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Date: Thu, 14 May 2015 19:38:49 +0200 From: Ingo Molnar <mingo@...nel.org> To: Milos Vyletel <milos@...hat.com> Cc: Jiri Olsa <jolsa@...hat.com>, Peter Zijlstra <a.p.zijlstra@...llo.nl>, Paul Mackerras <paulus@...ba.org>, Ingo Molnar <mingo@...hat.com>, Arnaldo Carvalho de Melo <acme@...nel.org>, Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>, Namhyung Kim <namhyung@...nel.org>, Jiri Olsa <jolsa@...nel.org>, He Kuang <hekuang@...wei.com>, Adrian Hunter <adrian.hunter@...el.com>, "open list:PERFORMANCE EVENT..." <linux-kernel@...r.kernel.org> Subject: Re: [PATCH 2/2] perf/tools: put new buildid locks to use * Milos Vyletel <milos@...hat.com> wrote: > On Thu, May 14, 2015 at 01:38:21PM +0200, Jiri Olsa wrote: > > > On Thu, May 14, 2015 at 12:40:59PM +0200, Ingo Molnar wrote: > > > > > > * Milos Vyletel <milos@...hat.com> wrote: > > > > > > > Use new read/write locks when accesing buildid directory on places where > > > > we may race if multiple instances are run simultaneously. > > > > > > Dunno, this will create locking interaction between multiple instances > > > of perf - hanging each other, etc. > > > > > > And it seems unnecessary: the buildid hierarchy is already spread out. > > > What kind of races might there be? > > > > there was just recently one fixed by commit: > > 0635b0f71424 perf tools: Fix race in build_id_cache__add_s() > > > > havent checked the final patch yet, but the idea is to > > protect us from similar bugs > > right. on top of race with EEXIST couple more are possible (EMLINK, > ENOSPC, EDQUOT, ENOMEM... the only way to prevent them all is to > lock this kind of operations and make sure we run one at a time. No, that's not the only way to avoid the race - see my previous mail. Thanks, 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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