Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753366AbcDZST3 (ORCPT ); Tue, 26 Apr 2016 14:19:29 -0400 Received: from youngberry.canonical.com ([91.189.89.112]:56615 "EHLO youngberry.canonical.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753317AbcDZSTX (ORCPT ); Tue, 26 Apr 2016 14:19:23 -0400 From: Kamal Mostafa To: linux-kernel@vger.kernel.org, stable@vger.kernel.org, kernel-team@lists.ubuntu.com Cc: Heiko Carstens , Kamal Mostafa Subject: [PATCH 4.2.y-ckt 85/93] s390/spinlock: avoid yield to non existent cpu Date: Tue, 26 Apr 2016 11:17:25 -0700 Message-Id: <1461694653-29506-86-git-send-email-kamal@canonical.com> X-Mailer: git-send-email 2.7.4 In-Reply-To: <1461694653-29506-1-git-send-email-kamal@canonical.com> References: <1461694653-29506-1-git-send-email-kamal@canonical.com> X-Extended-Stable: 4.2 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1581 Lines: 43 4.2.8-ckt9 -stable review patch. If anyone has any objections, please let me know. ---8<------------------------------------------------------------ From: Heiko Carstens commit 8497695243f70fd19ed6cf28b63584f1b608b5f9 upstream. arch_spin_lock_wait_flags() checks if a spinlock is not held before trying a compare and swap instruction. If the lock is unlocked it tries the compare and swap instruction, however if a different cpu grabbed the lock in the meantime the instruction will fail as expected. Subsequently the arch_spin_lock_wait_flags() incorrectly tries to figure out if the cpu that holds the lock is running. However it is using the wrong cpu number for this (-1) and then will also yield the current cpu to the wrong cpu. Fix this by adding a missing continue statement. Fixes: 470ada6b1a1d ("s390/spinlock: refactor arch_spin_lock_wait[_flags]") Signed-off-by: Heiko Carstens Acked-by: Martin Schwidefsky Signed-off-by: Kamal Mostafa --- arch/s390/lib/spinlock.c | 1 + 1 file changed, 1 insertion(+) diff --git a/arch/s390/lib/spinlock.c b/arch/s390/lib/spinlock.c index d6c9991..27f2651 100644 --- a/arch/s390/lib/spinlock.c +++ b/arch/s390/lib/spinlock.c @@ -90,6 +90,7 @@ void arch_spin_lock_wait_flags(arch_spinlock_t *lp, unsigned long flags) if (_raw_compare_and_swap(&lp->lock, 0, cpu)) return; local_irq_restore(flags); + continue; } /* Check if the lock owner is running. */ if (!smp_vcpu_scheduled(~owner)) { -- 2.7.4