On Tue, Mar 18, 2014 at 10:05 PM, Peter Zijlstra <pet...@infradead.org> wrote: > On Tue, Mar 18, 2014 at 09:51:04PM +0800, Peng Tao wrote: >> > Firstly I think the _head postfix for LIFO is a bad name, >> Do you have any preference on the name? add_wait_queue_exclusive_lifo()? > > I think we can avoid the entire function if we add > WQ_FLAG_LIFO and make prepare_to_wait_event() DTRT. > > Then we only need to teach ___wait() about this; and I suppose we could > make .exclusive=-1 be the LIFO flag. > > Unless you cannot use ___wait() and really need to open-code the > wait_event() stuff. > Lustre's private l_wait_event() stuff takes care to (un)mask LUSTRE_FATAL_SIGS and always wait in TASK_INTERRUPTIBLE state.
It looks to me that we can at least wrap l_wait_event() on top of wait_event_interruptible/wait_event_timeout_interruptible. Andreas, any opinions? Was l_wait_event added just for cross platform support or is there some deeper reason that I missed? Thanks, Tao >> > If you don't mix exclusive and !exclusive tasks on the same waitqueue >> > this isn't a problem, but I'm sure people will eventually do this and >> > get a nasty surprise. >> > >> Yes, Lustre takes care not to mix exclusive and !exclusive tasks in this >> case. > > Right; I saw you had a comment to that effect after I wrote this email. > >> > I'm not sure what the best way around this would be; but I can see two >> > options: >> > >> > - add enough debugging bits to detect this fail case. >> > - extend wait_queue_head_t to keep a pointer to the first !exclusive > > s/!// > >> > element and insert exclusive LIFO tasks there -- thereby keeping >> > !exclusive tasks at the front. >> > >> Thank you for the suggestions. Personally I am in favor of the second >> one but I'll wait others to comment first. > > Oleg, Ingo, any preferences? -- 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/
