locking/pvqspinlock: Replace xchg() by the more descriptive set_mb()
The xchg() function was used in pv_wait_node() to set a certain value and provide a memory barrier which is what the set_mb() function is for. This patch replaces the xchg() call by set_mb(). Suggested-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Waiman Long <Waiman.Long@hp.com> Cc: Douglas Hatch <doug.hatch@hp.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Scott J Norton <scott.norton@hp.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: linux-kernel@vger.kernel.org Signed-off-by: Ingo Molnar <mingo@kernel.org>
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@ -175,7 +175,7 @@ static void pv_wait_node(struct mcs_spinlock *node)
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*
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* Matches the xchg() from pv_kick_node().
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*/
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(void)xchg(&pn->state, vcpu_halted);
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set_mb(pn->state, vcpu_halted);
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if (!READ_ONCE(node->locked))
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pv_wait(&pn->state, vcpu_halted);
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