Messages in this thread | | | Subject | Re: [locks] 6d390e4b5d: will-it-scale.per_process_ops -96.6% regression | From | Jeff Layton <> | Date | Thu, 19 Mar 2020 13:51:59 -0400 |
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On Mon, 2020-03-16 at 10:26 -0700, 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? > > 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! >
Thanks for all the help with this.
Yangerkun gave me his Reviewed-by and I sent you the most recent version of the patch yesterday (cc'ing the relevant mailing lists). I left you as author as the original patch was yours.
Let me know if you'd prefer I send a pull request instead.
Cheers, -- Jeff Layton <jlayton@kernel.org>
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