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Commit 2e4006b3 authored by Gerald Schaefer's avatar Gerald Schaefer Committed by Martin Schwidefsky
Browse files

s390/spinlock: fix system hang with spin_retry <= 0 



On LPAR, when spin_retry is set to <= 0, arch_spin_lock_wait() and
arch_spin_lock_wait_flags() may end up in a while(1) loop w/o doing
any compare and swap operation. To fix this, use do/while instead of
for loop.

Signed-off-by: default avatarGerald Schaefer <gerald.schaefer@de.ibm.com>
Signed-off-by: default avatarMartin Schwidefsky <schwidefsky@de.ibm.com>
parent f1a85820

arch/s390/lib/spinlock.c

+8 −6
Original line number Original line Diff line number Diff line
@@ -26,19 +26,20 @@ __setup("spin_retry=", spin_retry_setup); 




void arch_spin_lock_wait(arch_spinlock_t *lp)

void arch_spin_lock_wait(arch_spinlock_t *lp)

{

{

	int count = spin_retry;

	unsigned int cpu = SPINLOCK_LOCKVAL;

	unsigned int cpu = SPINLOCK_LOCKVAL;

	unsigned int owner;

	unsigned int owner;

	int count;





	while (1) {

	while (1) {

		owner = lp->lock;

		owner = lp->lock;

		if (!owner || smp_vcpu_scheduled(~owner)) {

		if (!owner || smp_vcpu_scheduled(~owner)) {

			for (count = spin_retry; count > 0; count--) {

			count = spin_retry;

			do {

				if (arch_spin_is_locked(lp))

				if (arch_spin_is_locked(lp))

					continue;

					continue;

				if (_raw_compare_and_swap(&lp->lock, 0, cpu))

				if (_raw_compare_and_swap(&lp->lock, 0, cpu))

					return;

					return;

			}

			} while (count-- > 0);

			if (MACHINE_IS_LPAR)

			if (MACHINE_IS_LPAR)

				continue;

				continue;

		}

		}
@@ -53,22 +54,23 @@ EXPORT_SYMBOL(arch_spin_lock_wait); 




void arch_spin_lock_wait_flags(arch_spinlock_t *lp, unsigned long flags)

void arch_spin_lock_wait_flags(arch_spinlock_t *lp, unsigned long flags)

{

{

	int count = spin_retry;

	unsigned int cpu = SPINLOCK_LOCKVAL;

	unsigned int cpu = SPINLOCK_LOCKVAL;

	unsigned int owner;

	unsigned int owner;

	int count;





	local_irq_restore(flags);

	local_irq_restore(flags);

	while (1) {

	while (1) {

		owner = lp->lock;

		owner = lp->lock;

		if (!owner || smp_vcpu_scheduled(~owner)) {

		if (!owner || smp_vcpu_scheduled(~owner)) {

			for (count = spin_retry; count > 0; count--) {

			count = spin_retry;

			do {

				if (arch_spin_is_locked(lp))

				if (arch_spin_is_locked(lp))

					continue;

					continue;

				local_irq_disable();

				local_irq_disable();

				if (_raw_compare_and_swap(&lp->lock, 0, cpu))

				if (_raw_compare_and_swap(&lp->lock, 0, cpu))

					return;

					return;

				local_irq_restore(flags);

				local_irq_restore(flags);

			}

			} while (count-- > 0);

			if (MACHINE_IS_LPAR)

			if (MACHINE_IS_LPAR)

				continue;

				continue;

		}

		}