Messages in this thread Patch in this message | | | From | Jiri Olsa <> | Subject | [PATCH 1/1] perf: Prevent race in PERF_SAMPLE_READ group format sample output | Date | Wed, 25 Jun 2014 20:44:35 +0200 |
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From: Jiri Olsa <jolsa@redhat.com>
While iterating siblings in perf_output_read_group we could race with addition and removal of sibling in perf_group_attach and perf_group_detach respective.
While in perf_output_read_group we are under active context, so the only sibling_list modification could come via IPI in: perf_install_in_context or perf_remove_from_context
Disable interrupts before iterating siblings to prevent this race.
Cc: Arnaldo Carvalho de Melo <acme@kernel.org> Cc: Corey Ashford <cjashfor@linux.vnet.ibm.com> Cc: Frederic Weisbecker <fweisbec@gmail.com> Cc: Ingo Molnar <mingo@kernel.org> Cc: Paul Mackerras <paulus@samba.org> Cc: Peter Zijlstra <a.p.zijlstra@chello.nl> Signed-off-by: Jiri Olsa <jolsa@kernel.org> --- kernel/events/core.c | 11 +++++++++++ 1 file changed, 11 insertions(+)
diff --git a/kernel/events/core.c b/kernel/events/core.c index a33d9a2b..66649d3 100644 --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -4509,6 +4509,7 @@ static void perf_output_read_group(struct perf_output_handle *handle, { struct perf_event *leader = event->group_leader, *sub; u64 read_format = event->attr.read_format; + unsigned long flags; u64 values[5]; int n = 0; @@ -4529,6 +4530,15 @@ static void perf_output_read_group(struct perf_output_handle *handle, __output_copy(handle, values, n * sizeof(u64)); + /* + * We are now under active context, so the only sibling_list + * modification could come via IPI in: + * perf_install_in_context and perf_remove_from_context + * + * Disable interrupts to prevent this race. + */ + local_irq_save(flags); + list_for_each_entry(sub, &leader->sibling_list, group_entry) { n = 0; @@ -4542,6 +4552,7 @@ static void perf_output_read_group(struct perf_output_handle *handle, __output_copy(handle, values, n * sizeof(u64)); } + local_irq_restore(flags); } #define PERF_FORMAT_TOTAL_TIMES (PERF_FORMAT_TOTAL_TIME_ENABLED|\ -- 1.8.3.1
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