Date: Tue, 18 Aug 2015 10:15:10 +0000 (UTC) From: Julien Charbon <jch@FreeBSD.org> To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: svn commit: r286880 - head/sys/kern Message-ID: <201508181015.t7IAFAex055889@repo.freebsd.org>
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Author: jch Date: Tue Aug 18 10:15:09 2015 New Revision: 286880 URL: https://svnweb.freebsd.org/changeset/base/286880 Log: callout_stop() should return 0 (fail) when the callout is currently being serviced and indeed unstoppable. A scenario to reproduce this case is: - the callout is being serviced and at same time, - callout_reset() is called on this callout that sets the CALLOUT_PENDING flag and at same time, - callout_stop() is called on this callout and returns 1 (success) even if the callout is indeed currently running and unstoppable. This issue was caught up while making r284245 (D2763) workaround, and was discussed at BSDCan 2015. Once applied the r284245 workaround is not needed anymore and will be reverted. Differential Revision: https://reviews.freebsd.org/D3078 Reviewed by: jhb Sponsored by: Verisign, Inc. Modified: head/sys/kern/kern_timeout.c Modified: head/sys/kern/kern_timeout.c ============================================================================== --- head/sys/kern/kern_timeout.c Tue Aug 18 10:07:03 2015 (r286879) +++ head/sys/kern/kern_timeout.c Tue Aug 18 10:15:09 2015 (r286880) @@ -1150,7 +1150,7 @@ _callout_stop_safe(struct callout *c, in struct callout_cpu *cc, *old_cc; struct lock_class *class; int direct, sq_locked, use_lock; - int not_on_a_list; + int not_on_a_list, not_running; if (safe) WITNESS_WARN(WARN_GIANTOK | WARN_SLEEPOK, c->c_lock, @@ -1378,8 +1378,15 @@ again: } } callout_cc_del(c, cc); + + /* + * If we are asked to stop a callout which is currently in progress + * and indeed impossible to stop then return 0. + */ + not_running = !(cc_exec_curr(cc, direct) == c); + CC_UNLOCK(cc); - return (1); + return (not_running); } void
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