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D41936.diff
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diff --git a/lib/libc/stdlib/quick_exit.c b/lib/libc/stdlib/quick_exit.c
--- a/lib/libc/stdlib/quick_exit.c
+++ b/lib/libc/stdlib/quick_exit.c
@@ -2,6 +2,7 @@
* SPDX-License-Identifier: BSD-2-Clause
*
* Copyright (c) 2011 David Chisnall
+ * Copyright (c) 2023 Klara, Inc.
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
@@ -27,44 +28,35 @@
*/
#include <sys/types.h>
-#include <machine/atomic.h>
+
+#include <stdatomic.h>
#include <stdlib.h>
-#include <pthread.h>
/**
- * Linked list of quick exit handlers. This is simpler than the atexit()
- * version, because it is not required to support C++ destructors or
- * DSO-specific cleanups.
+ * Linked list of quick exit handlers. These will be invoked in reverse
+ * order of insertion when quick_exit() is called. This is simpler than
+ * the atexit() version, because it is not required to support C++
+ * destructors or DSO-specific cleanups.
*/
struct quick_exit_handler {
struct quick_exit_handler *next;
void (*cleanup)(void);
};
-/**
- * Lock protecting the handlers list.
- */
-static pthread_mutex_t atexit_mutex = PTHREAD_MUTEX_INITIALIZER;
-/**
- * Stack of cleanup handlers. These will be invoked in reverse order when
- */
-static struct quick_exit_handler *handlers;
+static _Atomic(struct quick_exit_handler *) handlers;
int
at_quick_exit(void (*func)(void))
{
struct quick_exit_handler *h;
-
- h = malloc(sizeof(*h));
- if (NULL == h)
- return (1);
+ if ((h = calloc(1, sizeof(*h))) == NULL) {
+ return (-1);
+ }
h->cleanup = func;
- pthread_mutex_lock(&atexit_mutex);
- h->next = handlers;
- __compiler_membar();
- handlers = h;
- pthread_mutex_unlock(&atexit_mutex);
+ while (!atomic_compare_exchange_strong(&handlers, &h->next, h)) {
+ /* nothing */ ;
+ }
return (0);
}
@@ -77,8 +69,8 @@
* XXX: The C++ spec requires us to call std::terminate if there is an
* exception here.
*/
- for (h = handlers; NULL != h; h = h->next) {
- __compiler_membar();
+ for (h = atomic_load_explicit(&handlers, memory_order_acquire);
+ h != NULL; h = h->next) {
h->cleanup();
}
_Exit(status);
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D41936: libc: Rewrite quick_exit() and at_quick_exit() using C11 atomics.
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