[ovs-dev] [threads 22/23] fatal-signal: Make thread-safe.
Ben Pfaff
blp at nicira.com
Thu Jul 18 23:15:35 UTC 2013
Signed-off-by: Ben Pfaff <blp at nicira.com>
---
lib/fatal-signal.c | 56 +++++++++++++++++++++++++++++++++++++++++++--------
lib/fatal-signal.h | 3 +-
lib/ovs-thread.c | 5 ++++
lib/ovs-thread.h | 6 +++++
4 files changed, 60 insertions(+), 10 deletions(-)
diff --git a/lib/fatal-signal.c b/lib/fatal-signal.c
index db8d98e..40daf5a 100644
--- a/lib/fatal-signal.c
+++ b/lib/fatal-signal.c
@@ -23,6 +23,7 @@
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
+#include "ovs-thread.h"
#include "poll-loop.h"
#include "shash.h"
#include "sset.h"
@@ -56,20 +57,32 @@ static size_t n_hooks;
static int signal_fds[2];
static volatile sig_atomic_t stored_sig_nr = SIG_ATOMIC_MAX;
-static void fatal_signal_init(void);
+static pthread_mutex_t mutex;
+
static void atexit_handler(void);
static void call_hooks(int sig_nr);
-static void
+/* Initializes the fatal signal handling module. Calling this function is
+ * optional, because calling any other function in the module will also
+ * initialize it. However, in a multithreaded program, the module must be
+ * initialized while the process is still single-threaded. */
+void
fatal_signal_init(void)
{
static bool inited = false;
if (!inited) {
+ pthread_mutexattr_t attr;
size_t i;
+ assert_single_threaded();
inited = true;
+ xpthread_mutexattr_init(&attr);
+ xpthread_mutexattr_settype(&attr, PTHREAD_MUTEX_RECURSIVE);
+ xpthread_mutex_init(&mutex, &attr);
+ xpthread_mutexattr_destroy(&attr);
+
xpipe_nonblocking(signal_fds);
for (i = 0; i < ARRAY_SIZE(fatal_signals); i++) {
@@ -86,13 +99,13 @@ fatal_signal_init(void)
}
}
-/* Registers 'hook_cb' to be called when a process termination signal is
- * raised. If 'run_at_exit' is true, 'hook_cb' is also called during normal
- * process termination, e.g. when exit() is called or when main() returns.
+/* Registers 'hook_cb' to be called from inside poll_block() following a fatal
+ * signal. 'hook_cb' does not need to be async-signal-safe. In a
+ * multithreaded program 'hook_cb' might be called from any thread, with
+ * threads other than the one running 'hook_cb' in unknown states.
*
- * 'hook_cb' is not called immediately from the signal handler but rather the
- * next time the poll loop iterates, so it is freed from the usual restrictions
- * on signal handler functions.
+ * If 'run_at_exit' is true, 'hook_cb' is also called during normal process
+ * termination, e.g. when exit() is called or when main() returns.
*
* If the current process forks, fatal_signal_fork() may be called to clear the
* parent process's fatal signal hooks, so that 'hook_cb' is only called when
@@ -106,12 +119,14 @@ fatal_signal_add_hook(void (*hook_cb)(void *aux), void (*cancel_cb)(void *aux),
{
fatal_signal_init();
+ xpthread_mutex_lock(&mutex);
ovs_assert(n_hooks < MAX_HOOKS);
hooks[n_hooks].hook_cb = hook_cb;
hooks[n_hooks].cancel_cb = cancel_cb;
hooks[n_hooks].aux = aux;
hooks[n_hooks].run_at_exit = run_at_exit;
n_hooks++;
+ xpthread_mutex_unlock(&mutex);
}
/* Handles fatal signal number 'sig_nr'.
@@ -152,6 +167,8 @@ fatal_signal_run(void)
if (sig_nr != SIG_ATOMIC_MAX) {
char namebuf[SIGNAL_NAME_BUFSIZE];
+ xpthread_mutex_lock(&mutex);
+
VLOG_WARN("terminating with signal %d (%s)",
(int)sig_nr, signal_name(sig_nr, namebuf, sizeof namebuf));
call_hooks(sig_nr);
@@ -160,6 +177,9 @@ fatal_signal_run(void)
* termination status reflects that we were killed by this signal */
signal(sig_nr, SIG_DFL);
raise(sig_nr);
+
+ xpthread_mutex_unlock(&mutex);
+ NOT_REACHED();
}
}
@@ -210,12 +230,16 @@ static void do_unlink_files(void);
void
fatal_signal_add_file_to_unlink(const char *file)
{
+ fatal_signal_init();
+
+ xpthread_mutex_lock(&mutex);
if (!added_hook) {
added_hook = true;
fatal_signal_add_hook(unlink_files, cancel_files, NULL, true);
}
sset_add(&files, file);
+ xpthread_mutex_unlock(&mutex);
}
/* Unregisters 'file' from being unlinked when the program terminates via
@@ -223,7 +247,11 @@ fatal_signal_add_file_to_unlink(const char *file)
void
fatal_signal_remove_file_to_unlink(const char *file)
{
+ fatal_signal_init();
+
+ xpthread_mutex_lock(&mutex);
sset_find_and_delete(&files, file);
+ xpthread_mutex_unlock(&mutex);
}
/* Like fatal_signal_remove_file_to_unlink(), but also unlinks 'file'.
