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Revert "[compiler-rt][builtins] Switch libatomic locks to pthread_mutex_t (#94374)"

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This reverts commit b62b7a42bbee4a3bbf9094808f460fdc9c119bd7 and
a5729b71d844c1444f7d348dc2d4ea5b98de5ec5.

This commit broke compilation for systems that lack pthreads.
This commit is contained in:
Martin Storsjö 2024-06-05 22:49:58 +03:00
parent 3beb232fb4
commit a4b32c2576
1 changed files with 13 additions and 18 deletions
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31
compiler-rt/lib/builtins/atomic.c
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@ -51,14 +51,6 @@
#endif
static const long SPINLOCK_MASK = SPINLOCK_COUNT - 1;
#ifndef CACHE_LINE_SIZE
#define CACHE_LINE_SIZE 64
#endif
#ifdef __clang__
#pragma clang diagnostic ignored "-Wgnu-designator"
#endif
////////////////////////////////////////////////////////////////////////////////
// Platform-specific lock implementation. Falls back to spinlocks if none is
// defined. Each platform should define the Lock type, and corresponding
@ -102,18 +94,21 @@ static Lock locks[SPINLOCK_COUNT]; // initialized to OS_SPINLOCK_INIT which is 0
#else
_Static_assert(__atomic_always_lock_free(sizeof(uintptr_t), 0),
"Implementation assumes lock-free pointer-size cmpxchg");
#include <pthread.h>
#include <stdalign.h>
typedef struct {
alignas(CACHE_LINE_SIZE) pthread_mutex_t m;
} Lock;
typedef _Atomic(uintptr_t) Lock;
/// Unlock a lock. This is a release operation.
__inline static void unlock(Lock *l) { pthread_mutex_unlock(&l->m); }
/// Locks a lock.
__inline static void lock(Lock *l) { pthread_mutex_lock(&l->m); }
__inline static void unlock(Lock *l) {
__c11_atomic_store(l, 0, __ATOMIC_RELEASE);
}
/// Locks a lock. In the current implementation, this is potentially
/// unbounded in the contended case.
__inline static void lock(Lock *l) {
uintptr_t old = 0;
while (!__c11_atomic_compare_exchange_weak(l, &old, 1, __ATOMIC_ACQUIRE,
__ATOMIC_RELAXED))
old = 0;
}
/// locks for atomic operations
static Lock locks[SPINLOCK_COUNT] = {
[0 ... SPINLOCK_COUNT - 1] = {PTHREAD_MUTEX_INITIALIZER}};
static Lock locks[SPINLOCK_COUNT];
#endif
/// Returns a lock to use for a given pointer.