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From: Michal Hocko <>
To: LKML <>
Cc: Peter Zijlstra <>,
	Ingo Molnar <>,
	Thomas Gleixner <>,
	"H. Peter Anvin" <>,
	"David S. Miller" <>,
	Tony Luck <>,
	Andrew Morton <>,
	Chris Zankel <>,
	Max Filippov <>,,,,,,,,
Subject: [PATCH 0/11] introduce down_write_killable for rw_semaphore
Date: Mon, 29 Feb 2016 13:58:14 +0100
Message-ID: <> (raw)

I have posted this series [1] and there didn't seem to be any
fundamental objections except for x86 maintainers who preferred the asm
__down_write implementation which I have reworked for this series. Apart
from that I have refreshed on top of the current linux-next and fixed
one unused variable warning which happened to trigger a compilation
failure on ppc.

The following patchset implements a killable variant of write lock for
rw_semaphore. My usecase is to turn as many mmap_sem write users to use
a killable variant which will be helpful for the oom_reaper [2] to
asynchronously tear down the oom victim address space which requires
mmap_sem for read. This will reduce a likelihood of OOM livelocks caused
by oom victim being stuck on a lock or other resource which prevents it
to reach its exit path and release the memory. I haven't implemented
the killable variant of the read lock because I do not have any usecase
for this API.

The patchset is organized as follows.
- Patch 1 is a trivial cleanup
- Patch 2, I belive, shouldn't introduce any functional changes as per
- Patch 3 is the preparatory work and necessary infrastructure for
  down_write_killable. It implements generic __down_write_killable
  and prepares the write lock slow path to bail out earlier when told so
- Patch 4-1- are implementing arch specific __down_write_killable. One
  patch per architecture.
- finally patch 11 implements down_write_killable and ties everything
  together. I am not really an expert on lockdep so I hope I got it right.

Many of arch specific patches are basically same and I can squash them
into one patch if this is preferred but I thought that one patch per
arch is preferable.

My patch to change mmap_sem write users to killable form is not part of
the series because it is a larger change and I would like to prevent
from spamming people too much. I will post the series shortly.

I have tested on x86 with OOM situations with high mmap_sem contention
(basically many parallel page faults racing with many parallel mmap/munmap
tight loops) so the waiters for the write locks are routinely interrupted

Patches should apply cleanly on both Linus and next tree.


Any feedback is highly appreciated.

             reply index

Thread overview: 27+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-02-29 12:58 Michal Hocko [this message]
2016-02-29 12:58 ` [PATCH 01/11] locking, rwsem: get rid of __down_write_nested Michal Hocko
2016-02-29 12:58 ` [PATCH 02/11] locking, rwsem: drop explicit memory barriers Michal Hocko
2016-02-29 12:58 ` [PATCH 03/11] locking, rwsem: introduce basis for down_write_killable Michal Hocko
2016-03-30 13:25   ` Peter Zijlstra
2016-03-31  8:33     ` Michal Hocko
2016-03-31  8:44       ` Peter Zijlstra
2016-03-31  8:55   ` [PATCH] " Michal Hocko
2016-02-29 12:58 ` [PATCH 04/11] alpha, rwsem: provide __down_write_killable Michal Hocko
2016-02-29 12:58 ` [PATCH 05/11] ia64, " Michal Hocko
2016-02-29 12:58 ` [PATCH 06/11] s390, " Michal Hocko
2016-02-29 12:58 ` [PATCH 07/11] sh, " Michal Hocko
2016-02-29 12:58 ` [PATCH 08/11] sparc, " Michal Hocko
2016-02-29 12:58 ` [PATCH 09/11] xtensa, " Michal Hocko
2016-02-29 12:58 ` [PATCH 10/11] x86, " Michal Hocko
2016-02-29 12:58 ` [PATCH 11/11] locking, rwsem: provide down_write_killable Michal Hocko
2016-03-30 13:32 ` [PATCH 0/11] introduce down_write_killable for rw_semaphore Peter Zijlstra
2016-03-31  8:59   ` Michal Hocko
2016-03-31  9:20     ` Ingo Molnar
2016-03-31 10:58       ` Michal Hocko
2016-03-31 17:03       ` Andrew Morton
2016-04-01  6:33         ` Ingo Molnar
2016-04-01  9:21           ` Michal Hocko
2016-04-01  9:50             ` Ingo Molnar
2016-04-01 10:52               ` Michal Hocko
2016-04-01  7:26         ` Michal Hocko
2016-04-01  9:11           ` Andrew Morton

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