-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 On 08/15/2014 12:49 PM, Oleg Nesterov wrote:
> Just in case... Yes, sure, "seqlock_t stats_lock" is more scalable. > Just I do not know it's worth the trouble. If we don't know whether it is worth the trouble, it is probably best to stick to a well-known generic locking algorithm, instead of brewing our own and trying to maintain it. I have fixed the other locking issue you pointed out, Oleg. Now to see if this change to cputime_adjust does the trick :) +++ b/kernel/sched/cputime.c @@ -605,9 +605,12 @@ static void cputime_adjust(struct task_cputime *curr, * If the tick based count grows faster than the scheduler one, * the result of the scaling may go backward. * Let's enforce monotonicity. + * Atomic exchange protects against concurrent cputime_adjust. */ - - prev->stime = max(prev->stime, stime); - - prev->utime = max(prev->utime, utime); + while (stime > (rtime = ACCESS_ONCE(prev->stime))) + cmpxchg(&prev->stime, rtime, stime); + while (utime > (rtime = ACCESS_ONCE(prev->utime))) + cmpxchg(&prev->utime, rtime, utime); -----BEGIN PGP SIGNATURE----- Version: GnuPG v1 iQEcBAEBAgAGBQJT7kJ4AAoJEM553pKExN6Do/oH/2lA5X/CrVuhOLBK1sVq3kRh gGiOTT9pDQZH1wwafVNHKWaro3T/s9GNqemgvgt4UiKbjFeYkaOycHp1cuntJj8j Wk8zNnWBOuGqqcSxzk1Duco3CByxshLNXxuYJfpdkdEXPqRyvURAOL58pxSybZzh E6lT747ntFJu3GIbfC6Ta3q58pWLpVrhWlvonhSaqat6tOvlzo4MKiJxz3SbT6i0 cCpmQ5p/JoQ5+IUEbTOZYbE2bK2y5tSrMggAFwKWLB3/0zJm1h4+2Q/5PenCX59X VDFmaOJLkNxGcVXg8x87itvqzfq/LkvDtwl9tTJmA5ccG37MPvM3803XF5OWVo0= =aKES -----END PGP SIGNATURE----- -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/