On Fri, Feb 01, 2002 at 12:50:48PM +0100, Maciej W. Rozycki wrote:
> On Fri, 1 Feb 2002, Hiroyuki Machida wrote:
>
> > > It will fail if *p is not same as oldval.
> >
> > Please note that "sc" may fail even if nobody write the
> > variable. (See P.211 "8.4.2 Load-Linked/Sotre-Conditional" of "See
> > MIPS RUN" for more detail.)
> > So, after your patch applied, compare_and_swap() may fail, even if
> > *p is equal to oldval.
>
> That's exactly what I meant -- "sc" may fail to execute the store, while
> "cmpxchgl" may not.
>
Here is the updated patch.
H.J.
---
2002-01-31 H.J. Lu <hjl@gnu.org>
* sysdeps/mips/pspinlock.c (__pthread_spin_lock): Use a
different register in the delayed slot.
* sysdeps/mips/pt-machine.h (testandset): Call _test_and_set.
(__compare_and_swap): Return 0 only when failed to compare.
2002-01-31 H.J. Lu <hjl@gnu.org>
* sysdeps/mips/atomicity.h (compare_and_swap): Return 0 only
when failed to compare.
* sysdeps/unix/sysv/linux/mips/sys/tas.h (_test_and_set): Fill
the delay slot.
--- glibc-2.2.4/linuxthreads/sysdeps/mips/pspinlock.c.llsc Thu Jan 31 10:49:37 2002
+++ glibc-2.2.4/linuxthreads/sysdeps/mips/pspinlock.c Thu Jan 31 10:49:37 2002
@@ -29,20 +29,21 @@
int
__pthread_spin_lock (pthread_spinlock_t *lock)
{
- unsigned int tmp;
+ unsigned int tmp1, tmp2;
asm volatile
("\t\t\t# spin_lock\n\t"
- "1:\n\t"
- "ll %1,%2\n\t"
".set push\n\t"
- ".set noreorder\n\t"
+ ".set noreorder\n"
+ "1:\n\t"
+ "ll %1,%3\n\t"
"bnez %1,1b\n\t"
- " li %1,1\n\t"
- ".set pop\n\t"
- "sc %1,%0\n\t"
- "beqz %1,1b"
- : "=m" (*lock), "=&r" (tmp)
+ "li %2,1\n\t"
+ "sc %2,%0\n\t"
+ "beqz %2,1b\n\t"
+ "nop\n\t"
+ ".set pop"
+ : "=m" (*lock), "=&r" (tmp1), "=&r" (tmp2)
: "m" (*lock)
: "memory");
--- glibc-2.2.4/linuxthreads/sysdeps/mips/pt-machine.h.llsc Sat Dec 9 08:55:34 2000
+++ glibc-2.2.4/linuxthreads/sysdeps/mips/pt-machine.h Fri Feb 1 09:19:44 2002
@@ -33,41 +33,11 @@
/* Spinlock implementation; required. */
-#if (_MIPS_ISA >= _MIPS_ISA_MIPS2)
-
-PT_EI long int
-testandset (int *spinlock)
-{
- long int ret, temp;
-
- __asm__ __volatile__
- ("/* Inline spinlock test & set */\n\t"
- "1:\n\t"
- "ll %0,%3\n\t"
- ".set push\n\t"
- ".set noreorder\n\t"
- "bnez %0,2f\n\t"
- " li %1,1\n\t"
- ".set pop\n\t"
- "sc %1,%2\n\t"
- "beqz %1,1b\n"
- "2:\n\t"
- "/* End spinlock test & set */"
- : "=&r" (ret), "=&r" (temp), "=m" (*spinlock)
- : "m" (*spinlock)
- : "memory");
-
- return ret;
-}
-
-#else /* !(_MIPS_ISA >= _MIPS_ISA_MIPS2) */
-
PT_EI long int
testandset (int *spinlock)
{
return _test_and_set (spinlock, 1);
}
-#endif /* !(_MIPS_ISA >= _MIPS_ISA_MIPS2) */
/* Get some notion of the current stack. Need not be exactly the top
@@ -84,22 +54,24 @@ register char * stack_pointer __asm__ ("
PT_EI int
__compare_and_swap (long int *p, long int oldval, long int newval)
{
- long int ret;
+ long int ret, temp;
