s390/spinlock: avoid yield to non existent cpu

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: Ben Hutchings <ben@decadent.org.uk>

diff --git a/arch/s390/lib/spinlock.c b/arch/s390/lib/spinlock.c
index 5b0e445bc3f39930317bafc745c76c674874bf0e..9beb186b3af59a6b551915d51821c202507ebead 100644 (file)
--- a/arch/s390/lib/spinlock.c
+++ b/arch/s390/lib/spinlock.c
@@ -75,6 +75,7 @@ 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)) {