Commit-ID: 3ed769bdb2a2484fd7f9f7f3047413053aacbe21 Gitweb: http://git.kernel.org/tip/3ed769bdb2a2484fd7f9f7f3047413053aacbe21 Author: Dmitry Vyukov <[email protected]> AuthorDate: Fri, 18 Sep 2015 15:54:23 +0200 Committer: Thomas Gleixner <[email protected]> CommitDate: Tue, 22 Sep 2015 15:43:18 +0200
timers: Fix data race in timer_stats_account_timer() timer_stats_account_timer() reads timer->start_site, then checks it for NULL and then re-reads it again, while timer_stats_timer_clear_start_info() can concurrently reset timer->start_site to NULL. This should not lead to crashes, but can double number of entries in timer stats as start_site is used during comparison, the doubled entries will have unuseful NULL start_site. Read timer->start_site only once in timer_stats_account_timer(). The data race was found with KernelThreadSanitizer (KTSAN). Signed-off-by: Dmitry Vyukov <[email protected]> Cc: [email protected] Cc: [email protected] Cc: [email protected] Cc: [email protected] Cc: [email protected] Link: http://lkml.kernel.org/r/[email protected] Signed-off-by: Thomas Gleixner <[email protected]> --- kernel/time/timer.c | 11 +++++++++-- 1 file changed, 9 insertions(+), 2 deletions(-) diff --git a/kernel/time/timer.c b/kernel/time/timer.c index 84190f0..d3f5e92 100644 --- a/kernel/time/timer.c +++ b/kernel/time/timer.c @@ -461,10 +461,17 @@ void __timer_stats_timer_set_start_info(struct timer_list *timer, void *addr) static void timer_stats_account_timer(struct timer_list *timer) { - if (likely(!timer->start_site)) + void *site; + + /* + * start_site can be concurrently reset by + * timer_stats_timer_clear_start_info() + */ + site = READ_ONCE(timer->start_site); + if (likely(!site)) return; - timer_stats_update_stats(timer, timer->start_pid, timer->start_site, + timer_stats_update_stats(timer, timer->start_pid, site, timer->function, timer->start_comm, timer->flags); } -- 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/
