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authorLinus Torvalds <torvalds@macmini.osdl.org>2006-07-08 15:24:18 -0700
committerLinus Torvalds <torvalds@macmini.osdl.org>2006-07-08 15:24:18 -0700
commitb862f3b099f3ea672c7438c0b282ce8201d39dfc (patch)
tree62f8cc2dc2b1c9abb6364b16f3b218a04d121f3e /include/asm-i386/rwsem.h
parente2a3d40258fe20d205f8ed592e1e2c0d5529c2e1 (diff)
i386: improve and correct inline asm memory constraints
Use "+m" rather than a combination of "=m" and "m" for improved clarity and consistency. This also fixes some inlines that incorrectly didn't tell the compiler that they read the old value at all, potentially causing the compiler to generate bogus code. It appear that all of those potential bugs were hidden by the use of extra "volatile" specifiers on the data structures in question, though. Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Diffstat (limited to 'include/asm-i386/rwsem.h')
-rw-r--r--include/asm-i386/rwsem.h35
1 files changed, 17 insertions, 18 deletions
diff --git a/include/asm-i386/rwsem.h b/include/asm-i386/rwsem.h
index 2f07601562e..43113f5608e 100644
--- a/include/asm-i386/rwsem.h
+++ b/include/asm-i386/rwsem.h
@@ -111,8 +111,8 @@ LOCK_PREFIX " incl (%%eax)\n\t" /* adds 0x00000001, returns the old value
" jmp 1b\n"
LOCK_SECTION_END
"# ending down_read\n\t"
- : "=m"(sem->count)
- : "a"(sem), "m"(sem->count)
+ : "+m" (sem->count)
+ : "a" (sem)
: "memory", "cc");
}
@@ -133,8 +133,8 @@ LOCK_PREFIX " cmpxchgl %2,%0\n\t"
" jnz 1b\n\t"
"2:\n\t"
"# ending __down_read_trylock\n\t"
- : "+m"(sem->count), "=&a"(result), "=&r"(tmp)
- : "i"(RWSEM_ACTIVE_READ_BIAS)
+ : "+m" (sem->count), "=&a" (result), "=&r" (tmp)
+ : "i" (RWSEM_ACTIVE_READ_BIAS)
: "memory", "cc");
return result>=0 ? 1 : 0;
}
@@ -161,8 +161,8 @@ LOCK_PREFIX " xadd %%edx,(%%eax)\n\t" /* subtract 0x0000ffff, returns the
" jmp 1b\n"
LOCK_SECTION_END
"# ending down_write"
- : "=m"(sem->count), "=d"(tmp)
- : "a"(sem), "1"(tmp), "m"(sem->count)
+ : "+m" (sem->count), "=d" (tmp)
+ : "a" (sem), "1" (tmp)
: "memory", "cc");
}
@@ -205,8 +205,8 @@ LOCK_PREFIX " xadd %%edx,(%%eax)\n\t" /* subtracts 1, returns the old valu
" jmp 1b\n"
LOCK_SECTION_END
"# ending __up_read\n"
- : "=m"(sem->count), "=d"(tmp)
- : "a"(sem), "1"(tmp), "m"(sem->count)
+ : "+m" (sem->count), "=d" (tmp)
+ : "a" (sem), "1" (tmp)
: "memory", "cc");
}
@@ -231,8 +231,8 @@ LOCK_PREFIX " xaddl %%edx,(%%eax)\n\t" /* tries to transition 0xffff0001 ->
" jmp 1b\n"
LOCK_SECTION_END
"# ending __up_write\n"
- : "=m"(sem->count)
- : "a"(sem), "i"(-RWSEM_ACTIVE_WRITE_BIAS), "m"(sem->count)
+ : "+m" (sem->count)
+ : "a" (sem), "i" (-RWSEM_ACTIVE_WRITE_BIAS)
: "memory", "cc", "edx");
}
@@ -256,8 +256,8 @@ LOCK_PREFIX " addl %2,(%%eax)\n\t" /* transitions 0xZZZZ0001 -> 0xYYYY0001
" jmp 1b\n"
LOCK_SECTION_END
"# ending __downgrade_write\n"
- : "=m"(sem->count)
- : "a"(sem), "i"(-RWSEM_WAITING_BIAS), "m"(sem->count)
+ : "+m" (sem->count)
+ : "a" (sem), "i" (-RWSEM_WAITING_BIAS)
: "memory", "cc");
}
@@ -268,8 +268,8 @@ static inline void rwsem_atomic_add(int delta, struct rw_semaphore *sem)
{
__asm__ __volatile__(
LOCK_PREFIX "addl %1,%0"
- : "=m"(sem->count)
- : "ir"(delta), "m"(sem->count));
+ : "+m" (sem->count)
+ : "ir" (delta));
}
/*
@@ -280,10 +280,9 @@ static inline int rwsem_atomic_update(int delta, struct rw_semaphore *sem)
int tmp = delta;
__asm__ __volatile__(
-LOCK_PREFIX "xadd %0,(%2)"
- : "+r"(tmp), "=m"(sem->count)
- : "r"(sem), "m"(sem->count)
- : "memory");
+LOCK_PREFIX "xadd %0,%1"
+ : "+r" (tmp), "+m" (sem->count)
+ : : "memory");
return tmp+delta;
}