mirror of
https://github.com/jart/cosmopolitan.git
synced 2025-02-24 23:09:02 +00:00
af7bd80430
This change introduces a new deadlock detector for Cosmo's POSIX threads implementation. Error check mutexes will now track a DAG of nested locks and report EDEADLK when a deadlock is theoretically possible. These will occur rarely, but it's important for production hardening your code. You don't even need to change your mutexes to use the POSIX error check mode because `cosmocc -mdbg` will enable error checking on mutexes by default globally. When cycles are found, an error message showing your demangled symbols describing the strongly connected component are printed and then the SIGTRAP is raised, which means you'll also get a backtrace if you're using ShowCrashReports() too. This new error checker is so low-level and so pure that it's able to verify the relationships of every libc runtime lock, including those locks upon which the mutex implementation depends.
239 lines
8.6 KiB
C
239 lines
8.6 KiB
C
/*-*- mode:c;indent-tabs-mode:nil;c-basic-offset:2;tab-width:8;coding:utf-8 -*-│
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│ vi: set et ft=c ts=2 sts=2 sw=2 fenc=utf-8 :vi │
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╞══════════════════════════════════════════════════════════════════════════════╡
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│ Copyright 2022 Justine Alexandra Roberts Tunney │
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│ │
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│ Permission to use, copy, modify, and/or distribute this software for │
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│ any purpose with or without fee is hereby granted, provided that the │
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│ above copyright notice and this permission notice appear in all copies. │
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│ │
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│ THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL │
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│ WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED │
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│ WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE │
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│ AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL │
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│ DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR │
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│ PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER │
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│ TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR │
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│ PERFORMANCE OF THIS SOFTWARE. │
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╚─────────────────────────────────────────────────────────────────────────────*/
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#include "libc/atomic.h"
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#include "libc/calls/calls.h"
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#include "libc/calls/struct/sigaction.h"
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#include "libc/calls/struct/timespec.h"
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#include "libc/errno.h"
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#include "libc/fmt/itoa.h"
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#include "libc/fmt/magnumstrs.internal.h"
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#include "libc/intrin/atomic.h"
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#include "libc/intrin/kprintf.h"
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#include "libc/intrin/weaken.h"
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#include "libc/runtime/internal.h"
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#include "libc/runtime/runtime.h"
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#include "libc/runtime/stack.h"
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#include "libc/runtime/symbols.internal.h"
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#include "libc/str/str.h"
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#include "libc/sysv/consts/clone.h"
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#include "libc/sysv/consts/sig.h"
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#include "libc/thread/thread.h"
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#include "libc/thread/tls.h"
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#include "third_party/nsync/mu.h"
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/**
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* @fileoverview Austere Mutex Test
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*
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* 1. Tests what happens when *NSYNC isn't linked.
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* 2. Tests what happens when TLS isn't enabled.
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*
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* If either:
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*
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* 1. malloc() isn't linked, or
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* 2. we're in MODE=tiny
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*
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* Then we use Cosmopolitan's hand-rolled tiny locks. They're not
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* scalable. They use a lot of CPU if you have lots of threads. But
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* they're wicked fast and free of bloat if your app is tiny.
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*/
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atomic_int ready;
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atomic_int counter;
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atomic_int success;
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pthread_mutex_t mu;
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#define ASSERT_EQ(WANT, GOT) \
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do { \
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long _want = WANT, _got = GOT; \
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if (_want != _got) \
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__assert_eq_fail(__FILE__, __LINE__, #WANT, #GOT, _want, _got); \
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} while (0)
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void ignore_signal(int sig) {
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}
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void __assert_eq_fail(const char *file, int line, const char *wantstr,
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const char *gotstr, long want, long got) {
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kprintf("%s:%d: %s vs. %s was %ld vs. %ld (%s)\n", file, line, wantstr,
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gotstr, want, got, !(got & ~255) ? _strerrno(got) : "n/a");
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_Exit(1);
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}
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double time2dbl(struct timespec t) {
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return (((double)t.tv_sec) + ((double)t.tv_nsec * 1e-9));
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}
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char *time2str(double s) {
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static char buf[32];
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static const struct {
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const char *suffix;
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double multiplier;
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} scale[] = {
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{"ns", 1.0e-9}, //
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{"us", 1e-6}, //
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{"ms", 1e-3}, //
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{"s", 1.0}, //
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{"hr", 3600.0}, //
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};
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int i = 0;
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while (i + 1 != sizeof(scale) / sizeof(scale[0]) &&
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scale[i + 1].multiplier <= s) {
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i++;
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}
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stpcpy(FormatInt32(buf, s / scale[i].multiplier), scale[i].suffix);
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return buf;
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}
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int Worker(void *arg) {
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int i, x;
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atomic_store(&ready, 1);
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for (i = 0; i < 10000; ++i) {
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ASSERT_EQ(0, pthread_mutex_lock(&mu));
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x = atomic_load_explicit(&counter, memory_order_relaxed);
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atomic_store_explicit(&counter, x + 1, memory_order_relaxed);
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ASSERT_EQ(x + 1, atomic_load_explicit(&counter, memory_order_relaxed));
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ASSERT_EQ(0, pthread_mutex_unlock(&mu));
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}
