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From: Michal Hocko <mhocko@kernel.org>
To: Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>
Cc: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>,
	Andrea Arcangeli <aarcange@redhat.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	Vlastimil Babka <vbabka@suse.cz>,
	"Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
	Stephen Rothwell <sfr@canb.auug.org.au>,
	linux-mm@kvack.org, linux-next@vger.kernel.org,
	linux-kernel@vger.kernel.org
Subject: Re: [linux-next: Tree for Jun 1] __khugepaged_exit rwsem_down_write_failed lockup
Date: Mon, 6 Jun 2016 10:39:46 +0200	[thread overview]
Message-ID: <20160606083946.GG11895@dhcp22.suse.cz> (raw)
In-Reply-To: <20160604075114.GA21108@swordfish>

On Sat 04-06-16 16:51:14, Sergey Senozhatsky wrote:
> Hello,
> 
> On (06/03/16 15:49), Michal Hocko wrote:
> > __khugepaged_exit is called during the final __mmput and it employs a
> > complex synchronization dances to make sure it doesn't race with the
> > khugepaged which might be scanning this mm at the same time. This is
> > all caused by the fact that khugepaged doesn't pin mm_users. Things
> > would simplify considerably if we simply check the mm at
> > khugepaged_scan_mm_slot and if mm_users was already 0 then we know it
> > is dead and we can unhash the mm_slot and move on to another one. This
> > will also guarantee that __khugepaged_exit cannot race with khugepaged
> > and so we can free up the slot if it is still hashed.
> > 
> > Signed-off-by: Michal Hocko <mhocko@suse.com>
> 
> with this patch and
> http://ozlabs.org/~akpm/mmotm/broken-out/mm-thp-make-swapin-readahead-under-down_read-of-mmap_sem-fix-2.patch
> 
> I saw no problems during my tests (well, may be didn't test hard
> enough).

Thanks for the testing!
-- 
Michal Hocko
SUSE Labs

WARNING: multiple messages have this Message-ID (diff)
From: Michal Hocko <mhocko@kernel.org>
To: Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>
Cc: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>,
	Andrea Arcangeli <aarcange@redhat.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	Vlastimil Babka <vbabka@suse.cz>,
	"Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
	Stephen Rothwell <sfr@canb.auug.org.au>,
	linux-mm@kvack.org, linux-next@vger.kernel.org,
	linux-kernel@vger.kernel.org
Subject: Re: [linux-next: Tree for Jun 1] __khugepaged_exit rwsem_down_write_failed lockup
Date: Mon, 6 Jun 2016 10:39:46 +0200	[thread overview]
Message-ID: <20160606083946.GG11895@dhcp22.suse.cz> (raw)
In-Reply-To: <20160604075114.GA21108@swordfish>

On Sat 04-06-16 16:51:14, Sergey Senozhatsky wrote:
> Hello,
> 
> On (06/03/16 15:49), Michal Hocko wrote:
> > __khugepaged_exit is called during the final __mmput and it employs a
> > complex synchronization dances to make sure it doesn't race with the
> > khugepaged which might be scanning this mm at the same time. This is
> > all caused by the fact that khugepaged doesn't pin mm_users. Things
> > would simplify considerably if we simply check the mm at
> > khugepaged_scan_mm_slot and if mm_users was already 0 then we know it
> > is dead and we can unhash the mm_slot and move on to another one. This
> > will also guarantee that __khugepaged_exit cannot race with khugepaged
> > and so we can free up the slot if it is still hashed.
> > 
> > Signed-off-by: Michal Hocko <mhocko@suse.com>
> 
> with this patch and
> http://ozlabs.org/~akpm/mmotm/broken-out/mm-thp-make-swapin-readahead-under-down_read-of-mmap_sem-fix-2.patch
> 
> I saw no problems during my tests (well, may be didn't test hard
> enough).

Thanks for the testing!
-- 
Michal Hocko
SUSE Labs

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  reply	other threads:[~2016-06-06  8:39 UTC|newest]

Thread overview: 56+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-06-01  3:11 linux-next: Tree for Jun 1 Stephen Rothwell
2016-06-02  1:48 ` [linux-next: Tree for Jun 1] __khugepaged_exit rwsem_down_write_failed lockup Sergey Senozhatsky
2016-06-02  1:48   ` Sergey Senozhatsky
2016-06-02  9:21   ` Michal Hocko
2016-06-02  9:21     ` Michal Hocko
2016-06-02 12:08     ` Sergey Senozhatsky
2016-06-02 12:08       ` Sergey Senozhatsky
2016-06-02 12:21       ` Michal Hocko
2016-06-02 12:21         ` Michal Hocko
2016-06-03 13:51         ` Andrea Arcangeli
2016-06-03 13:51           ` Andrea Arcangeli
2016-06-03 14:46           ` Michal Hocko
2016-06-03 14:46             ` Michal Hocko
2016-06-03 15:10             ` Andrea Arcangeli
2016-06-03 15:10               ` Andrea Arcangeli
2016-06-07  7:34               ` Michal Hocko
2016-06-07  7:34                 ` Michal Hocko
2016-06-08  8:19               ` Vlastimil Babka
2016-06-08  8:19                 ` Vlastimil Babka
2016-06-03  7:15     ` Sergey Senozhatsky
2016-06-03  7:15       ` Sergey Senozhatsky
2016-06-03  7:25       ` Michal Hocko
2016-06-03  7:25         ` Michal Hocko
2016-06-03  8:43         ` Sergey Senozhatsky
2016-06-03  8:43           ` Sergey Senozhatsky
2016-06-03  9:55           ` Michal Hocko
2016-06-03  9:55             ` Michal Hocko
2016-06-03 10:05             ` Michal Hocko
2016-06-03 10:05               ` Michal Hocko
2016-06-03 13:38               ` Sergey Senozhatsky
2016-06-03 13:38                 ` Sergey Senozhatsky
2016-06-03 13:45                 ` Michal Hocko
2016-06-03 13:45                   ` Michal Hocko
2016-06-03 13:49                   ` Michal Hocko
2016-06-03 13:49                     ` Michal Hocko
2016-06-03 13:49                     ` Michal Hocko
2016-06-04  7:51                     ` Sergey Senozhatsky
2016-06-04  7:51                       ` Sergey Senozhatsky
2016-06-06  8:39                       ` Michal Hocko [this message]
2016-06-06  8:39                         ` Michal Hocko
2016-06-02 13:24   ` Vlastimil Babka
2016-06-02 13:24     ` Vlastimil Babka
2016-06-02 18:58     ` Ebru Akagunduz
2016-06-02 18:58       ` Ebru Akagunduz
2016-06-03  1:00       ` Sergey Senozhatsky
2016-06-03  1:00         ` Sergey Senozhatsky
2016-06-03  1:29         ` Sergey Senozhatsky
2016-06-03  1:29           ` Sergey Senozhatsky
2016-06-03  4:14           ` Sergey Senozhatsky
2016-06-03  4:14             ` Sergey Senozhatsky
2016-06-03 12:28     ` [PATCH] mm, thp: fix locking inconsistency in collapse_huge_page Ebru Akagunduz
2016-06-03 12:28       ` Ebru Akagunduz
2016-06-06 13:05       ` Vlastimil Babka
2016-06-06 13:05         ` Vlastimil Babka
2016-06-09  3:51         ` Sergey Senozhatsky
2016-06-09  3:51           ` Sergey Senozhatsky

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