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px4io mixer: fix atomic access to system_state.fmu_data_received_time

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system_state.fmu_data_received_time can be set from an IRQ handler, thus
we need to ensure every read access to it in mixer_tick is atomic.
So we read it once and copy it into a local variable.
This commit is contained in:
Beat Küng 2019-01-23 15:19:40 +01:00
parent 74a3c378b2
commit 3859bbb3b0
1 changed files with 8 additions and 4 deletions
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12
src/modules/px4iofirmware/mixer.cpp
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@ -118,8 +118,12 @@ mixer_tick(void)
mixer_handle_text_create_mixer();
/* check that we are receiving fresh data from the FMU */
if ((system_state.fmu_data_received_time == 0) ||
hrt_elapsed_time_atomic(&system_state.fmu_data_received_time) > FMU_INPUT_DROP_LIMIT_US) {
irqstate_t irq_flags = enter_critical_section();
const hrt_abstime fmu_data_received_time = system_state.fmu_data_received_time;
leave_critical_section(irq_flags);
if ((fmu_data_received_time == 0) ||
hrt_elapsed_time(&fmu_data_received_time) > FMU_INPUT_DROP_LIMIT_US) {
/* too long without FMU input, time to go to failsafe */
if (r_status_flags & PX4IO_P_STATUS_FLAGS_FMU_OK) {
@ -135,9 +139,9 @@ mixer_tick(void)
/* this flag is never cleared once OK */
PX4_ATOMIC_MODIFY_OR(r_status_flags, PX4IO_P_STATUS_FLAGS_FMU_INITIALIZED);
if (system_state.fmu_data_received_time > last_fmu_update) {
if (fmu_data_received_time > last_fmu_update) {
new_fmu_data = true;
last_fmu_update = system_state.fmu_data_received_time;
last_fmu_update = fmu_data_received_time;
}
}