Commit 84976952 authored Apr 13, 2016 by Heiko Carstens Committed by Martin Schwidefsky Apr 15, 2016

s390/spinlock: avoid yield to non existent cpu



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: 470ada6b ("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>

parent 1378a683

arch/s390/lib/spinlock.c

+1 −0

Original line number	Diff line number	Diff line
		@@ -105,6 +105,7 @@ 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 (first_diag && cpu_is_preempted(~owner)) {

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