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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: Kevin Hilman <khilman@deeprootsystems.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Kevin Hilman 2010-04-07 11:52:46 -07:00 committed by Linus Torvalds
parent 04287f975e
commit 3eac4abaa6
1 changed files with 8 additions and 6 deletions
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14
lib/rwsem-spinlock.c
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@ -143,13 +143,14 @@ void __sched __down_read(struct rw_semaphore *sem)
{
struct rwsem_waiter waiter;
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)) {
/* granted */
sem->activity++;
spin_unlock_irq(&sem->wait_lock);
spin_unlock_irqrestore(&sem->wait_lock, flags);
goto out;
}
@ -164,7 +165,7 @@ void __sched __down_read(struct rw_semaphore *sem)
list_add_tail(&waiter.list, &sem->wait_list);
/* 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 */
for (;;) {
@ -209,13 +210,14 @@ void __sched __down_write_nested(struct rw_semaphore *sem, int subclass)
{
struct rwsem_waiter waiter;
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)) {
/* granted */
sem->activity = -1;
spin_unlock_irq(&sem->wait_lock);
spin_unlock_irqrestore(&sem->wait_lock, flags);
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);
/* 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 */
for (;;) {