From mboxrd@z Thu Jan 1 00:00:00 1970 From: Davidlohr Bueso Subject: Re: Next round: revised futex(2) man page for review Date: Tue, 28 Jul 2015 19:09:19 -0700 Message-ID: <1438135759.2249.94.camel@stgolabs.net> References: <55B61EF3.7080302@gmail.com> <20150728204508.GG19282@twins.programming.kicks-ass.net> Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20150728204508.GG19282-ndre7Fmf5hadTX5a5knrm8zTDFooKrT+cvkQGrU6aU0@public.gmane.org> Sender: linux-man-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Peter Zijlstra Cc: Thomas Gleixner , "Michael Kerrisk (man-pages)" , Darren Hart , Torvald Riegel , Carlos O'Donell , Ingo Molnar , Jakub Jelinek , linux-man , lkml , Arnd Bergmann , Steven Rostedt , Linux API , Roland McGrath , Anton Blanchard , Eric Dumazet , bill o gallmeister , Jan Kiszka , Daniel Wagner , Rich Felker , Andy Lutomirski , bert hubert , Rusty Russell , Heinrich Schuchardt List-Id: linux-api@vger.kernel.org On Tue, 2015-07-28 at 22:45 +0200, Peter Zijlstra wrote: > Also, this code seems to use plist, which means it won't do the right > thing for SCHED_DEADLINE either. Ick, I don't look forward to seeing nice futex plists converted into rbtrees. As opposed to, eg. rtmutexes, there are a few caveats: - Dealing with the top_waiter in rtmutexes is always easy, but in futexes we need to deal with keys, so caching the leftmost won't work as nicely. - This will bloat things like futex_wake, where O(logN) is not suited for FIFO iteration. And iterating linked lists is, in essence, all that we really do when calling futex(2). I have to wonder about the extra overhead added by these points. I do understand the dl concern, nonetheless. -- To unsubscribe from this list: send the line "unsubscribe linux-man" in the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org More majordomo info at http://vger.kernel.org/majordomo-info.html