Date: Thu, 22 May 2014 20:34:21 +0200 From: Hans Petter Selasky <hps@selasky.org> To: Chagin Dmitry <dchagin@freebsd.org> Cc: freebsd-multimedia@FreeBSD.org, FreeBSD Current <freebsd-current@freebsd.org> Subject: Re: Patch for Linux Futexes Message-ID: <537E432D.9060701@selasky.org> In-Reply-To: <20140522182343.GA2825@dchagin.static.corbina.net> References: <537DDA2E.6030609@selasky.org> <20140522182343.GA2825@dchagin.static.corbina.net>
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On 05/22/14 20:23, Chagin Dmitry wrote: > On Thu, May 22, 2014 at 01:06:22PM +0200, Hans Petter Selasky wrote: >> Hi, >> >> When using the Linux Skype client under FreeBSD I sometimes see that the >> Audio disappears in the one direction. When I check "ps auxw" I see >> skype is stuck on a so-called Futex. I looked into the Linux futex code >> and see that wakeup_one() is used instead of wakeup(). Maybe others can >> test too and verify if replacing wakeup_one() by wakeup() makes any >> difference in for Linux applications using Futexes. >> > > generally speaking the patch is not correct as futex_wake() should > wakeup n waiters which is specified by user space. and i think that > futex_wake() is correct. > so we must take a close look at futex_requeue() and FUTEX_WAKE_OP. > > Hi, I still see the issue with Skype, even when running with my small patch :-( I'll try to profile the threads in Skype while it is running like expected and observe any differences when it is not working, when I have some more time, using kgdb. I guess td->td_slptick can be used to figure out if a thread has been left behind, because Skype creates many threads ... Thank you for your time! --HPS
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