X-Git-Url: http://git.lttng.org/?a=blobdiff_plain;f=libust%2Flttng-ust-comm.c;h=1e4031be273fcbcc7a29d397ab0bb8db3bbcfa22;hb=e822f505be95ac8c30c7b535a7b48c05ed0c1293;hp=0f7bc34b6ed14200af50f44731c89ca1ee1a4457;hpb=74d89c32c1f8928943e1ce7eae5d659d4fd601a9;p=lttng-ust.git

diff --git a/libust/lttng-ust-comm.c b/libust/lttng-ust-comm.c
index 0f7bc34b..1e4031be 100644
--- a/libust/lttng-ust-comm.c
+++ b/libust/lttng-ust-comm.c
@@ -28,6 +28,7 @@
 #include <semaphore.h>
 #include <time.h>
 #include <assert.h>
+#include <signal.h>
 #include <urcu/uatomic.h>
 
 #include <lttng-ust-comm.h>
@@ -35,6 +36,7 @@
 #include <ust/lttng-ust-abi.h>
 #include <ust/tracepoint.h>
 #include <ust/tracepoint-internal.h>
+#include <ust/ust.h>
 
 /*
  * Has lttng ust comm constructor been called ?
@@ -541,3 +543,58 @@ void __attribute__((destructor)) lttng_ust_exit(void)
 	ltt_ring_buffer_metadata_client_exit();
 	exit_tracepoint();
 }
+
+/*
+ * We exclude the worker threads across fork and clone (except
+ * CLONE_VM), because these system calls only keep the forking thread
+ * running in the child.  Therefore, we don't want to call fork or clone
+ * in the middle of an tracepoint or ust tracing state modification.
+ * Holding this mutex protects these structures across fork and clone.
+ */
+void ust_before_fork(ust_fork_info_t *fork_info)
+{
+	/*
+	 * Disable signals. This is to avoid that the child intervenes
+	 * before it is properly setup for tracing. It is safer to
+	 * disable all signals, because then we know we are not breaking
+	 * anything by restoring the original mask.
+         */
+	sigset_t all_sigs;
+	int ret;
+
+	/* Disable signals */
+	sigfillset(&all_sigs);
+	ret = sigprocmask(SIG_BLOCK, &all_sigs, &fork_info->orig_sigs);
+	if (ret == -1) {
+		PERROR("sigprocmask");
+	}
+	pthread_mutex_lock(&lttng_ust_comm_mutex);
+	rcu_bp_before_fork();
+}
+
+static void ust_after_fork_common(ust_fork_info_t *fork_info)
+{
+	int ret;
+
+	pthread_mutex_unlock(&lttng_ust_comm_mutex);
+	/* Restore signals */
+	ret = sigprocmask(SIG_SETMASK, &fork_info->orig_sigs, NULL);
+	if (ret == -1) {
+		PERROR("sigprocmask");
+	}
+}
+
+void ust_after_fork_parent(ust_fork_info_t *fork_info)
+{
+	rcu_bp_after_fork_parent();
+	/* Release mutexes and reenable signals */
+	ust_after_fork_common(fork_info);
+}
+
+void ust_after_fork_child(ust_fork_info_t *fork_info)
+{
+	/* Release urcu mutexes */
+	rcu_bp_after_fork_child();
+	/* Release mutexes and reenable signals */
+	ust_after_fork_common(fork_info);
+}