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. > > 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/