__asm__ __volatile__
- ("/* Inline compare & swap */\n\t"
+ ("/* Inline compare & swap */\n"
"1:\n\t"
- "ll %0,%4\n\t"
- ".set push\n"
+ "ll %1,%5\n\t"
+ ".set push\n\t"
".set noreorder\n\t"
- "bne %0,%2,2f\n\t"
- " move %0,%3\n\t"
- ".set pop\n\t"
- "sc %0,%1\n\t"
- "beqz %0,1b\n"
+ "bne %1,%3,2f\n\t"
+ "move %0,$0\n\t"
+ "move %0,%4\n\t"
+ "sc %0,%2\n\t"
+ "beqz %0,1b\n\t"
+ "nop\n\t"
+ ".set pop\n"
"2:\n\t"
"/* End compare & swap */"
- : "=&r" (ret), "=m" (*p)
+ : "=&r" (ret), "=&r" (temp), "=m" (*p)
: "r" (oldval), "r" (newval), "m" (*p)
: "memory");
--- glibc-2.2.4/sysdeps/mips/atomicity.h.llsc Mon Jul 9 11:58:19 2001
+++ glibc-2.2.4/sysdeps/mips/atomicity.h Fri Feb 1 09:21:41 2002
@@ -32,12 +32,16 @@ exchange_and_add (volatile uint32_t *mem
int result, tmp;
__asm__ __volatile__
- ("/* Inline exchange & add */\n\t"
+ ("/* Inline exchange & add */\n"
"1:\n\t"
"ll %0,%3\n\t"
"addu %1,%4,%0\n\t"
"sc %1,%2\n\t"
+ ".set push\n\t"
+ ".set noreorder\n\t"
"beqz %1,1b\n\t"
+ "nop\n\t"
+ ".set pop\n\t"
"/* End exchange & add */"
: "=&r"(result), "=&r"(tmp), "=m"(*mem)
: "m" (*mem), "r"(val)
@@ -53,12 +57,16 @@ atomic_add (volatile uint32_t *mem, int
int result;
__asm__ __volatile__
- ("/* Inline atomic add */\n\t"
+ ("/* Inline atomic add */\n"
"1:\n\t"
"ll %0,%2\n\t"
"addu %0,%3,%0\n\t"
"sc %0,%1\n\t"
+ ".set push\n\t"
+ ".set noreorder\n\t"
"beqz %0,1b\n\t"
+ "nop\n\t"
+ ".set pop\n\t"
"/* End atomic add */"
: "=&r"(result), "=m"(*mem)
: "m" (*mem), "r"(val)
@@ -69,22 +77,24 @@ static inline int
__attribute__ ((unused))
compare_and_swap (volatile long int *p, long int oldval, long int newval)
{
- long int ret;
+ long int ret, temp;
__asm__ __volatile__
- ("/* Inline compare & swap */\n\t"
+ ("/* Inline compare & swap */\n"
"1:\n\t"
- "ll %0,%4\n\t"
- ".set push\n"
+ "ll %1,%5\n\t"
+ ".set push\n\t"
".set noreorder\n\t"
- "bne %0,%2,2f\n\t"
- "move %0,%3\n\t"
- ".set pop\n\t"
- "sc %0,%1\n\t"
- "beqz %0,1b\n"
+ "bne %1,%3,2f\n\t"
+ "move %0,$0\n\t"
+ "move %0,%4\n\t"
+ "sc %0,%2\n\t"
+ "beqz %0,1b\n\t"
+ "nop\n\t"
+ ".set pop\n"
"2:\n\t"
"/* End compare & swap */"
- : "=&r" (ret), "=m" (*p)
+ : "=&r" (ret), "=&r" (temp), "=m" (*p)
: "r" (oldval), "r" (newval), "m" (*p)
: "memory");
--- glibc-2.2.4/sysdeps/unix/sysv/linux/mips/sys/tas.h.llsc Mon Jul 9 11:58:45 2001
+++ glibc-2.2.4/sysdeps/unix/sysv/linux/mips/sys/tas.h Thu Jan 31 10:49:37 2002
@@ -42,16 +42,17 @@ _test_and_set (int *p, int v) __THROW
int r, t;
__asm__ __volatile__
- ("1:\n\t"
+ (".set push\n\t"
+ ".set noreorder\n"
+ "1:\n\t"
"ll %0,%3\n\t"
- ".set push\n\t"
- ".set noreorder\n\t"
"beq %0,%4,2f\n\t"
- " move %1,%4\n\t"
- ".set pop\n\t"
+ "move %1,%4\n\t"
"sc %1,%2\n\t"
- "beqz %1,1b\n"
- "2:\n"
+ "beqz %1,1b\n\t"
+ "nop\n"
+ "2:\n\t"
+ ".set pop"
: "=&r" (r), "=&r" (t), "=m" (*p)
: "m" (*p), "r" (v)
: "memory");
