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From: Andrea Arcangeli <aarcange@redhat.com>
To: Dave Hansen <dave@linux.vnet.ibm.com>
Cc: Miklos Szeredi <miklos@szeredi.hu>,
	linux-fsdevel <linux-fsdevel@vger.kernel.org>,
	linux-mm <linux-mm@kvack.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	Lin Feng Shen <shenlinf@cn.ibm.com>,
	Yuri L Volobuev <volobuev@us.ibm.com>,
	Mel Gorman <mel@linux.vnet.ibm.com>,
	dingc@cn.ibm.com, lnxninja <lnxninja@us.ibm.com>
Subject: Re: Deadlocks with transparent huge pages and userspace fs daemons
Date: Tue, 14 Dec 2010 18:46:26 +0100	[thread overview]
Message-ID: <20101214174626.GN5638@random.random> (raw)
In-Reply-To: <1288817005.4235.11393.camel@nimitz>

Hello Dave and everyone,

On Wed, Nov 03, 2010 at 01:43:25PM -0700, Dave Hansen wrote:
> Hey Miklos,
> 
> When testing with a transparent huge page kernel:
> 
> 	http://git.kernel.org/gitweb.cgi?p=linux/kernel/git/andrea/aa.git;a=summary
> 
> some IBM testers ran into some deadlocks.  It appears that the
> khugepaged process is trying to migrate one of a filesystem daemon's
> pages while khugepaged holds the daemon's mmap_sem for write.

The allocation under mmap_sem write mode in khugepaged bug should be
fixed in current aa.git based on 37-rc5:

http://git.kernel.org/?p=linux/kernel/git/andrea/aa.git;a=shortlog
http://git.kernel.org/?p=linux/kernel/git/andrea/aa.git;a=commit;h=83e4d55d0014b3eeb982005d73f55ffcf2813504

Let me know how it goes, it's not very well tested yet (which is why I
didn't make a new submit yet).

I stick to my idea this is bug in userland and may trigger if your
daemon does mmap/munmap and the vma allocation under mmap_sem waits
for the I/O, but I don't want to show it with THP enabled, and this is
more scalable so it's definitely good idea and no downside whatsoever.

Thanks for the report,
Andrea

  parent reply	other threads:[~2010-12-14 17:46 UTC|newest]

Thread overview: 8+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2010-11-03 20:43 Deadlocks with transparent huge pages and userspace fs daemons Dave Hansen
2010-11-03 21:46 ` Miklos Szeredi
2010-11-04 16:41 ` Andrea Arcangeli
2010-11-04 19:53   ` Miklos Szeredi
2010-12-14 17:46 ` Andrea Arcangeli [this message]
2010-12-14 21:03   ` Miklos Szeredi
2010-12-15  5:24     ` Andrea Arcangeli
2010-12-15 14:54       ` Miklos Szeredi

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