Messages in this thread | | | From | "Moore, Robert" <> | Subject | RE: down_timeout | Date | Thu, 26 Apr 2001 09:27:56 -0700 |
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I see this as the kind of function that should be implemented within the semaphore interface itself. Very simple - Just wake me up when either 1) I get the semaphore, or 2) I timed out.
A single implementation saves everyone from attempting to implement this over and over and over.
Bob
-----Original Message----- From: Ingo Oeser [mailto:ingo.oeser@informatik.tu-chemnitz.de] Sent: Wednesday, April 25, 2001 4:49 PM To: Grover, Andrew Cc: 'linux-kernel@vger.kernel.org'; Moore, Robert Subject: Re: down_timeout
On Wed, Apr 25, 2001 at 04:21:22PM -0700, Grover, Andrew wrote: > It seems like we need to implement down_timeout (and > down_timeout_interruptible) to fully flesh out the semaphore implementation. > It is difficult and inefficient to emulate this using wrapper functions, as > far as I can see. > > Seems like this is a fairly standard interface to have for OS semaphores. We > have a prototype implementation, and could contribute this, if desired. > > Thoughts?
Sure you can't implement this via waitqueues? semaphores use them internally anyway.
I use this for interrupt or polling based waiting:
/* IO polling waits */ /* Timeout after this amount of jiffies */ #define IO_POLL_TIMEOUT (HZ) /* Split timeout while polling into chunks of that many jiffies */ #define IO_POLL_SPLIT 2
/* generic interrupt based wait with timeouts! */ #define __wait_event_timeout_int(wq, condition, timeout, ret) \ do { \ struct wait_queue __wait; \ signed long __expire=timeout; \ __wait.task=current; \ add_wait_queue(wq, &__wait); \ for (;;) { \ current->state=TASK_UNINTERRUPTIBLE; \ mb(); \ if (condition) break; \ __expire=schedule_timeout(__expire); \ if (__expire == 0) { \ ret=-ETIMEDOUT; \ break; \ } \ } \ current->state = TASK_RUNNING; \ remove_wait_queue(wq, &__wait); \ } while (0)
/* polling wait, if we shouldn't use interrupts for this */ #define __wait_event_timeout_poll(wq, condition, timeout, ret) \ do { \ unsigned int __tries=0; \ unsigned int __maxtry=timeout / IO_POLL_SPLIT; \ do { \ schedule_timeout(IO_POLL_SPLIT); \ if (condition) \ break; \ } while (++__tries < __maxtry); \ if (__tries == __maxtry && !condition) \ ret=-ETIMEDOUT; \ } while (0) #ifdef INTS_ARE_CHEAP #define __wait_event_timeout(wq, condition, timeout, ret) \ __wait_event_timeout_int(wq, condition, timeout, ret) #else /* INTS_ARE_CHEAP */ #define __wait_event_timeout(wq, condition, timeout, ret) \ __wait_event_timeout_poll(wq, condition, timeout, ret) #endif /* INTS_ARE_CHEAP */
#define wait_event_timeout(wq, condition, timeout, ret) \ do { \ if (condition) \ break; \ __wait_event_timeout(wq, condition, timeout, ret); \ } while (0)
What about that?
Use it just as you use wait_event() but check for -ETIMEDOUT as value in ret.
Regards
Ingo Oeser -- 10.+11.03.2001 - 3. Chemnitzer LinuxTag <http://www.tu-chemnitz.de/linux/tag> <<<<<<<<<<<< been there and had much fun >>>>>>>>>>>>
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