| From | 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 |
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4.2.8-ckt9 -stable review patch. If anyone has any objections, please let me know.
---8<------------------------------------------------------------
From: Heiko Carstens <heiko.carstens@de.ibm.com>
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 <heiko.carstens@de.ibm.com> Acked-by: Martin Schwidefsky <schwidefsky@de.ibm.com> Signed-off-by: Kamal Mostafa <kamal@canonical.com> --- 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
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