зеркало из https://github.com/mozilla/gecko-dev.git
101 строка
3.1 KiB
Diff
101 строка
3.1 KiB
Diff
From be41a98ac222f33ed5558d86e1cede67249e99b5 Mon Sep 17 00:00:00 2001
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From: Dmitry Vyukov <dvyukov@google.com>
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Date: Sat, 21 Mar 2020 13:34:50 +0100
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Subject: [PATCH] tsan: fix deadlock with pthread_atfork callbacks
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This fixes the bug reported at:
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https://groups.google.com/forum/#!topic/thread-sanitizer/e_zB9gYqFHM
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A pthread_atfork callback triggers a data race
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and we deadlock on the report_mtx. Ignore memory access
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in the pthread_atfork callbacks to prevent the deadlock.
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---
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compiler-rt/lib/tsan/rtl/tsan_rtl.cc | 9 ++++
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.../test/tsan/pthread_atfork_deadlock2.c | 49 +++++++++++++++++++
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2 files changed, 58 insertions(+)
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create mode 100644 compiler-rt/test/tsan/pthread_atfork_deadlock2.c
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diff --git a/compiler-rt/lib/tsan/rtl/tsan_rtl.cc b/compiler-rt/lib/tsan/rtl/tsan_rtl.ccc
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index fe469faad2a2..13c9b770f50a 100644
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--- a/compiler-rt/lib/tsan/rtl/tsan_rtl.cc
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+++ b/compiler-rt/lib/tsan/rtl/tsan_rtl.cc
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@@ -495,14 +495,23 @@ int Finalize(ThreadState *thr) {
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void ForkBefore(ThreadState *thr, uptr pc) {
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ctx->thread_registry->Lock();
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ctx->report_mtx.Lock();
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+ // Ignore memory accesses in the pthread_atfork callbacks.
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+ // If any of them triggers a data race we will deadlock
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+ // on the report_mtx.
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+ // We could ignore interceptors and sync operations as well,
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+ // but so far it's unclear if it will do more good or harm.
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+ // Unnecessarily ignoring things can lead to false positives later.
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+ ThreadIgnoreBegin(thr, pc);
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}
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void ForkParentAfter(ThreadState *thr, uptr pc) {
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+ ThreadIgnoreEnd(thr, pc); // Begin is in ForkBefore.
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ctx->report_mtx.Unlock();
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ctx->thread_registry->Unlock();
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}
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void ForkChildAfter(ThreadState *thr, uptr pc) {
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+ ThreadIgnoreEnd(thr, pc); // Begin is in ForkBefore.
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ctx->report_mtx.Unlock();
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ctx->thread_registry->Unlock();
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diff --git a/compiler-rt/test/tsan/pthread_atfork_deadlock2.c b/compiler-rt/test/tsan/pthread_atfork_deadlock2.c
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new file mode 100644
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index 000000000000..700507c1e637
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--- /dev/null
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+++ b/compiler-rt/test/tsan/pthread_atfork_deadlock2.c
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@@ -0,0 +1,49 @@
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+// RUN: %clang_tsan -O1 %s -o %t && %run %t 2>&1 | FileCheck %s
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+// Regression test for
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+// https://groups.google.com/d/msg/thread-sanitizer/e_zB9gYqFHM/DmAiTsrLAwAJ
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+// pthread_atfork() callback triggers a data race and we deadlocked
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+// on the report_mtx as we lock it around fork.
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+#include "test.h"
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+#include <sys/types.h>
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+#include <sys/wait.h>
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+#include <errno.h>
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+
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+int glob = 0;
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+
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+void *worker(void *unused) {
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+ glob++;
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+ barrier_wait(&barrier);
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+ return NULL;
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+}
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+
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+void atfork() {
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+ glob++;
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+}
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+
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+int main() {
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+ barrier_init(&barrier, 2);
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+ pthread_atfork(atfork, NULL, NULL);
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+ pthread_t t;
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+ pthread_create(&t, NULL, worker, NULL);
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+ barrier_wait(&barrier);
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+ pid_t pid = fork();
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+ if (pid < 0) {
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+ fprintf(stderr, "fork failed: %d\n", errno);
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+ return 1;
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+ }
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+ if (pid == 0) {
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+ fprintf(stderr, "CHILD\n");
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+ return 0;
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+ }
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+ if (pid != waitpid(pid, NULL, 0)) {
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+ fprintf(stderr, "waitpid failed: %d\n", errno);
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+ return 1;
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+ }
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+ pthread_join(t, NULL);
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+ fprintf(stderr, "PARENT\n");
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+ return 0;
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+}
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+
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+// CHECK-NOT: ThreadSanitizer: data race
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+// CHECK: CHILD
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+// CHECK: PARENT
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