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Subject[PATCH] __up_read and gcc-3.0
Hi Alan,
can you apply this patch to next 2.4.4-acX ? This fixes problem with
gcc3.0 (20010426) unable to compile this under some conditions. As
__up_write() uses same code ("i".... instead of tmp variable), I think
that you should apply this. It can cause slower code, as gcc cannot
move "movl -RWSEM_ACTIVE_READ_BIAS,%edx" away from "xadd" anymore,
but as "lock xadd" is slow anyway, it should not matter.

I looked at generated code in cases where it originally failed, and
generated code looks OK to me.
Thanks,
Petr Vandrovec
vandrove@vc.cvut.cz


diff -urdN linux/include/asm-i386/rwsem.h linux/include/asm-i386/rwsem.h
--- linux/include/asm-i386/rwsem.h Fri Apr 27 22:48:24 2001
+++ linux/include/asm-i386/rwsem.h Wed May 9 16:31:57 2001
@@ -148,9 +148,9 @@
*/
static inline void __up_read(struct rw_semaphore *sem)
{
- __s32 tmp = -RWSEM_ACTIVE_READ_BIAS;
__asm__ __volatile__(
"# beginning __up_read\n\t"
+ " movl %2,%%edx\n\t"
LOCK_PREFIX " xadd %%edx,(%%eax)\n\t" /* subtracts 1, returns the old value */
" js 2f\n\t" /* jump if the lock is being waited upon */
"1:\n\t"
@@ -164,9 +164,9 @@
" jmp 1b\n"
".previous\n"
"# ending __up_read\n"
- : "+m"(sem->count), "+d"(tmp)
- : "a"(sem)
- : "memory", "cc");
+ : "+m"(sem->count)
+ : "a"(sem), "i"(-RWSEM_ACTIVE_READ_BIAS)
+ : "memory", "cc", "edx");
}

/*
-
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