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Index: head/sys/mips/include/atomic.h
===================================================================
--- head/sys/mips/include/atomic.h
+++ head/sys/mips/include/atomic.h
@@ -397,18 +397,25 @@
{
int ret;
+ /*
+ * The following sequence (similar to that in atomic_fcmpset_64) will
+ * attempt to update the value of *p with newval if the comparison
+ * succeeds. Note that they'll exit regardless of whether the store
+ * actually succeeded, leaving *cmpval untouched. This is in line with
+ * the documentation of atomic_fcmpset_<type>() in atomic(9) for ll/sc
+ * architectures.
+ */
__asm __volatile (
- "1:\n\t"
"ll %0, %1\n\t" /* load old value */
- "bne %0, %4, 2f\n\t" /* compare */
+ "bne %0, %4, 1f\n\t" /* compare */
"move %0, %3\n\t" /* value to store */
"sc %0, %1\n\t" /* attempt to store */
- "beqz %0, 1b\n\t" /* if it failed, spin */
- "j 3f\n\t"
- "2:\n\t"
+ "j 2f\n\t" /* exit regardless of success */
+ "nop\n\t" /* avoid delay slot accident */
+ "1:\n\t"
"sw %0, %2\n\t" /* save old value */
"li %0, 0\n\t"
- "3:\n"
+ "2:\n"
: "=&r" (ret), "+m" (*p), "=m" (*cmpval)
: "r" (newval), "r" (*cmpval)
: "memory");
@@ -508,17 +515,16 @@
int ret;
__asm __volatile (
- "1:\n\t"
"lld %0, %1\n\t" /* load old value */
- "bne %0, %4, 2f\n\t" /* compare */
+ "bne %0, %4, 1f\n\t" /* compare */
"move %0, %3\n\t" /* value to store */
"scd %0, %1\n\t" /* attempt to store */
- "beqz %0, 1b\n\t" /* if it failed, spin */
- "j 3f\n\t"
- "2:\n\t"
+ "j 2f\n\t" /* exit regardless of success */
+ "nop\n\t" /* avoid delay slot accident */
+ "1:\n\t"
"sd %0, %2\n\t" /* save old value */
"li %0, 0\n\t"
- "3:\n"
+ "2:\n"
: "=&r" (ret), "+m" (*p), "=m" (*cmpval)
: "r" (newval), "r" (*cmpval)
: "memory");

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