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Commit 3eac4aba authored by Kevin Hilman's avatar Kevin Hilman Committed by Linus Torvalds
Browse files

rwsem generic spinlock: use IRQ save/restore spinlocks 



rwsems can be used with IRQs disabled, particularily in early boot
before IRQs are enabled.  Currently the spin_unlock_irq() usage in the
slow-patch will unconditionally enable interrupts and cause problems
since interrupts are not yet initialized or enabled.

This patch uses save/restore versions of IRQ spinlocks in the slowpath
to ensure interrupts are not unintentionally disabled.

Signed-off-by: default avatarKevin Hilman <khilman@deeprootsystems.com>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 04287f97

lib/rwsem-spinlock.c

+8 −6
Original line number Original line Diff line number Diff line
@@ -143,13 +143,14 @@ void __sched __down_read(struct rw_semaphore *sem) 
{

{

	struct rwsem_waiter waiter;

	struct rwsem_waiter waiter;

	struct task_struct *tsk;

	struct task_struct *tsk;

	unsigned long flags;





	spin_lock_irq(&sem->wait_lock);

	spin_lock_irqsave(&sem->wait_lock, flags);





	if (sem->activity >= 0 && list_empty(&sem->wait_list)) {

	if (sem->activity >= 0 && list_empty(&sem->wait_list)) {

		/* granted */

		/* granted */

		sem->activity++;

		sem->activity++;

		spin_unlock_irq(&sem->wait_lock);

		spin_unlock_irqrestore(&sem->wait_lock, flags);

		goto out;

		goto out;

	}

	}
@@ -164,7 +165,7 @@ void __sched __down_read(struct rw_semaphore *sem) 
	list_add_tail(&waiter.list, &sem->wait_list);

	list_add_tail(&waiter.list, &sem->wait_list);





	/* we don't need to touch the semaphore struct anymore */

	/* we don't need to touch the semaphore struct anymore */

	spin_unlock_irq(&sem->wait_lock);

	spin_unlock_irqrestore(&sem->wait_lock, flags);





	/* wait to be given the lock */

	/* wait to be given the lock */

	for (;;) {

	for (;;) {
@@ -209,13 +210,14 @@ void __sched __down_write_nested(struct rw_semaphore *sem, int subclass) 
{

{

	struct rwsem_waiter waiter;

	struct rwsem_waiter waiter;

	struct task_struct *tsk;

	struct task_struct *tsk;

	unsigned long flags;





	spin_lock_irq(&sem->wait_lock);

	spin_lock_irqsave(&sem->wait_lock, flags);





	if (sem->activity == 0 && list_empty(&sem->wait_list)) {

	if (sem->activity == 0 && list_empty(&sem->wait_list)) {

		/* granted */

		/* granted */

		sem->activity = -1;

		sem->activity = -1;

		spin_unlock_irq(&sem->wait_lock);

		spin_unlock_irqrestore(&sem->wait_lock, flags);

		goto out;

		goto out;

	}

	}
@@ -230,7 +232,7 @@ void __sched __down_write_nested(struct rw_semaphore *sem, int subclass) 
	list_add_tail(&waiter.list, &sem->wait_list);

	list_add_tail(&waiter.list, &sem->wait_list);





	/* we don't need to touch the semaphore struct anymore */

	/* we don't need to touch the semaphore struct anymore */

	spin_unlock_irq(&sem->wait_lock);

	spin_unlock_irqrestore(&sem->wait_lock, flags);





	/* wait to be given the lock */

	/* wait to be given the lock */

	for (;;) {

	for (;;) {