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Date: Mon, 9 Nov 2009 10:01:43 +0100 From: Ingo Molnar <mingo@...e.hu> To: Jiri Slaby <jirislaby@...il.com> Cc: Neil Horman <nhorman@...driver.com>, Stephen Rothwell <sfr@...b.auug.org.au>, linux-kernel@...r.kernel.org, akpm@...ux-foundation.org, marcin.slusarz@...il.com, tglx@...utronix.de, mingo@...hat.com, hpa@...or.com, Linus Torvalds <torvalds@...ux-foundation.org> Subject: Re: [PATCH 0/3] extend get/setrlimit to support setting rlimits external to a process (v7) * Jiri Slaby <jirislaby@...il.com> wrote: > On 11/06/2009 10:26 AM, Ingo Molnar wrote: > > Also, the locking there looks messy: > > > > + /* optimization: 'current' doesn't need locking, e.g. setrlimit */ > > + if (tsk != current) { > > + /* protect tsk->signal and tsk->sighand from disappearing */ > > + read_lock(&tasklist_lock); > > + if (!tsk->sighand) { > > + retval = -ESRCH; > > + goto out; > > + } > > } > > > > Neil's splitup into a helper function looks _far_ cleaner. > > Oops, I don't understand here. Looking at > http://patchwork.kernel.org/patch/54863/ > and > http://decibel.fi.muni.cz/cgi-bin/gitweb.cgi?p=linux.git;a=commitdiff;h=ba9ba971a9241250646091935d77d2f31b7c15af > > They are almost identical. That 'if' above is added by: > http://decibel.fi.muni.cz/cgi-bin/gitweb.cgi?p=linux.git;a=commitdiff;h=bab65b1e6c0fd797a1ecdb32911faa82947effd0 > > The latter commit is to avoid performance penalty introduced for > setrlimit syscall by the added lock (as it's unneeded for 'current'). > If you find that crappy, there is no problem to drop it, indeed. Looks a bit ugly but i agree that it's a real speedup as before this change we never had to take the tasklist lock for current task rlimit setting. (which was the only method possible.) So i guess renaming setrlimit to do_setrlimit and adding the syscall from Neil's patch should bring the two series into sync, right? Ingo -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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