From 4e4714cb244d7ace4f4a462a3923066fd4760669 Mon Sep 17 00:00:00 2001 From: Jonathan Rajotte Date: Thu, 3 Sep 2015 17:48:36 -0400 Subject: [PATCH] Fix: race between kconsumerd and sessiond on tear down MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit v2: minimize indentation by using return on condition. Kconsumerd and sessiond both have reference on lttng-module. This can lead to a race on modprobe_remove_lttng_all which might fail to unload modules due to certain modules not having a ref count equal to zero at the time. waitpid is used to force a synchronization on the child (kconsumer) termination. This also have been applied to ust consumers for the sake of consistency. Fixes: #878 Signed-off-by: Jonathan Rajotte Signed-off-by: Jérémie Galarneau --- src/bin/lttng-sessiond/main.c | 34 +++++++++++++++++++++++++++++++++- 1 file changed, 33 insertions(+), 1 deletion(-) diff --git a/src/bin/lttng-sessiond/main.c b/src/bin/lttng-sessiond/main.c index d4dae16fd..2983cbf8c 100644 --- a/src/bin/lttng-sessiond/main.c +++ b/src/bin/lttng-sessiond/main.c @@ -586,6 +586,34 @@ static int generate_lock_file_path(char *path, size_t len) return ret; } +/* + * Wait on consumer process termination. + * + * Need to be called with the consumer data lock held or from a context + * ensuring no concurrent access to data (e.g: cleanup). + */ +static void wait_consumer(struct consumer_data *consumer_data) +{ + pid_t ret; + int status; + + if (consumer_data->pid <= 0) { + return; + } + + DBG("Waiting for complete teardown of consumerd (PID: %d)", + consumer_data->pid); + ret = waitpid(consumer_data->pid, &status, 0); + if (ret == -1) { + PERROR("consumerd waitpid pid: %d", consumer_data->pid) + } + if (!WIFEXITED(status)) { + ERR("consumerd termination with error: %d", + WEXITSTATUS(ret)); + } + consumer_data->pid = 0; +} + /* * Cleanup the session daemon's data structures. */ @@ -680,6 +708,11 @@ static void sessiond_cleanup(void) } } + wait_consumer(&kconsumer_data); + wait_consumer(&ustconsumer64_data); + wait_consumer(&ustconsumer32_data); + + DBG("Cleaning up all agent apps"); agent_app_ht_clean(); @@ -1500,7 +1533,6 @@ error: unlink(consumer_data->err_unix_sock_path); unlink(consumer_data->cmd_unix_sock_path); - consumer_data->pid = 0; pthread_mutex_unlock(&consumer_data->lock); /* Cleanup metadata socket mutex. */ -- 2.34.1