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* [RFC 0/12] introduce down_write_killable for rw_semaphore
@ 2016-02-02 20:19 ` Michal Hocko
  0 siblings, 0 replies; 64+ messages in thread
From: Michal Hocko @ 2016-02-02 20:19 UTC (permalink / raw)
  To: LKML
  Cc: Peter Zijlstra, Ingo Molnar, Thomas Gleixner, H. Peter Anvin,
	David S. Miller, Tony Luck, Andrew Morton, Chris Zankel,
	Max Filippov, x86, linux-alpha, linux-ia64, linux-s390, linux-sh,
	sparclinux, linux-xtensa, linux-arch

Hi,
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 [1] 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
  Documentation/memory-barriers.txt.
- 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 4-9 are implementing arch specific __down_write_killable. One
  patch per architecture. I haven't even tried to compile test anything but
  sparch which uses CONFIG_RWSEM_GENERIC_SPINLOCK in allnoconfig.
  Those shold be mostly trivial.
- One exception is x86 which replaces the current implementation of
  __down_write with the generic one to make easier to read and get rid
  of one level of indirection to the slow path. More on that in patch 10.
  I do not have any problems to drop patch 10 and rework 11 to the current
  inline asm but I think the easier code would be better.
- 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 not finished yet but I guess it is not
really necessary for the RFC. The API is used in the same way as
mutex_lock_killable.

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
by SIGKILL.

Patches should apply cleanly on both Linus and next tree.

Any feedback is highly appreciated.
---
[1] http://lkml.kernel.org/r/1452094975-551-1-git-send-email-mhocko@kernel.org


^ permalink raw reply	[flat|nested] 64+ messages in thread

end of thread, other threads:[~2016-06-10 17:59 UTC | newest]

Thread overview: 64+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2016-02-02 20:19 [RFC 0/12] introduce down_write_killable for rw_semaphore Michal Hocko
2016-02-02 20:19 ` Michal Hocko
2016-02-02 20:19 ` [RFC 01/12] locking, rwsem: get rid of __down_write_nested Michal Hocko
2016-02-02 20:19   ` Michal Hocko
2016-02-02 20:19 ` [RFC 02/12] locking, rwsem: drop explicit memory barriers Michal Hocko
2016-02-02 20:19   ` Michal Hocko
2016-02-02 20:19 ` [RFC 03/12] locking, rwsem: introduce basis for down_write_killable Michal Hocko
2016-02-02 20:19   ` Michal Hocko
2016-02-02 20:19 ` [RFC 04/12] alpha, rwsem: provide __down_write_killable Michal Hocko
2016-02-02 20:19   ` Michal Hocko
2016-02-02 20:19 ` [RFC 05/12] ia64, " Michal Hocko
2016-02-02 20:19   ` Michal Hocko
2016-02-02 20:19 ` [RFC 06/12] s390, " Michal Hocko
2016-02-02 20:19   ` Michal Hocko
2016-02-02 20:19 ` [RFC 07/12] sh, " Michal Hocko
2016-02-02 20:19   ` Michal Hocko
2016-02-03 11:19   ` Sergei Shtylyov
2016-02-03 11:19     ` Sergei Shtylyov
2016-02-03 12:11     ` Michal Hocko
2016-02-03 12:11       ` Michal Hocko
2016-02-02 20:19 ` [RFC 08/12] sparc, " Michal Hocko
2016-02-02 20:19   ` Michal Hocko
2016-02-02 20:19 ` [RFC 09/12] xtensa, " Michal Hocko
2016-02-02 20:19   ` Michal Hocko
2016-02-02 20:19 ` [RFC 10/12] x86, rwsem: simplify __down_write Michal Hocko
2016-02-02 20:19   ` Michal Hocko
2016-02-03  8:10   ` Ingo Molnar
2016-02-03  8:10     ` Ingo Molnar
2016-02-03 12:10     ` Michal Hocko
2016-02-03 12:10       ` Michal Hocko
2016-06-03 16:13     ` Peter Zijlstra
2016-06-03 16:13       ` Peter Zijlstra
2016-06-03 22:34       ` Peter Zijlstra
2016-06-03 22:34         ` Peter Zijlstra
2016-06-09 14:40       ` David Howells
2016-06-09 14:40         ` David Howells
2016-06-09 17:36         ` Peter Zijlstra
2016-06-09 17:36           ` Peter Zijlstra
2016-06-10 16:39           ` Paul E. McKenney
2016-06-10 16:39             ` Paul E. McKenney
2016-02-02 20:19 ` [RFC 11/12] x86, rwsem: provide __down_write_killable Michal Hocko
2016-02-02 20:19   ` Michal Hocko
2016-02-17 16:41   ` [RFC 11/12 v1] " Michal Hocko
2016-02-17 16:41     ` Michal Hocko
2016-02-17 16:41     ` Michal Hocko
2016-02-17 16:41     ` Michal Hocko
2016-02-02 20:19 ` [RFC 12/12] locking, rwsem: provide down_write_killable Michal Hocko
2016-02-02 20:19   ` Michal Hocko
2016-02-19 12:15 ` [RFC 0/12] introduce down_write_killable for rw_semaphore Michal Hocko
2016-02-19 12:15   ` Michal Hocko
2016-03-09 12:18 ` Ingo Molnar
2016-03-09 12:18   ` Ingo Molnar
2016-03-09 12:56   ` Michal Hocko
2016-03-09 12:56     ` Michal Hocko
2016-03-09 13:17     ` Ingo Molnar
2016-03-09 13:17       ` Ingo Molnar
2016-03-09 13:28       ` Michal Hocko
2016-03-09 13:28         ` Michal Hocko
2016-03-09 13:43         ` Ingo Molnar
2016-03-09 13:43           ` Ingo Molnar
2016-03-09 14:41           ` Michal Hocko
2016-03-09 14:41             ` Michal Hocko
2016-03-10 10:24             ` Ingo Molnar
2016-03-10 10:24               ` Ingo Molnar

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