On Tue, Jan 29, 2002 at 12:54:41AM -0800, Ulrich Drepper wrote:
> "H . J . Lu" <hjl@lucon.org> writes:
>
> > Here is a modified ex2.c which only uses one conditional variable. It
> > works fine on x86. But it leads to dead lock on mips where both
> > producer and consumer are suspended. Is this testcase correct?
>
>
> Therefore your revised code is not acceptable although it probably
> will almost always work.
>
It seems that the usage of ll/sc in glibc is wrong when they are used
to implement the compare/set operations. With this patch, the testcase
works now on mips when glibc is compiled with -mips2. Could someone
please double check my changes? If they are really correct, I will
verify other ll/sc usages in glibc.
Thanks.
H.J.
-----.
2002-01-29 H.J. Lu <hjl@gnu.org>
* sysdeps/mips/pt-machine.h (testandset): Return 1 when failed
to set.
(__compare_and_swap): Return 0 when failed to compare or swap.
--- linuxthreads/sysdeps/mips/pt-machine.h.llsc Mon Jan 28 18:02:45 2002
+++ linuxthreads/sysdeps/mips/pt-machine.h Tue Jan 29 16:59:46 2002
@@ -42,16 +42,12 @@ testandset (int *spinlock)
__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"
+ "bnez %0,1f\n\t"
+ "li %1,1\n\t"
"sc %1,%2\n\t"
- "beqz %1,1b\n"
- "2:\n\t"
+ "sltu %0,%1,1\n"
+ "1:\n\t"
"/* End spinlock test & set */"
: "=&r" (ret), "=&r" (temp), "=m" (*spinlock)
: "m" (*spinlock)
@@ -84,22 +80,18 @@ 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"
+ "move %0,$0\n\t"
+ "ll %1,%5\n\t"
+ "bne %1,%3,1f\n\t"
+ "move %0,%4\n\t"
+ "sc %0,%2\n"
"1:\n\t"
- "ll %0,%4\n\t"
- ".set push\n"
- ".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"
- "2:\n\t"
"/* End compare & swap */"
- : "=&r" (ret), "=m" (*p)
+ : "=&r" (ret), "=&r" (temp), "=m" (*p)
: "r" (oldval), "r" (newval), "m" (*p)
: "memory");
