logger watchdog: avoid using printf from IRQ context

PX4_ERR calls printf, which calls lib_sem_initialize, which calls sem_wait

src/modules/logger/watchdog.cpp

@@ -77,7 +77,9 @@ bool watchdog_update(watchdog_data_t &watchdog_data)
  watchdog_data.last_state = current_state;
 
 #if 0 // for debugging
- // test code that prints the maximum time in ready state
+ // test code that prints the maximum time in ready state.
+ // Note: we are in IRQ context, and thus are strictly speaking not allowed to use PX4_ERR -
+ // we do it anyway since it's only used for debugging.
  static uint64_t max_time = 0;
 
  if (now - watchdog_data.ready_to_run_timestamp > max_time) {
@@ -95,26 +97,18 @@ bool watchdog_update(watchdog_data_t &watchdog_data)
 #endif
 
  if (now - watchdog_data.ready_to_run_timestamp > 1_s) {
- PX4_ERR("watchdog triggered!"); // this will most likely not be logged due to dropouts
-
- // boost the priority to make sure the logger continues to write to the log
+ // boost the priority to make sure the logger continues to write to the log.
+ // Note that we never restore the priority, to keep the logic simple and because it is
+ // an event that must not occur under normal circumstances (if it does, there's a bug
+ // somewhere)
  sched_param param{};
  param.sched_priority = SCHED_PRIORITY_MAX;
- int ret;
 
  if (system_load.tasks[watchdog_data.logger_main_task_index].valid) {
- ret = sched_setparam(system_load.tasks[watchdog_data.logger_main_task_index].tcb->pid, &param);
-
- if (ret < 0) {
- PX4_ERR("sched_reprioritize failed (%i)", ret);
- }
+ sched_setparam(system_load.tasks[watchdog_data.logger_main_task_index].tcb->pid, &param);
  }
 
- ret = sched_setparam(log_writer_task.tcb->pid, &param);
-
- if (ret < 0) {
- PX4_ERR("sched_reprioritize failed (%i)", ret);
- }
+ sched_setparam(log_writer_task.tcb->pid, &param);
 
  // make sure we won't trigger again
  watchdog_data.logger_main_task_index = -1;