Attachment 153476 Details for Bug 198014 – Patch to restore owner after umtx_pi_claim fails

[patch] Patch to restore owner after umtx_pi_claim fails

umtx_pi_claim_restore.patch (text/plain), 1.11 KB, created by eric on 2015-02-24 21:26:03 UTC

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Creator: eric

Created: 2015-02-24 21:26:03 UTC

Size: 1.11 KB

patch

obsolete

>commit 987cd93bb90597d81e39ca6c968550bf129b8747
>Author: evangyzen <eric_van_gyzen@dell.com>
>Date:   Tue Feb 24 14:25:08 2015 -0500
>
>    When locking a PI mutex, restore original owner on a rare error path
>    
>    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.
>
>diff --git a/sys/kern/kern_umtx.c b/sys/kern/kern_umtx.c
>index cc7c16d..11f312a 100644
>--- a/sys/kern/kern_umtx.c
>+++ b/sys/kern/kern_umtx.c
>@@ -1741,6 +1741,17 @@ do_lock_pi(struct thread *td, struct umutex *m, uint32_t flags,
> 				error = umtx_pi_claim(pi, td);
> 				umtxq_unbusy(&uq->uq_key);
> 				umtxq_unlock(&uq->uq_key);
>+				if (error) {
>+					/*
>+					 * 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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