forge/linux-uconsole
1
0
Fork 0
Code Issues 1 Pull requests Projects Releases Packages Wiki Activity Actions
linux-uconsole/include
History
Will Deacon d0179ca85e mutex: Place lock in contended state after fastpath_lock failure 
commit 0bce9c46bf upstream.

ARM recently moved to asm-generic/mutex-xchg.h for its mutex
implementation after the previous implementation was found to be missing
some crucial memory barriers. However, this has revealed some problems
running hackbench on SMP platforms due to the way in which the
MUTEX_SPIN_ON_OWNER code operates.

The symptoms are that a bunch of hackbench tasks are left waiting on an
unlocked mutex and therefore never get woken up to claim it. This boils
down to the following sequence of events:

        Task A        Task B        Task C        Lock value
0                                                     1
1       lock()                                        0
2                     lock()                          0
3                     spin(A)                         0
4       unlock()                                      1
5                                   lock()            0
6                     cmpxchg(1,0)                    0
7                     contended()                    -1
8       lock()                                        0
9       spin(C)                                       0
10                                  unlock()          1
11      cmpxchg(1,0)                                  0
12      unlock()                                      1

At this point, the lock is unlocked, but Task B is in an uninterruptible
sleep with nobody to wake it up.

This patch fixes the problem by ensuring we put the lock into the
contended state if we fail to acquire it on the fastpath, ensuring that
any blocked waiters are woken up when the mutex is released.

Signed-off-by: Will Deacon <will.deacon@arm.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Chris Mason <chris.mason@fusionio.com>
Cc: Ingo Molnar <mingo@elte.hu>
Reviewed-by: Nicolas Pitre <nico@linaro.org>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/n/tip-6e9lrw2avczr0617fzl5vqb8@git.kernel.org
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2012-10-02 09:47:39 -07:00
..
acpi ACPI: Store SRAT table revision 2012-01-25 17:24:57 -08:00
asm-generic mutex: Place lock in contended state after fastpath_lock failure 2012-10-02 09:47:39 -07:00
crypto
drm drm/radeon/kms: add new BTC PCI ids 2012-06-10 00:33:04 +09:00
keys
linux NFS: Fix the initialisation of the readdir 'cookieverf' array 2012-10-02 09:47:38 -07:00
math-emu
media [media] tuner-core/v4l2-subdev: document that the type field has to be filled in 2011-07-07 15:04:23 -03:00
mtd
net tcp: Apply device TSO segment limit earlier 2012-10-02 09:47:04 -07:00
pcmcia
rdma Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/roland/infiniband 2011-05-26 12:13:57 -07:00
rxrpc
scsi [SCSI] libsas: Add option for SATA soft reset 2011-05-26 22:49:33 -05:00
sound ALSA: sb16 - Fix build errors on MIPS and others with 13bit ioctl size 2011-06-30 15:33:57 +02:00
target target: Set additional sense length field in sense data 2012-01-25 17:25:00 -08:00
trace tracing: Don't call page_to_pfn() if page is NULL 2012-10-02 09:47:27 -07:00
video OMAPDSS: HDMI: PHY burnout fix 2012-03-12 10:32:59 -07:00
xen xen/xenbus: Reject replies with payload > XENSTORE_PAYLOAD_MAX. 2012-01-25 17:24:41 -08:00
Kbuild