From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Tony Thompson , Will Deacon , Russell King , Li Zefan Subject: [PATCH 3.10 87/97] ARM: 7749/1: spinlock: retry trylock operation if strex fails on free lock Date: Tue, 4 Mar 2014 12:04:40 -0800 Message-Id: <20140304200348.875416170@linuxfoundation.org> In-Reply-To: <20140304200345.895517495@linuxfoundation.org> References: <20140304200345.895517495@linuxfoundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: 3.10-stable review patch. If anyone has any objections, please let me know. ------------------ From: Will Deacon commit 15e7e5c1ebf556cd620c9b091e121091ac760f6d upstream. An exclusive store instruction may fail for reasons other than lock contention (e.g. a cache eviction during the critical section) so, in line with other architectures using similar exclusive instructions (alpha, mips, powerpc), retry the trylock operation if the lock appears to be free but the strex reported failure. Reported-by: Tony Thompson Signed-off-by: Will Deacon Signed-off-by: Russell King Cc: Li Zefan Signed-off-by: Greg Kroah-Hartman --- arch/arm/include/asm/spinlock.h | 23 +++++++++++++---------- 1 file changed, 13 insertions(+), 10 deletions(-) --- a/arch/arm/include/asm/spinlock.h +++ b/arch/arm/include/asm/spinlock.h @@ -97,19 +97,22 @@ static inline void arch_spin_lock(arch_s static inline int arch_spin_trylock(arch_spinlock_t *lock) { - unsigned long tmp; + unsigned long contended, res; u32 slock; - __asm__ __volatile__( -" ldrex %0, [%2]\n" -" subs %1, %0, %0, ror #16\n" -" addeq %0, %0, %3\n" -" strexeq %1, %0, [%2]" - : "=&r" (slock), "=&r" (tmp) - : "r" (&lock->slock), "I" (1 << TICKET_SHIFT) - : "cc"); + do { + __asm__ __volatile__( + " ldrex %0, [%3]\n" + " mov %2, #0\n" + " subs %1, %0, %0, ror #16\n" + " addeq %0, %0, %4\n" + " strexeq %2, %0, [%3]" + : "=&r" (slock), "=&r" (contended), "=r" (res) + : "r" (&lock->slock), "I" (1 << TICKET_SHIFT) + : "cc"); + } while (res); - if (tmp == 0) { + if (!contended) { smp_mb(); return 1; } else {