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[mavlink] Use separate mutex for event buffer to prevent deadlock #22225

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merged 1 commit into from
Oct 17, 2023
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[mavlink] Use separate mutex for event buffer to prevent deadlock #22225

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21 changes: 14 additions & 7 deletions src/modules/mavlink/mavlink_main.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -81,6 +81,7 @@
#define MAIN_LOOP_DELAY 10000 ///< 100 Hz @ 1000 bytes/s data rate

static pthread_mutex_t mavlink_module_mutex = PTHREAD_MUTEX_INITIALIZER;
static pthread_mutex_t mavlink_event_buffer_mutex = PTHREAD_MUTEX_INITIALIZER;
events::EventBuffer *Mavlink::_event_buffer = nullptr;

Mavlink *mavlink_module_instances[MAVLINK_COMM_NUM_BUFFERS] {};
Expand Down Expand Up @@ -375,15 +376,21 @@ Mavlink::destroy_all_instances()
}
}

LockGuard lg{mavlink_module_mutex};
{
LockGuard lg{mavlink_module_mutex};

// we know all threads have exited, so it's safe to delete objects.
for (Mavlink *inst_to_del : mavlink_module_instances) {
delete inst_to_del;
// we know all threads have exited, so it's safe to delete objects.
for (Mavlink *inst_to_del : mavlink_module_instances) {
delete inst_to_del;
}
}

delete _event_buffer;
_event_buffer = nullptr;
{
LockGuard lg{mavlink_event_buffer_mutex};

delete _event_buffer;
_event_buffer = nullptr;
}

PX4_INFO("all instances stopped");
return OK;
Expand Down Expand Up @@ -2543,7 +2550,7 @@ Mavlink::task_main(int argc, char *argv[])
/* handle new events */
if (check_events()) {
if (_event_sub.updated()) {
LockGuard lg{mavlink_module_mutex};
LockGuard lg{mavlink_event_buffer_mutex};

event_s orb_event;

Expand Down