Commit 0dceeaf5 authored by Pan Xinhui's avatar Pan Xinhui Committed by Ingo Molnar
Browse files

locking/qspinlock: Use __this_cpu_dec() instead of full-blown this_cpu_dec()



queued_spin_lock_slowpath() should not worry about another
queued_spin_lock_slowpath() running in interrupt context and
changing node->count by accident, because node->count keeps
the same value every time we enter/leave queued_spin_lock_slowpath().

On some architectures this_cpu_dec() will save/restore irq flags,
which has high overhead. Use the much cheaper __this_cpu_dec() instead.
Signed-off-by: default avatarPan Xinhui <xinhui.pan@linux.vnet.ibm.com>
Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Waiman.Long@hpe.com
Link: http://lkml.kernel.org/r/1465886247-3773-1-git-send-email-xinhui.pan@linux.vnet.ibm.com


[ Rewrote changelog. ]
Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent ebff09a6
......@@ -619,7 +619,7 @@ void queued_spin_lock_slowpath(struct qspinlock *lock, u32 val)
/*
* release the node
*/
this_cpu_dec(mcs_nodes[0].count);
__this_cpu_dec(mcs_nodes[0].count);
}
EXPORT_SYMBOL(queued_spin_lock_slowpath);
......
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