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atomic_store(&success, 1);
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return 0;
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}
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void TestContendedLock(const char *name, int kind) {
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char *stk;
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double ns;
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errno_t rc;
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struct timespec t1, t2;
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pthread_mutexattr_t attr;
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int tid, x, i, n = 10000;
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struct CosmoTib tib = {.tib_self = &tib, .tib_self2 = &tib, .tib_tid = -1};
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pthread_mutexattr_init(&attr);
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pthread_mutexattr_settype(&attr, kind);
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pthread_mutex_init(&mu, &attr);
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pthread_mutexattr_destroy(&attr);
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atomic_store(&ready, 0);
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atomic_store(&success, 0);
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stk = NewCosmoStack();
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rc = clone(Worker, stk, GetStackSize() - 16 /* openbsd:stackbound */,
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CLONE_VM | CLONE_THREAD | CLONE_FS | CLONE_FILES | CLONE_SIGHAND |
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CLONE_SYSVSEM | CLONE_PARENT_SETTID | CLONE_CHILD_SETTID |
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CLONE_CHILD_CLEARTID | CLONE_SETTLS,
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0, &tid, &tib, &tib.tib_tid);
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if (rc) {
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kprintf("clone failed: %s\n", strerror(rc));
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_Exit(1);
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}
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while (!atomic_load(&ready))
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donothing;
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t1 = timespec_real();
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for (i = 0; i < n; ++i) {
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ASSERT_EQ(0, pthread_mutex_lock(&mu));
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x = atomic_load_explicit(&counter, memory_order_relaxed);
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atomic_store_explicit(&counter, x - 1, memory_order_relaxed);
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ASSERT_EQ(x - 1, atomic_load_explicit(&counter, memory_order_relaxed));
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ASSERT_EQ(0, pthread_mutex_unlock(&mu));
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}
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t2 = timespec_real();
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while (tib.tib_tid)
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donothing;
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ASSERT_EQ(1, atomic_load(&success));
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ASSERT_EQ(0, atomic_load(&counter));
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FreeCosmoStack(stk);
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ASSERT_EQ(0, pthread_mutex_destroy(&mu));
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ns = time2dbl(timespec_sub(t2, t1)) / n;
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kprintf("%s contended took %s\n", name, time2str(ns));
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}
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void TestUncontendedLock(const char *name, int kind) {
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double ns;
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long i, n = 10000;
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struct timespec t1, t2;
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pthread_mutex_t lock;
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pthread_mutexattr_t attr;
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pthread_mutexattr_init(&attr);
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pthread_mutexattr_settype(&attr, kind);
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pthread_mutex_init(&lock, &attr);
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pthread_mutexattr_destroy(&attr);
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t1 = timespec_real();
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for (i = 0; i < n; ++i) {
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pthread_mutex_lock(&lock);
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pthread_mutex_unlock(&lock);
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}
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t2 = timespec_real();
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pthread_mutex_destroy(&lock);
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ns = time2dbl(timespec_sub(t2, t1)) / n;
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kprintf("%s took %s\n", name, time2str(ns));
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}
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int main(int argc, char *argv[]) {
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pthread_mutexattr_t attr;
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#ifdef MODE_DBG
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GetSymbolTable();
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signal(SIGTRAP, ignore_signal);
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kprintf("running %s\n", argv[0]);
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#endif
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#ifdef __aarch64__
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// our usage of raw clone() is probably broken in aarch64
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// we should just get rid of clone()
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if (1)
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return 0;
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#endif
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if (_weaken(nsync_mu_lock)) {
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kprintf("*NSYNC should not be linked\n");
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_Exit(1);
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}
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ASSERT_EQ(0, pthread_mutexattr_init(&attr));
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ASSERT_EQ(0, pthread_mutexattr_settype(&attr, PTHREAD_MUTEX_DEFAULT));
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ASSERT_EQ(0, pthread_mutex_init(&mu, &attr));
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ASSERT_EQ(0, pthread_mutexattr_destroy(&attr));
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ASSERT_EQ(0, pthread_mutex_lock(&mu));
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ASSERT_EQ(0, pthread_mutex_unlock(&mu));
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ASSERT_EQ(0, pthread_mutex_destroy(&mu));
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ASSERT_EQ(0, pthread_mutexattr_init(&attr));
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ASSERT_EQ(0, pthread_mutexattr_settype(&attr, PTHREAD_MUTEX_RECURSIVE));
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ASSERT_EQ(0, pthread_mutex_init(&mu, &attr));
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ASSERT_EQ(0, pthread_mutexattr_destroy(&attr));
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ASSERT_EQ(0, pthread_mutex_lock(&mu));
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ASSERT_EQ(0, pthread_mutex_lock(&mu));
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ASSERT_EQ(0, pthread_mutex_unlock(&mu));
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ASSERT_EQ(0, pthread_mutex_unlock(&mu));
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ASSERT_EQ(0, pthread_mutex_destroy(&mu));
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ASSERT_EQ(0, pthread_mutexattr_init(&attr));
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ASSERT_EQ(0, pthread_mutexattr_settype(&attr, PTHREAD_MUTEX_ERRORCHECK));
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ASSERT_EQ(0, pthread_mutex_init(&mu, &attr));
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ASSERT_EQ(0, pthread_mutexattr_destroy(&attr));
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ASSERT_EQ(0, pthread_mutex_lock(&mu));
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ASSERT_EQ(EDEADLK, pthread_mutex_lock(&mu));
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ASSERT_EQ(0, pthread_mutex_unlock(&mu));
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ASSERT_EQ(0, pthread_mutex_destroy(&mu));
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TestUncontendedLock("PTHREAD_MUTEX_DEFAULT RAW TLS", PTHREAD_MUTEX_DEFAULT);
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TestUncontendedLock("PTHREAD_MUTEX_RECURSIVE RAW TLS",
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PTHREAD_MUTEX_RECURSIVE);
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TestContendedLock("PTHREAD_MUTEX_DEFAULT RAW TLS", PTHREAD_MUTEX_DEFAULT);
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TestContendedLock("PTHREAD_MUTEX_RECURSIVE RAW TLS", PTHREAD_MUTEX_RECURSIVE);
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//
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}
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