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| author | Peter Zijlstra <peterz@infradead.org> | 2023-06-09 12:34:46 +0200 |
|---|---|---|
| committer | Ingo Molnar <mingo@kernel.org> | 2023-11-15 04:18:31 +0100 |
| commit | 889c58b3155ff4c8e8671c95daef63d6fabbb6b1 (patch) | |
| tree | b3e5e03a84f667fcae07cab2b64a26afaff2ab1e /kernel | |
| parent | Linux 6.7-rc1 (diff) | |
| download | linux-889c58b3155ff4c8e8671c95daef63d6fabbb6b1.tar.xz linux-889c58b3155ff4c8e8671c95daef63d6fabbb6b1.zip | |
perf/core: Fix cpuctx refcounting
Audit of the refcounting turned up that perf_pmu_migrate_context()
fails to migrate the ctx refcount.
Fixes: bd2756811766 ("perf: Rewrite core context handling")
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lkml.kernel.org/r/20230612093539.085862001@infradead.org
Cc: <stable@vger.kernel.org>
Diffstat (limited to 'kernel')
| -rw-r--r-- | kernel/events/core.c | 17 |
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; |