diff options
| -rw-r--r-- | linuxthreads/ChangeLog | 20 | ||||
| -rw-r--r-- | linuxthreads/internals.h | 7 | ||||
| -rw-r--r-- | linuxthreads/spinlock.c | 17 | ||||
| -rw-r--r-- | linuxthreads/sysdeps/alpha/pt-machine.h | 12 | ||||
| -rw-r--r-- | linuxthreads/sysdeps/powerpc/pt-machine.h | 9 | ||||
| -rw-r--r-- | linuxthreads/sysdeps/sparc/sparc32/pt-machine.h | 5 | ||||
| -rw-r--r-- | linuxthreads/sysdeps/sparc/sparc64/pt-machine.h | 8 |
7 files changed, 61 insertions, 17 deletions
diff --git a/linuxthreads/ChangeLog b/linuxthreads/ChangeLog index 86e02aac61..9802ccf8ed 100644 --- a/linuxthreads/ChangeLog +++ b/linuxthreads/ChangeLog @@ -1,3 +1,23 @@ +2000-04-11 Ulrich Drepper <drepper@redhat.com> + + * internals.h: Define MEMORY_BARRIER as empty if not defined already. + * spinlock.c (__pthread_lock): Add memory barriers. + (__pthread_unlock): Likewise. + * sysdeps/alpha/pt-machine.h (MEMORY_BARRIER): Define using mb + instruction. + (RELEASE): Not needed anymore. + (__compare_and_swap): Mark asm as modifying memory. + * sysdeps/powerpc/pt-machine.h (sync): Remove. Replace with definition + of MEMORY_BARRIER. + (__compare_and_swap): Use MEMORY_BARRIER instead of sync. + * sysdeps/sparc/sparc32/pt-machine.h (RELEASE): Not needed anymore. + (MEMORY_BARRIER): Define using stbar. + * sysdeps/sparc/sparc64/pt-machine.h (MEMORY_BARRIER): Define using + stbar. + (__compare_and_swap): Use MEMORY_BARRIER to ensure ordering. + Patch by Xavier Leroy <Xavier.Leroy@inria.fr> based on comments by + Mike Burrows <m3b@pa.dec.com>. + 2000-04-09 Ulrich Drepper <drepper@redhat.com> * signals.c (sigaction): Fix return value for the case SIG is one diff --git a/linuxthreads/internals.h b/linuxthreads/internals.h index 8cb9b6837c..3984512e4d 100644 --- a/linuxthreads/internals.h +++ b/linuxthreads/internals.h @@ -357,6 +357,13 @@ static inline pthread_descr thread_self (void) #endif } +/* If MEMORY_BARRIER isn't defined in pt-machine.h, assume the architecture + doesn't need a memory barrier instruction (e.g. Intel x86) */ + +#ifndef MEMORY_BARRIER +#define MEMORY_BARRIER() +#endif + /* Max number of times we must spin on a spinlock calling sched_yield(). After MAX_SPIN_COUNT iterations, we put the calling thread to sleep. */ diff --git a/linuxthreads/spinlock.c b/linuxthreads/spinlock.c index b1a99d9753..e1c40c05d0 100644 --- a/linuxthreads/spinlock.c +++ b/linuxthreads/spinlock.c @@ -54,6 +54,9 @@ void internal_function __pthread_lock(struct _pthread_fastlock * lock, if (self != NULL) { ASSERT(self->p_nextlock == NULL); THREAD_SETMEM(self, p_nextlock, (pthread_descr) oldstatus); + /* Make sure the store in p_nextlock completes before performing + the compare-and-swap */ + MEMORY_BARRIER(); } } while(! compare_and_swap(&lock->__status, oldstatus, newstatus, &lock->__spinlock)); @@ -108,8 +111,17 @@ again: maxprio = thr->p_priority; } ptr = &(thr->p_nextlock); + /* Prevent reordering of the load of lock->__status above and the + load of *ptr below, as well as reordering of *ptr between + several iterations of the while loop. Some processors (e.g. + multiprocessor Alphas) could perform such reordering even though + the loads are dependent. */ + MEMORY_BARRIER(); thr = *ptr; } + /* Prevent reordering of the load of lock->__status above and + thr->p_nextlock below */ + MEMORY_BARRIER(); /* Remove max prio thread from waiting list. */ if (maxptr == (pthread_descr *) &lock->__status) { /* If max prio thread is at head, remove it with compare-and-swap @@ -124,6 +136,9 @@ again: thr = *maxptr; *maxptr = thr->p_nextlock; } + /* Prevent reordering of store to *maxptr above and store to thr->p_nextlock + below */ + MEMORY_BARRIER(); /* Wake up the selected waiting thread */ thr->p_nextlock = NULL; restart(thr); @@ -149,6 +164,8 @@ int __pthread_compare_and_swap(long * ptr, long oldval, long newval, } else { res = 0; } + /* Prevent reordering of store to *ptr above and store to *spinlock below */ + MEMORY_BARRIER(); *spinlock = 0; return res; } diff --git a/linuxthreads/sysdeps/alpha/pt-machine.h b/linuxthreads/sysdeps/alpha/pt-machine.h index e59c6906c8..25ba634528 100644 --- a/linuxthreads/sysdeps/alpha/pt-machine.h +++ b/linuxthreads/sysdeps/alpha/pt-machine.h @@ -32,6 +32,10 @@ register char *stack_pointer __asm__("$30"); +/* Memory barrier; default is to do nothing */ +#define MEMORY_BARRIER() __asm__ __volatile__("mb" : : : "memory") + + /* Spinlock implementation; required. */ PT_EI long int testandset (int *spinlock) @@ -55,11 +59,6 @@ testandset (int *spinlock) return ret; } -/* Spinlock release; default is just set to zero. */ -#define RELEASE(spinlock) \ - __asm__ __volatile__("mb" : : : "memory"); \ - *spinlock = 0 - /* Begin allocating thread stacks at this address. Default is to allocate them just below the initial program stack. */ @@ -102,7 +101,8 @@ __compare_and_swap (long int *p, long int oldval, long int newval) "2:\tmb\n" "/* End compare & swap */" : "=&r"(ret), "=m"(*p) - : "r"(oldval), "r"(newval), "m"(*p)); + : "r"(oldval), "r"(newval), "m"(*p) + : "memory"); return ret; } diff --git a/linuxthreads/sysdeps/powerpc/pt-machine.h b/linuxthreads/sysdeps/powerpc/pt-machine.h index 578369a7fe..c7d0670d82 100644 --- a/linuxthreads/sysdeps/powerpc/pt-machine.h +++ b/linuxthreads/sysdeps/powerpc/pt-machine.h @@ -27,12 +27,7 @@ /* For multiprocessor systems, we want to ensure all memory accesses are completed before we reset a lock. */ -#if 0 -/* on non multiprocessor systems, you can just: */ -#define sync() /* nothing */ -#else -#define sync() __asm__ __volatile__ ("sync") -#endif +#define MEMORY_BARRIER() __asm__ __volatile__ ("sync" : : : "memory") /* Get some notion of the current stack. Need not be exactly the top of the stack, just something somewhere in the current frame. */ @@ -64,6 +59,6 @@ __compare_and_swap (long int *p, long int oldval, long int newval) : "=&r"(ret) : "r"(p), "r"(newval), "r"(oldval) : "cr0", "memory"); - sync(); + MEMORY_BARRIER(); return ret == 0; } diff --git a/linuxthreads/sysdeps/sparc/sparc32/pt-machine.h b/linuxthreads/sysdeps/sparc/sparc32/pt-machine.h index 69af8579aa..ddf4932af9 100644 --- a/linuxthreads/sysdeps/sparc/sparc32/pt-machine.h +++ b/linuxthreads/sysdeps/sparc/sparc32/pt-machine.h @@ -37,9 +37,8 @@ testandset (int *spinlock) } -/* Spinlock release; default is just set to zero. */ -#define RELEASE(spinlock) \ - __asm__ __volatile__("stbar; stb %1,%0" : "=m"(*(spinlock)) : "r"(0)); +/* Memory barrier; default is to do nothing */ +#define MEMORY_BARRIER() __asm__ __volatile__("stbar" : : : "memory") /* Get some notion of the current stack. Need not be exactly the top diff --git a/linuxthreads/sysdeps/sparc/sparc64/pt-machine.h b/linuxthreads/sysdeps/sparc/sparc64/pt-machine.h index 5560003fc8..02167bd601 100644 --- a/linuxthreads/sysdeps/sparc/sparc64/pt-machine.h +++ b/linuxthreads/sysdeps/sparc/sparc64/pt-machine.h @@ -37,6 +37,12 @@ testandset (int *spinlock) } +/* Memory barrier; default is to do nothing */ +/* FIXME: is stbar OK, or should we use the more general membar instruction? + If so, which mode to pass to membar? */ +#define MEMORY_BARRIER() __asm__ __volatile__("stbar" : : : "memory") + + /* Get some notion of the current stack. Need not be exactly the top of the stack, just something somewhere in the current frame. */ #define CURRENT_STACK_FRAME stack_pointer @@ -66,7 +72,7 @@ __compare_and_swap (long int *p, long int oldval, long int newval) __asm__ __volatile__ ("casx [%4], %2, %0" : "=r"(readval), "=m"(*p) : "r"(oldval), "m"(*p), "r"(p), "0"(newval)); - + MEMORY_BARRIER(); return readval == oldval; } |