@@ -231,13 +259,21 @@ fatal_signal_remove_file_to_unlink(const char *file)
int
fatal_signal_unlink_file_now(const char *file)
{
- int error = unlink(file) ? errno : 0;
+ int error;
+
+ fatal_signal_init();
+
+ xpthread_mutex_lock(&mutex);
+
+ error = unlink(file) ? errno : 0;
if (error) {
VLOG_WARN("could not unlink \"%s\" (%s)", file, ovs_strerror(error));
}
fatal_signal_remove_file_to_unlink(file);
+ xpthread_mutex_unlock(&mutex);
+
return error;
}
@@ -277,6 +313,8 @@ fatal_signal_fork(void)
{
size_t i;
+ assert_single_threaded();
+
for (i = 0; i < n_hooks; i++) {
struct hook *h = &hooks[i];
if (h->cancel_cb) {
diff --git a/lib/fatal-signal.h b/lib/fatal-signal.h
index 8a1a84b..b458d3d 100644
--- a/lib/fatal-signal.h
+++ b/lib/fatal-signal.h
@@ -1,5 +1,5 @@
/*
- * Copyright (c) 2008, 2009, 2010 Nicira, Inc.
+ * Copyright (c) 2008, 2009, 2010, 2013 Nicira, Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
@@ -20,6 +20,7 @@
#include <stdbool.h>
/* Basic interface. */
+void fatal_signal_init(void);
void fatal_signal_add_hook(void (*hook_cb)(void *aux),
void (*cancel_cb)(void *aux), void *aux,
bool run_at_exit);
diff --git a/lib/ovs-thread.c b/lib/ovs-thread.c
index d08751c..4776587 100644
--- a/lib/ovs-thread.c
+++ b/lib/ovs-thread.c
@@ -77,6 +77,11 @@ XPTHREAD_FUNC1(pthread_mutex_lock, pthread_mutex_t *);
XPTHREAD_FUNC1(pthread_mutex_unlock, pthread_mutex_t *);
XPTHREAD_TRY_FUNC1(pthread_mutex_trylock, pthread_mutex_t *);
+XPTHREAD_FUNC1(pthread_mutexattr_init, pthread_mutexattr_t *);
+XPTHREAD_FUNC1(pthread_mutexattr_destroy, pthread_mutexattr_t *);
+XPTHREAD_FUNC2(pthread_mutexattr_settype, pthread_mutexattr_t *, int);
+XPTHREAD_FUNC2(pthread_mutexattr_gettype, pthread_mutexattr_t *, int *);
+
XPTHREAD_FUNC2(pthread_rwlock_init,
pthread_rwlock_t *, pthread_rwlockattr_t *);
XPTHREAD_FUNC1(pthread_rwlock_rdlock, pthread_rwlock_t *);
diff --git a/lib/ovs-thread.h b/lib/ovs-thread.h
index 9c8023e..b18447d 100644
--- a/lib/ovs-thread.h
+++ b/lib/ovs-thread.h
@@ -56,11 +56,17 @@
* process with an error message on any error. The *_trylock() functions are
* exceptions: they pass through a 0 or EBUSY return value to the caller and
* abort on any other error. */
+
void xpthread_mutex_init(pthread_mutex_t *, pthread_mutexattr_t *);
void xpthread_mutex_lock(pthread_mutex_t *mutex) OVS_ACQUIRES(mutex);
void xpthread_mutex_unlock(pthread_mutex_t *mutex) OVS_RELEASES(mutex);
int xpthread_mutex_trylock(pthread_mutex_t *);
+void xpthread_mutexattr_init(pthread_mutexattr_t *);
+void xpthread_mutexattr_destroy(pthread_mutexattr_t *);
+void xpthread_mutexattr_settype(pthread_mutexattr_t *, int type);
+void xpthread_mutexattr_gettype(pthread_mutexattr_t *, int *typep);
+
void xpthread_rwlock_init(pthread_rwlock_t *, pthread_rwlockattr_t *);
void xpthread_rwlock_rdlock(pthread_rwlock_t *rwlock) OVS_ACQUIRES(rwlock);
void xpthread_rwlock_wrlock(pthread_rwlock_t *rwlock) OVS_ACQUIRES(rwlock);
--
1.7.2.5
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