There has been some discussion on lkml about a function that would
either down a semaphore or else abort if it couldn't get the semaphore
in a certain amount of time. Something along the lines of:
down_timeout(struct semaphore *sem, long timeout);
Does something like this exist? Does anyone have a working
implementation? Does anyone see anything obviously wrong with the
following version (that I loosely based on one by Rupert Eibauer)?
semaphore.h:
extern int __down_timeout(struct semaphore * sem, unsigned int timeout);
/* "timeout" is the number of jiffies to wait.
* Returns -ETIME if timeout period expires.
*/
static inline int down_timeout(struct semaphore * sem, unsigned int timeout)
{
int ret = down_trylock(sem);
if (!ret)
ret = __down_timeout(sem, timeout);
return ret;
}
kernel/timer.c
int __down_timeout(struct semaphore * sem, int timeout)
{
int ret;
unsigned long expire;
struct timer_list timer;
expire = jiffies + timeout;
init_timer(&timer);
timer.expires = expire;
timer.data = (unsigned long) current;
timer.function = process_timeout;
add_timer(&timer);
ret = down_interruptible(sema);
if (ret && (jiffies > expire))
ret = -ETIME;
else
del_timer_sync(&timer);
return ret;
}
Thanks,
Chris
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