Date: Wed, 25 Feb 2015 16:17:17 +0000 (UTC) From: Konstantin Belousov <kib@FreeBSD.org> To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: svn commit: r279283 - head/sys/kern Message-ID: <201502251617.t1PGHHXZ087098@svn.freebsd.org>
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Author: kib Date: Wed Feb 25 16:17:16 2015 New Revision: 279283 URL: https://svnweb.freebsd.org/changeset/base/279283 Log: When failing to claim ownership of a umtx_pi, restore the umutex owner to its previous, unowned state. This avoids compounding an existing problem of inconsistent ownership. Submitted by: Eric van Gyzen <eric_van_gyzen@dell.com> Obtained from: Dell Inc. PR: 198914 MFC after: 1 week Modified: head/sys/kern/kern_umtx.c Modified: head/sys/kern/kern_umtx.c ============================================================================== --- head/sys/kern/kern_umtx.c Wed Feb 25 16:12:56 2015 (r279282) +++ head/sys/kern/kern_umtx.c Wed Feb 25 16:17:16 2015 (r279283) @@ -1741,6 +1741,17 @@ do_lock_pi(struct thread *td, struct umu error = umtx_pi_claim(pi, td); umtxq_unbusy(&uq->uq_key); umtxq_unlock(&uq->uq_key); + if (error != 0) { + /* + * Since we're going to return an + * error, restore the m_owner to its + * previous, unowned state to avoid + * compounding the problem. + */ + (void)casuword32(&m->m_owner, + id | UMUTEX_CONTESTED, + UMUTEX_CONTESTED); + } break; }
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