Commit 77ba93a7 authored Dec 08, 2008 by Paul Mundt

sh: Fix up the SH-4A mutex fastpath semantics.

This fixes up the __mutex_fastpath_xxx() routines to match the semantics
noted in the comment. Previously these were looping rather than doing a
single-pass, which is counter-intuitive, as the slow path takes care of
the looping for us in the event of contention.

Signed-off-by: Paul Mundt <lethal@linux-sh.org>

parent c6f17cb2

arch/sh/include/asm/mutex-llsc.h

+21 −16

Original line number	Diff line number	Diff line
		@@ -21,16 +21,18 @@
		static inline void
		__mutex_fastpath_lock(atomic_t count, void (fail_fn)(atomic_t *))
		{
		int __res;
		int __ex_flag, __res;

		__asm__ __volatile__ (
		"movli.l @%1, %0 \n"
		"dt %0 \n"
		"movco.l %0, @%1 \n"
		: "=&z" (__res)
		"movli.l @%2, %0 \n"
		"add #-1, %0 \n"
		"movco.l %0, @%2 \n"
		"movt %1 \n"
		: "=&z" (__res), "=&r" (__ex_flag)
		: "r" (&(count)->counter)
		: "t");

		__res \|= !__ex_flag;
		if (unlikely(__res != 0))
		fail_fn(count);
		}
		@@ -38,16 +40,18 @@ __mutex_fastpath_lock(atomic_t count, void (fail_fn)(atomic_t *))
		static inline int
		__mutex_fastpath_lock_retval(atomic_t count, int (fail_fn)(atomic_t *))
		{
		int __res;
		int __ex_flag, __res;

		__asm__ __volatile__ (
		"movli.l @%1, %0 \n"
		"dt %0 \n"
		"movco.l %0, @%1 \n"
		: "=&z" (__res)
		"movli.l @%2, %0 \n"
		"add #-1, %0 \n"
		"movco.l %0, @%2 \n"
		"movt %1 \n"
		: "=&z" (__res), "=&r" (__ex_flag)
		: "r" (&(count)->counter)
		: "t");

		__res \|= !__ex_flag;
		if (unlikely(__res != 0))
		__res = fail_fn(count);

		@@ -57,18 +61,19 @@ __mutex_fastpath_lock_retval(atomic_t count, int (fail_fn)(atomic_t *))
		static inline void
		__mutex_fastpath_unlock(atomic_t count, void (fail_fn)(atomic_t *))
		{
		int __res;
		int __ex_flag, __res;

		__asm__ __volatile__ (
		"1: movli.l @%1, %0 \n\t"
		"movli.l @%2, %0 \n\t"
		"add #1, %0 \n\t"
		"movco.l %0, @%1 \n\t"
		"bf 1b\n\t"
		: "=&z" (__res)
		"movco.l %0, @%2 \n\t"
		"movt %1 \n\t"
		: "=&z" (__res), "=&r" (__ex_flag)
		: "r" (&(count)->counter)
		: "t");

		if (unlikely(__res <= 0))
		__res \|= !__ex_flag;
		if (unlikely(__res != 0))
		fail_fn(count);
		}