lk/linux-kernel-test
1
0
Fork 0
Code Issues Pull Requests Releases Wiki Activity

Add down_timeout and change ACPI to use it

Browse Source 
ACPI currently emulates a timeout for semaphores with calls to
down_trylock and sleep.  This produces horrible behaviour in terms of
fairness and excessive wakeups.  Now that we have a unified semaphore
implementation, adding a real down_trylock is almost trivial.

Signed-off-by: Matthew Wilcox <willy@linux.intel.com>
This commit is contained in:
Matthew Wilcox
2008-03-14 13:43:13 -04:00
committed by Matthew Wilcox
parent f06d968658
commit f1241c87a1
3 changed files with 62 additions and 75 deletions
Download Patch File Download Diff File Expand all files Collapse all files

42
kernel/semaphore.c
View File

@@ -35,6 +35,7 @@
static noinline void __down(struct semaphore *sem);
static noinline int __down_interruptible(struct semaphore *sem);
static noinline int __down_killable(struct semaphore *sem);
static noinline int __down_timeout(struct semaphore *sem, long jiffies);
static noinline void __up(struct semaphore *sem);
void down(struct semaphore *sem)
@@ -104,6 +105,20 @@ int down_trylock(struct semaphore *sem)
}
EXPORT_SYMBOL(down_trylock);
int down_timeout(struct semaphore *sem, long jiffies)
{
unsigned long flags;
int result = 0;
spin_lock_irqsave(&sem->lock, flags);
if (unlikely(sem->count-- <= 0))
result = __down_timeout(sem, jiffies);
spin_unlock_irqrestore(&sem->lock, flags);
return result;
}
EXPORT_SYMBOL(down_timeout);
void up(struct semaphore *sem)
{
unsigned long flags;
@@ -142,10 +157,12 @@ static noinline void __sched __up_down_common(struct semaphore *sem)
}
/*
* Because this function is inlined, the 'state' parameter will be constant,
* and thus optimised away by the compiler.
* Because this function is inlined, the 'state' parameter will be
* constant, and thus optimised away by the compiler. Likewise the
* 'timeout' parameter for the cases without timeouts.
*/
static inline int __sched __down_common(struct semaphore *sem, long state)
static inline int __sched __down_common(struct semaphore *sem, long state,
long timeout)
{
int result = 0;
struct task_struct *task = current;
@@ -160,14 +177,20 @@ static inline int __sched __down_common(struct semaphore *sem, long state)
goto interrupted;
if (state == TASK_KILLABLE && fatal_signal_pending(task))
goto interrupted;
if (timeout <= 0)
goto timed_out;
__set_task_state(task, state);
spin_unlock_irq(&sem->lock);
schedule();
timeout = schedule_timeout(timeout);
spin_lock_irq(&sem->lock);
if (waiter.up)
goto woken;
}
timed_out:
list_del(&waiter.list);
result = -ETIME;
goto woken;
interrupted:
list_del(&waiter.list);
result = -EINTR;
@@ -187,17 +210,22 @@ static inline int __sched __down_common(struct semaphore *sem, long state)
static noinline void __sched __down(struct semaphore *sem)
{
__down_common(sem, TASK_UNINTERRUPTIBLE);
__down_common(sem, TASK_UNINTERRUPTIBLE, MAX_SCHEDULE_TIMEOUT);
}
static noinline int __sched __down_interruptible(struct semaphore *sem)
{
return __down_common(sem, TASK_INTERRUPTIBLE);
return __down_common(sem, TASK_INTERRUPTIBLE, MAX_SCHEDULE_TIMEOUT);
}
static noinline int __sched __down_killable(struct semaphore *sem)
{
return __down_common(sem, TASK_KILLABLE);
return __down_common(sem, TASK_KILLABLE, MAX_SCHEDULE_TIMEOUT);
}
static noinline int __sched __down_timeout(struct semaphore *sem, long jiffies)
{
return __down_common(sem, TASK_UNINTERRUPTIBLE, jiffies);
}
static noinline void __sched __up(struct semaphore *sem)