Messages in this thread | | | Subject | Re: [locks] 6d390e4b5d: will-it-scale.per_process_ops -96.6% regression | From | yangerkun <> | Date | Tue, 17 Mar 2020 09:41:27 +0800 |
| |
On 2020/3/17 1:26, Linus Torvalds wrote: > On Mon, Mar 16, 2020 at 4:07 AM Jeff Layton <jlayton@kernel.org> wrote: >> >> >> + /* >> + * If fl_blocker is NULL, it won't be set again as this thread "owns" >> + * the lock and is the only one that might try to claim the lock. >> + * Because fl_blocker is explicitly set last during a delete, it's >> + * safe to locklessly test to see if it's NULL. If it is, then we know >> + * that no new locks can be inserted into its fl_blocked_requests list, >> + * and we can therefore avoid doing anything further as long as that >> + * list is empty. >> + */ >> + if (!smp_load_acquire(&waiter->fl_blocker) && >> + list_empty(&waiter->fl_blocked_requests)) >> + return status; > > Ack. This looks sane to me now. > > yangerkun - how did you find the original problem?\
While try to fix CVE-2019-19769, add some log in __locks_wake_up_blocks help me to rebuild the problem soon. This help me to discern the problem soon.
> > Would you mind using whatever stress test that caused commit > 6d390e4b5d48 ("locks: fix a potential use-after-free problem when > wakeup a waiter") with this patch? And if you did it analytically, > you're a champ and should look at this patch too!
I will try to understand this patch, and if it's looks good to me, will do the performance test!
Thanks
| |