Messages in this thread | | | Date | Wed, 9 Aug 2017 15:43:09 +0100 | From | Mel Gorman <> | Subject | Re: [PATCH] futex: Remove unnecessary warning from get_futex_key |
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On Wed, Aug 09, 2017 at 03:05:19PM +0100, Mark Rutland wrote: > > diff --git a/kernel/futex.c b/kernel/futex.c > > index 16dbe4c93895..f50b434756c1 100644 > > --- a/kernel/futex.c > > +++ b/kernel/futex.c > > @@ -670,13 +670,14 @@ get_futex_key(u32 __user *uaddr, int fshared, union futex_key *key, int rw) > > * this reference was taken by ihold under the page lock > > * pinning the inode in place so i_lock was unnecessary. The > > * only way for this check to fail is if the inode was > > - * truncated in parallel so warn for now if this happens. > > + * truncated in parallel which is almost certainly an > > + * application bug. In such a case, just retry. > > * > > * We are not calling into get_futex_key_refs() in file-backed > > * cases, therefore a successful atomic_inc return below will > > * guarantee that get_futex_key() will still imply smp_mb(); (B). > > */ > > - if (WARN_ON_ONCE(!atomic_inc_not_zero(&inode->i_count))) { > > + if (!atomic_inc_not_zero(&inode->i_count)) { > > I applied the same diff yesterday, and haven't seen anything go wrong > with my test case and/or with Syzkaller running, so FWIW: > > Tested-by: Mark Rutland <mark.rutland@arm.com> > > Thanks for putting this together! >
No problem. FWIW, I had the test case running for 12 hours in a loop as well and other than having to adjust the number of threads doing futex() to trigger the warning without the patch, I observed no other problems. If Thomas is happy, I hope this can be merged for 4.13 (or picked up directly by Linus if he feels like it). Even if it's delayed, I'll resubmit to -stable manually if the "Cc: stable" gets stripped along the way.
-- Mel Gorman SUSE Labs
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