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Enable file locking in musl stdio (emscripten-core#15065)
This is second attempt at landing a version of emscripten-core@d5d5f69 The first time we tried it emscripten-core#13837 we ran into issues with test_pthread_exit_process deadlocking which I tracked down to an issue with `system/lib/libc/musl/src/thread/__wait.c` where it was blocking the main thread forever rather then looping and calling `emscripten_main_thread_process_queued_calls`. Includes a version of emscripten-core#14481 so that should land before this does. Fixes: emscripten-core#13194
1 parent 8b84169 commit fdd486f

11 files changed

Lines changed: 117 additions & 4 deletions

‎system/lib/libc/musl/src/thread/__wait.c‎

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@@ -1,10 +1,13 @@
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#ifdef __EMSCRIPTEN__
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#include <math.h>
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#include <emscripten/threading.h>
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#endif
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#include "pthread_impl.h"
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#ifdef __EMSCRIPTEN__
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int _pthread_isduecanceled(struct pthread *pthread_ptr);
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#endif
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void __wait(volatile int *addr, volatile int *waiters, int val, int priv)
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{
@@ -18,7 +21,7 @@ void __wait(volatile int *addr, volatile int *waiters, int val, int priv)
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#ifdef __EMSCRIPTEN__
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int is_main_thread = emscripten_is_main_runtime_thread();
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while (*addr==val) {
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if (pthread_self()->cancelasync == PTHREAD_CANCEL_ASYNCHRONOUS) {
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if (is_main_thread || pthread_self()->cancelasync == PTHREAD_CANCEL_ASYNCHRONOUS) {
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// Must wait in slices in case this thread is cancelled in between.
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int e;
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do {

‎system/lib/pthread/pthread_create.c‎

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@@ -7,6 +7,7 @@
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#define _GNU_SOURCE
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#include "pthread_impl.h"
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#include "stdio_impl.h"
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#include "assert.h"
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#include <pthread.h>
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#include <stdbool.h>
@@ -53,6 +54,15 @@ void __do_cleanup_pop(struct __ptcb *cb) {
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__pthread_self()->cancelbuf = cb->__next;
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}
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static FILE *volatile dummy_file = 0;
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weak_alias(dummy_file, __stdin_used);
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weak_alias(dummy_file, __stdout_used);
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weak_alias(dummy_file, __stderr_used);
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static void init_file_lock(FILE *f) {
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if (f && f->lock<0) f->lock = 0;
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}
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int __pthread_create(pthread_t *restrict res, const pthread_attr_t *restrict attrp, void *(*entry)(void *), void *restrict arg) {
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// Note on LSAN: lsan intercepts/wraps calls to pthread_create so any
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// allocation we we do here should be considered leaks.
@@ -61,6 +71,16 @@ int __pthread_create(pthread_t *restrict res, const pthread_attr_t *restrict att
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return EINVAL;
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}
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if (!libc.threaded) {
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for (FILE *f=*__ofl_lock(); f; f=f->next)
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init_file_lock(f);
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__ofl_unlock();
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init_file_lock(__stdin_used);
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init_file_lock(__stdout_used);
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init_file_lock(__stderr_used);
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libc.threaded = 1;
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}
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// Allocate thread block (pthread_t structure).
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struct pthread *new = malloc(sizeof(struct pthread));
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// zero-initialize thread structure.

‎tests/core/test_stdio_locking.c‎

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/*
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* Regression test for stdio locking. If file locking is not enabled the
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* threads will race to write the file output buffer and we will see lines
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* that are longer or shorter then 100 characters. When locking is
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* working/enabled each 100 charactor line will be printed seperately.
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*
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* See:
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* musl/src/stdio/__lockfile.c
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* musl/src/stdio/fwrite.c
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*/
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#include <assert.h>
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#include <pthread.h>
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#include <stdio.h>
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#include <string.h>
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#include <stdlib.h>
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pthread_t thread[2];
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char *char_repeat(int n, char c) {
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char *dest = malloc(n + 1);
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memset(dest, c, n);
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dest[n] = '\0';
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return dest;
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}
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void *thread_main(void *arg) {
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char *msg = char_repeat(100, 'a');
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for (int i = 0; i < 10; ++i)
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printf("%s\n", msg);
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free(msg);
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return 0;
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}
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int main() {
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printf("in main\n");
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void *thread_rtn;
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int rc;
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rc = pthread_create(&thread[0], NULL, thread_main, NULL);
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assert(rc == 0);
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rc = pthread_create(&thread[1], NULL, thread_main, NULL);
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assert(rc == 0);
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rc = pthread_join(thread[0], &thread_rtn);
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assert(rc == 0);
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assert(thread_rtn == 0);
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rc = pthread_join(thread[1], &thread_rtn);
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assert(rc == 0);
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assert(thread_rtn == 0);
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printf("main done\n");
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return 0;
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}

‎tests/core/test_stdio_locking.out‎

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in main
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aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
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aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
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aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
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aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
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aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
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aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
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aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
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aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
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aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
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aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
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aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
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aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
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aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
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aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
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aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
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aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
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aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
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aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
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aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
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aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
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main done

‎tests/other/metadce/minimal_main_Oz_USE_PTHREADS_PROXY_TO_PTHREAD.exports‎

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N
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O
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P
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v
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Q
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w
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x
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y

‎tests/other/metadce/minimal_main_Oz_USE_PTHREADS_PROXY_TO_PTHREAD.funcs‎

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$GetQueue
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$__emscripten_init_main_thread
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$__emscripten_stdout_seek
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$__errno_location
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$__pthread_mutex_lock
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$__pthread_mutex_trylock
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$__pthread_mutex_unlock
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$__pthread_self_internal
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$__pthread_setcancelstate
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$__stdio_write
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$__wasi_syscall_ret
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$__wasm_call_ctors
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$__wasm_init_memory
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$_do_call
@@ -34,9 +37,11 @@ $emscripten_sync_run_in_main_thread
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$emscripten_sync_run_in_main_thread
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$emscripten_tls_init
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$free_tls
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$init_file_lock
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$init_mparams
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$main
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$memset
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$pthread_mutexattr_destroy
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$sbrk
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$stackAlloc
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$stackRestore

‎tests/other/metadce/minimal_main_Oz_USE_PTHREADS_PROXY_TO_PTHREAD.imports‎

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a.s
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a.t
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a.u
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a.v

‎tests/other/metadce/minimal_main_Oz_USE_PTHREADS_PROXY_TO_PTHREAD.sent‎

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s
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t
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u
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v

‎tests/other/metadce/minimal_main_Oz_USE_PTHREADS_PROXY_TO_PTHREAD.size‎

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16977

‎tests/test_core.py‎

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@@ -8406,6 +8406,12 @@ def test_emscripten_futexes(self):
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self.set_setting('USE_PTHREADS')
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self.do_run_in_out_file_test('core/pthread/emscripten_futexes.c')
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8409+
@node_pthreads
8410+
def test_stdio_locking(self):
8411+
self.set_setting('PTHREAD_POOL_SIZE', '2')
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self.set_setting('EXIT_RUNTIME')
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self.do_run_in_out_file_test('core', 'test_stdio_locking.c')
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@needs_dylink
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@node_pthreads
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def test_pthread_dylink_basics(self):

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