-4-git-send-email-jolsa@kernel.org Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'kernel/events')
-rw-r--r--kernel/events/core.c87
1 files changed, 86 insertions, 1 deletions
diff --git a/kernel/events/core.c b/kernel/events/core.c
index bbb3ca22f07c..a25460559b4f 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -46,6 +46,8 @@
#include <asm/irq_regs.h>
+static struct workqueue_struct *perf_wq;
+
struct remote_function_call {
struct task_struct *p;
int (*func)(void *info);
@@ -1381,6 +1383,45 @@ out:
perf_event__header_size(tmp);
}
+/*
+ * User event without the task.
+ */
+static bool is_orphaned_event(struct perf_event *event)
+{
+ return event && !is_kernel_event(event) && !event->owner;
+}
+
+/*
+ * Event has a parent but parent's task finished and it's
+ * alive only because of children holding refference.
+ */
+static bool is_orphaned_child(struct perf_event *event)
+{
+ return is_orphaned_event(event->parent);
+}
+
+static void orphans_remove_work(struct work_struct *work);
+
+static void schedule_orphans_remove(struct perf_event_context *ctx)
+{
+ if (!ctx->task || ctx->orphans_remove_sched || !perf_wq)
+ return;
+
+ if (queue_delayed_work(perf_wq, &ctx->orphans_remove, 1)) {
+ get_ctx(ctx);
+ ctx->orphans_remove_sched = true;
+ }
+}
+
+static int __init perf_workqueue_init(void)
+{
+ perf_wq = create_singlethread_workqueue("perf");
+ WARN(!perf_wq, "failed to create perf workqueue\n");
+ return perf_wq ? 0 : -1;
+}
+
+core_initcall(perf_workqueue_init);
+
static inline int
event_filter_match(struct perf_event *event)
{
@@ -1430,6 +1471,9 @@ event_sched_out(struct perf_event *event,
if (event->attr.exclusive || !cpuctx->active_oncpu)
cpuctx->exclusive = 0;
+ if (is_orphaned_child(event))
+ schedule_orphans_remove(ctx);
+
perf_pmu_enable(event->pmu);
}
@@ -1732,6 +1776,9 @@ event_sched_in(struct perf_event *event,
if (event->attr.exclusive)
cpuctx->exclusive = 1;
+ if (is_orphaned_child(event))
+ schedule_orphans_remove(ctx);
+
out:
perf_pmu_enable(event->pmu);
@@ -3074,6 +3121,7 @@ static void __perf_event_init_context(struct perf_event_context *ctx)
INIT_LIST_HEAD(&ctx->flexible_groups);
INIT_LIST_HEAD(&ctx->event_list);
atomic_set(&ctx->refcount, 1);
+ INIT_DELAYED_WORK(&ctx->orphans_remove, orphans_remove_work);
}
static struct perf_event_context *
@@ -3405,6 +3453,42 @@ static int perf_release(struct inode *inode, struct file *file)
return 0;
}
+/*
+ * Remove all orphanes events from the context.
+ */
+static void orphans_remove_work(struct work_struct *work)
+{
+ struct perf_event_context *ctx;
+ struct perf_event *event, *tmp;
+
+ ctx = container_of(work, struct perf_event_context,
+ orphans_remove.work);
+
+ mutex_lock(&ctx->mutex);
+ list_for_each_entry_safe(event, tmp, &ctx->event_list, event_entry) {
+ struct perf_event *parent_event = event->parent;
+
+ if (!is_orphaned_child(event))
+ continue;
+
+ perf_remove_from_context(event, true);
+
+ mutex_lock(&parent_event->child_mutex);
+ list_del_init(&event->child_list);
+ mutex_unlock(&parent_event->child_mutex);
+
+ free_event(event);
+ put_event(parent_event);
+ }
+
+ raw_spin_lock_irq(&ctx->lock);
+ ctx->orphans_remove_sched = false;
+ raw_spin_unlock_irq(&ctx->lock);
+ mutex_unlock(&ctx->mutex);
+
+ put_ctx(ctx);
+}
+
u64 perf_event_read_value(struct perf_event *event, u64 *enabled, u64 *running)
{
struct perf_event *child;
@@ -7709,7 +7793,8 @@ inherit_event(struct perf_event *parent_event,
if (IS_ERR(child_event))
return child_event;
- if (!atomic_long_inc_not_zero(&parent_event->refcount)) {
+ if (is_orphaned_event(parent_event) ||
+ !atomic_long_inc_not_zero(&parent_event->refcount)) {
free_event(child_event);
return NULL;
}