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authorJianyu Zhan <nasa4836@gmail.com>2016-03-07 09:32:24 +0800
committerThomas Gleixner <tglx@linutronix.de>2016-03-08 17:04:02 +0100
commit29b75eb2d56a714190a93d7be4525e617591077a (patch)
tree07f13028b74665bf757523864dc2478426974c54 /lib
parent9e4e7554e755aaad8df0e26268787438735b4b76 (diff)
downloadlinux-29b75eb2d56a714190a93d7be4525e617591077a.tar.bz2
futex: Replace barrier() in unqueue_me() with READ_ONCE()
Commit e91467ecd1ef ("bug in futex unqueue_me") introduced a barrier() in unqueue_me() to prevent the compiler from rereading the lock pointer which might change after a check for NULL. Replace the barrier() with a READ_ONCE() for the following reasons: 1) READ_ONCE() is a weaker form of barrier() that affects only the specific load operation, while barrier() is a general compiler level memory barrier. READ_ONCE() was not available at the time when the barrier was added. 2) Aside of that READ_ONCE() is descriptive and self explainatory while a barrier without comment is not clear to the casual reader. No functional change. [ tglx: Massaged changelog ] Signed-off-by: Jianyu Zhan <nasa4836@gmail.com> Acked-by: Christian Borntraeger <borntraeger@de.ibm.com> Acked-by: Darren Hart <dvhart@linux.intel.com> Cc: dave@stgolabs.net Cc: peterz@infradead.org Cc: linux@rasmusvillemoes.dk Cc: akpm@linux-foundation.org Cc: fengguang.wu@intel.com Cc: bigeasy@linutronix.de Link: http://lkml.kernel.org/r/1457314344-5685-1-git-send-email-nasa4836@gmail.com Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
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