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Commit 491f6f8e authored by Heiko Carstens's avatar Heiko Carstens
Browse files

lockref: use arch_mutex_cpu_relax() in CMPXCHG_LOOP() 



Make use of arch_mutex_cpu_relax() so architectures can override the
default cpu_relax() semantics.
This is especially useful for s390, where cpu_relax() means that we
yield() the current (virtual) cpu and therefore is very expensive,
and would contradict the whole purpose of the lockless cmpxchg loop.

Signed-off-by: default avatarHeiko Carstens <heiko.carstens@de.ibm.com>
parent 083986e8

lib/lockref.c

+9 −1
Original line number Original line Diff line number Diff line
@@ -11,6 +11,14 @@ 
# define cmpxchg64_relaxed cmpxchg64

# define cmpxchg64_relaxed cmpxchg64

#endif

#endif





/*

 * Allow architectures to override the default cpu_relax() within CMPXCHG_LOOP.

 * This is useful for architectures with an expensive cpu_relax().

 */

#ifndef arch_mutex_cpu_relax

# define arch_mutex_cpu_relax() cpu_relax()

#endif



/*

/*

 * Note that the "cmpxchg()" reloads the "old" value for the

 * Note that the "cmpxchg()" reloads the "old" value for the

 * failure case.

 * failure case.
@@ -28,7 +36,7 @@ 
		if (likely(old.lock_count == prev.lock_count)) {		\

		if (likely(old.lock_count == prev.lock_count)) {		\

			SUCCESS;						\

			SUCCESS;						\

		}								\

		}								\

		cpu_relax();							\

		arch_mutex_cpu_relax();						\

	}									\

	}									\

} while (0)

} while (0)