linux-kernel - [PATCH 0/4] ipc/sem.c: Bug fixes, regression fixes, v3

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Date:	Sun, 26 May 2013 11:08:51 +0200
From:	Manfred Spraul <manfred@...orfullife.com>
To:	Rik van Riel <riel@...hat.com>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Davidlohr Bueso <davidlohr.bueso@...com>, hhuang@...hat.com,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Manfred Spraul <manfred@...orfullife.com>
Subject: [PATCH 0/4] ipc/sem.c: Bug fixes, regression fixes, v3

I've split my patch into 4 parts:
- 1: Fix-missing-wakeups-in-do_smart_update
- 2: seperate-wait-for-zero-and-alter-tasks
- 3: Always-use-only-one-queue-for-alter-operations
- 4: Rename-try_atomic_semop-to-perform_atomic

Linus:
- Patch 1 should be merged immediately: It fixes bugs,
  the current code misses wakeups.

- Patch 2 and 3 restore the behavior of linux <=3.0.9.
  I would propose that they are merged, too: I can't rule out that
  changing the priority of the wakeups breaks user space apps.

- Patch 4 is trivial, no code changes at all.
  If 2+3 are merged, then 4 should be merged, too.

I have tested patch 1 seperately and 1+2+3+4:
With patch 1 applied, there are no more missed wakeups.

With all 4 applied, linux-3.0.10-rc1 behaves as linux <=3.0.9.

With regards to the scalability, I do not expect any degradation:
Operations on seperate semaphores in an array remain parallelized.

Apps that use lots of wait-for-zero semop are probably even faster,
because the wait-for-zero ops are now only scanned if a semval is 0.

--
	Manfred
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