Re: [Semaphore API] down_interruptible_timeout
On 15/06/2015 18:56, Thomas Gleixner wrote: > On Mon, 15 Jun 2015, Mason wrote: > >> A) process-context kernel thread fills a FIFO and calls down(_empty); >> B) ISR handles the FIFO-empty interrupt with up(_empty); >> >> However, in case something goes wrong and the interrupt never fires, >> I don't want the process to be stuck in an uninterruptible sleep. >> >> Perhaps I can set a tiny timeout (e.g. 10 µs) and not worry about >> the interruptible part for such a small duration? (Hmm, __down_common >> calls schedule_timeout, which is jiffies-based. I don't think there >> is a hrtimers flavor. So µs timeouts would be off the table?) >> >> Or I could use the interruptible version, and let the user kill the >> operation if necessary. > > Use a completion. Thanks for the pointer. I will also read the following LKML thread. http://thread.gmane.org/gmane.linux.kernel/664514 Regards. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [Semaphore API] down_interruptible_timeout
On 15/06/2015 18:56, Thomas Gleixner wrote: On Mon, 15 Jun 2015, Mason wrote: A) process-context kernel thread fills a FIFO and calls down(fifo_empty); B) ISR handles the FIFO-empty interrupt with up(fifo_empty); However, in case something goes wrong and the interrupt never fires, I don't want the process to be stuck in an uninterruptible sleep. Perhaps I can set a tiny timeout (e.g. 10 µs) and not worry about the interruptible part for such a small duration? (Hmm, __down_common calls schedule_timeout, which is jiffies-based. I don't think there is a hrtimers flavor. So µs timeouts would be off the table?) Or I could use the interruptible version, and let the user kill the operation if necessary. Use a completion. Thanks for the pointer. I will also read the following LKML thread. http://thread.gmane.org/gmane.linux.kernel/664514 Regards. -- To unsubscribe from this list: send the line unsubscribe linux-kernel in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [Semaphore API] down_interruptible_timeout
On Mon, 15 Jun 2015, Mason wrote: > A) process-context kernel thread fills a FIFO and calls down(_empty); > B) ISR handles the FIFO-empty interrupt with up(_empty); > > However, in case something goes wrong and the interrupt never fires, > I don't want the process to be stuck in an uninterruptible sleep. > > Perhaps I can set a tiny timeout (e.g. 10 µs) and not worry about > the interruptible part for such a small duration? (Hmm, __down_common > calls schedule_timeout, which is jiffies-based. I don't think there > is a hrtimers flavor. So µs timeouts would be off the table?) > > Or I could use the interruptible version, and let the user kill the > operation if necessary. Use a completion. Thanks, tglx
[Semaphore API] down_interruptible_timeout
Hello, The semaphore API provides several flavors of the down primitive: down, down_interruptible, down_killable, down_trylock, down_timeout As far as I can tell, they all call __down_common (except down_trylock, which returns 1 where the others would sleep). I was looking for a version 1) with a timeout 2) that could be interrupted e.g. down_interruptible_timeout, but it doesn't exist. It seems __down_common(sem, TASK_INTERRUPTIBLE, timeout); would work as expected, no? Do you know why it is not offered? (Maybe there is a better way to achieve the same thing?) [POST SCRIPTUM EDIT] I found this 2007 discussion: http://thread.gmane.org/gmane.linux.kernel/498034 At the time, Andrew said "Nobody else has needed to invent new locking infrastructure to do such things and I'd prefer not to do so now." I suppose this is still true :-) [/EDIT] My use-case is pretty simple: A) process-context kernel thread fills a FIFO and calls down(_empty); B) ISR handles the FIFO-empty interrupt with up(_empty); However, in case something goes wrong and the interrupt never fires, I don't want the process to be stuck in an uninterruptible sleep. Perhaps I can set a tiny timeout (e.g. 10 µs) and not worry about the interruptible part for such a small duration? (Hmm, __down_common calls schedule_timeout, which is jiffies-based. I don't think there is a hrtimers flavor. So µs timeouts would be off the table?) Or I could use the interruptible version, and let the user kill the operation if necessary. I'd like to hear your comments and suggestions. Regards. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [Semaphore API] down_interruptible_timeout
On Mon, 15 Jun 2015, Mason wrote: A) process-context kernel thread fills a FIFO and calls down(fifo_empty); B) ISR handles the FIFO-empty interrupt with up(fifo_empty); However, in case something goes wrong and the interrupt never fires, I don't want the process to be stuck in an uninterruptible sleep. Perhaps I can set a tiny timeout (e.g. 10 µs) and not worry about the interruptible part for such a small duration? (Hmm, __down_common calls schedule_timeout, which is jiffies-based. I don't think there is a hrtimers flavor. So µs timeouts would be off the table?) Or I could use the interruptible version, and let the user kill the operation if necessary. Use a completion. Thanks, tglx
[Semaphore API] down_interruptible_timeout
Hello, The semaphore API provides several flavors of the down primitive: down, down_interruptible, down_killable, down_trylock, down_timeout As far as I can tell, they all call __down_common (except down_trylock, which returns 1 where the others would sleep). I was looking for a version 1) with a timeout 2) that could be interrupted e.g. down_interruptible_timeout, but it doesn't exist. It seems __down_common(sem, TASK_INTERRUPTIBLE, timeout); would work as expected, no? Do you know why it is not offered? (Maybe there is a better way to achieve the same thing?) [POST SCRIPTUM EDIT] I found this 2007 discussion: http://thread.gmane.org/gmane.linux.kernel/498034 At the time, Andrew said Nobody else has needed to invent new locking infrastructure to do such things and I'd prefer not to do so now. I suppose this is still true :-) [/EDIT] My use-case is pretty simple: A) process-context kernel thread fills a FIFO and calls down(fifo_empty); B) ISR handles the FIFO-empty interrupt with up(fifo_empty); However, in case something goes wrong and the interrupt never fires, I don't want the process to be stuck in an uninterruptible sleep. Perhaps I can set a tiny timeout (e.g. 10 µs) and not worry about the interruptible part for such a small duration? (Hmm, __down_common calls schedule_timeout, which is jiffies-based. I don't think there is a hrtimers flavor. So µs timeouts would be off the table?) Or I could use the interruptible version, and let the user kill the operation if necessary. I'd like to hear your comments and suggestions. Regards. -- To unsubscribe from this list: send the line unsubscribe linux-kernel in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
