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authorLinus Torvalds <torvalds@linux-foundation.org>2023-11-19 13:26:42 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2023-11-19 13:26:42 -0800
commitc8b3443cbde91251970893fe4d5dc465c1a76a7e (patch)
tree388d65f4ba8e9116cec01424e3108b6fdf726aa9 /kernel
parent037266a5f7239ead1530266f7d7af153d2a867fa (diff)
parent889c58b3155ff4c8e8671c95daef63d6fabbb6b1 (diff)
downloadlwn-c8b3443cbde91251970893fe4d5dc465c1a76a7e.tar.gz
lwn-c8b3443cbde91251970893fe4d5dc465c1a76a7e.zip
Merge tag 'perf_urgent_for_v6.7_rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull perf fix from Borislav Petkov: - Make sure the context refcount is transferred too when migrating perf events * tag 'perf_urgent_for_v6.7_rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: perf/core: Fix cpuctx refcounting
Diffstat (limited to 'kernel')
-rw-r--r--kernel/events/core.c17
1 files changed, 17 insertions, 0 deletions
diff --git a/kernel/events/core.c b/kernel/events/core.c
index 683dc086ef10..b704d83a28b2 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -4828,6 +4828,11 @@ find_get_pmu_context(struct pmu *pmu, struct perf_event_context *ctx,
void *task_ctx_data = NULL;
if (!ctx->task) {
+ /*
+ * perf_pmu_migrate_context() / __perf_pmu_install_event()
+ * relies on the fact that find_get_pmu_context() cannot fail
+ * for CPU contexts.
+ */
struct perf_cpu_pmu_context *cpc;
cpc = per_cpu_ptr(pmu->cpu_pmu_context, event->cpu);
@@ -12889,6 +12894,9 @@ static void __perf_pmu_install_event(struct pmu *pmu,
int cpu, struct perf_event *event)
{
struct perf_event_pmu_context *epc;
+ struct perf_event_context *old_ctx = event->ctx;
+
+ get_ctx(ctx); /* normally find_get_context() */
event->cpu = cpu;
epc = find_get_pmu_context(pmu, ctx, event);
@@ -12897,6 +12905,11 @@ static void __perf_pmu_install_event(struct pmu *pmu,
if (event->state >= PERF_EVENT_STATE_OFF)
event->state = PERF_EVENT_STATE_INACTIVE;
perf_install_in_context(ctx, event, cpu);
+
+ /*
+ * Now that event->ctx is updated and visible, put the old ctx.
+ */
+ put_ctx(old_ctx);
}
static void __perf_pmu_install(struct perf_event_context *ctx,
@@ -12935,6 +12948,10 @@ void perf_pmu_migrate_context(struct pmu *pmu, int src_cpu, int dst_cpu)
struct perf_event_context *src_ctx, *dst_ctx;
LIST_HEAD(events);
+ /*
+ * Since per-cpu context is persistent, no need to grab an extra
+ * reference.
+ */
src_ctx = &per_cpu_ptr(&perf_cpu_context, src_cpu)->ctx;
dst_ctx = &per_cpu_ptr(&perf_cpu_context, dst_cpu)->ctx;