logging: Introduce mutex API to manage log_target in multi-thread envs

log_enable_multithread() enables use of locks inside the
implementation. Lock use is disabled by default, this way only
multi-thread processes need to enable it and suffer related
complexity/performance penalties.

Locks are required around osmo_log_target_list and items inside it,
since targets can be used, modified and deleted by different threads
concurrently (for instance, user writing "logging disable" in VTY while
another thread is willing to write into that target).

Multithread apps and libraries aiming at being used in multithread apps
should update their code to use the locks introduced here when
containing code iterating over osmo_log_target_list explictly or
implicitly by obtaining a log_target (eg. osmo_log_vty2tgt()).

Related: OS#4088
Change-Id: Id7711893b34263baacac6caf4d489467053131bb

1 files changed, 8 insertions, 2 deletions

diff --git a/src/gb/gprs_ns_vty.c b/src/gb/gprs_ns_vty.c
index 53c71a9a..4a904368 100644
--- a/src/gb/gprs_ns_vty.c
+++ b/src/gb/gprs_ns_vty.c
@@ -587,12 +587,16 @@ DEFUN(logging_fltr_nsvc,
 	"Identify NS-VC by NSVCI\n"
 	"Numeric identifier\n")
 {
-	struct log_target *tgt = osmo_log_vty2tgt(vty);
+	struct log_target *tgt;
 	struct gprs_nsvc *nsvc;
 	uint16_t id = atoi(argv[1]);
 
-	if (!tgt)
+	log_tgt_mutex_lock();
+	tgt = osmo_log_vty2tgt(vty);
+	if (!tgt) {
+		log_tgt_mutex_unlock();
 		return CMD_WARNING;
+	}
 
 	if (!strcmp(argv[0], "nsei"))
 		nsvc = gprs_nsvc_by_nsei(vty_nsi, id);
@@ -601,10 +605,12 @@ DEFUN(logging_fltr_nsvc,
 
 	if (!nsvc) {
 		vty_out(vty, "No NS-VC by that identifier%s", VTY_NEWLINE);
+		log_tgt_mutex_unlock();
 		return CMD_WARNING;
 	}
 
 	log_set_nsvc_filter(tgt, nsvc);
+	log_tgt_mutex_unlock();
 	return CMD_SUCCESS;
 }