From: Jiri Olsa <[email protected]> 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 <[email protected]> Cc: Corey Ashford <[email protected]> Cc: Frederic Weisbecker <[email protected]> Cc: Ingo Molnar <[email protected]> Cc: Paul Mackerras <[email protected]> Cc: Peter Zijlstra <[email protected]> Signed-off-by: Jiri Olsa <[email protected]> --- 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 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
