Messages in this thread |  | | Subject | Re: NPTL mutex and the scheduling priority | From | Sébastien Dugué <> | Date | Tue, 13 Jun 2006 14:04:32 +0200 |
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On Tue, 2006-06-13 at 04:48 -0400, Jakub Jelinek wrote: > On Mon, Jun 12, 2006 at 05:24:28PM +0200, S?bastien Dugu? wrote: > > The patch you refer to is at > > http://marc.theaimsgroup.com/?l=linux-kernel&m=114725326712391&w=2 > > > > But maybe a better solution for condvars would be to implement > > something like a futex_requeue_pi() to handle the broadcast and > > only use PI futexes all along in glibc. > > FUTEX_REQUEUE certainly should be able to requeue from normal futex > to a PI futex or vice versa, I don't think it is desirable to create > a separate futex cmds for that.
Indeed, that would be preferable but might get tricky.
> Now not sure what do you mean by "use PI futexes all along in glibc", > certainly you don't mean using them for normal mutexes, right? > FUTEX_LOCK_PI has effects the normal futexes shouldn't have. > The condvars can be also used with PP mutexes and using PI for the cv > internal lock unconditionally wouldn't be the right thing either.
I effectively meant using a PI futex for the cv __data.__futex but now I realize it's a Really Bad Idea.
To summarize (correct me if I'm wrong), we need a way in the broadcast case to promote the cv __data.__futex type to the type of the external mutex (PI, PP, normal) in the requeue path. Therefore we need the ability to requeue waiters on a regular futex onto a PI futex.
Ingo, Thomas, is this feasible?
Sébastien.
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