From: Hugh Dickins <hughd@google.com>
To: Andrey Konovalov <andreyknvl@google.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
Michal Hocko <mhocko@suse.cz>,
Johannes Weiner <hannes@cmpxchg.org>,
Vladimir Davydov <vdavydov@parallels.com>,
Hugh Dickins <hughd@google.com>,
Miklos Szeredi <mszeredi@suse.cz>, Jason Low <jason.low2@hp.com>,
Cesar Eduardo Barros <cesarb@cesarb.net>,
linux-mm@kvack.org, linux-kernel@vger.kernel.org,
Dmitry Vyukov <dvyukov@google.com>,
Kostya Serebryany <kcc@google.com>,
Alexander Potapenko <glider@google.com>
Subject: Re: Potential data race in SyS_swapon
Date: Mon, 17 Aug 2015 16:22:21 -0700 (PDT) [thread overview]
Message-ID: <alpine.LSU.2.11.1508171610190.2618@eggly.anvils> (raw)
In-Reply-To: <CAAeHK+w7bQtAUAWFrcqE5Gf8t8nZoHim6iXg1axXdC_bVmrNDw@mail.gmail.com>
On Fri, 7 Aug 2015, Andrey Konovalov wrote:
>
> We are working on a dynamic data race detector for the Linux kernel
> called KernelThreadSanitizer (ktsan)
> (https://github.com/google/ktsan/wiki).
>
> While running ktsan on the upstream revision 21bdb584af8c with trinity
> we got a few reports from SyS_swapon, here is one of them:
>
> ==================================================================
> ThreadSanitizer: data-race in SyS_swapon
>
> Read of size 8 by thread T307 (K7621):
> [< inlined >] SyS_swapon+0x3c0/0x1850 SYSC_swapon mm/swapfile.c:2395
> [<ffffffff812242c0>] SyS_swapon+0x3c0/0x1850 mm/swapfile.c:2345
> [<ffffffff81e97c8a>] ia32_do_call+0x1b/0x25
>
> Looks like the swap_lock should be taken when iterating through the
> swap_info array on lines 2392 - 2401.
Thanks for the report. Actually, lines 2392 to 2401 just look redundant
to me: it looks as if claim_swapfile() should do all that's needed,
though in fact it doesn't quite. I'll send akpm a patch and Cc you,
no need to retest since the offending lines just won't be there.
Hugh
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next prev parent reply other threads:[~2015-08-17 23:23 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-08-07 16:14 Andrey Konovalov
2015-08-07 23:32 ` Cesar Eduardo Barros
2015-08-17 23:22 ` Hugh Dickins [this message]
2015-08-18 0:34 ` [PATCH] mm: fix potential " Hugh Dickins
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