patacongo commented on a change in pull request #1380:
URL: https://github.com/apache/incubator-nuttx/pull/1380#discussion_r451204873
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File path: arch/arm/src/stm32f7/stm32_tickless.c
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@@ -988,22 +988,31 @@ int up_timer_start(FAR const struct timespec *ts)
}
#endif
+#ifdef CONFIG_SCHED_TICKLESS_ALARM
int up_alarm_start(FAR const struct timespec *ts)
{
uint64_t tm = ((uint64_t)ts->tv_sec * NSEC_PER_SEC + ts->tv_nsec) /
NSEC_PER_TICK;
- uint64_t counter = ((uint64_t)g_tickless.overflow << 32) |
- STM32_TIM_GETCOUNTER(g_tickless.tch);
-
- g_tickless.last_alrm = tm;
+ irqstate_t flags;
- int32_t diff = tm / NSEC_PER_TICK + counter;
+ flags = enter_critical_section();
STM32_TIM_SETCOMPARE(g_tickless.tch, CONFIG_STM32F7_TICKLESS_CHANNEL, tm);
stm32_tickless_ackint(g_tickless.channel);
stm32_tickless_enableint(CONFIG_STM32F7_TICKLESS_CHANNEL);
+ g_tickless.pending = true;
+
+ uint64_t counter = ((uint64_t)g_tickless.overflow << 32) |
+ STM32_TIM_GETCOUNTER(g_tickless.tch);
+
+ if (counter > tm)
+ {
+ stm32_interval_handler();
Review comment:
> So my change is trying to basically expire the timer before it even
starts.
The only way that I can see that happening is in sched/wdog/wd_start.c:
232 #ifdef CONFIG_SCHED_TICKLESS
233 /* Cancel the interval timer that drives the timing events. This
will
234 * cause wd_timer to be called which update the delay value for
the first
235 * time at the head of the timer list (there is a possibility that
it
236 * could even remove it).
237 */
238
239 nxsched_cancel_timer();
240 #endif
Before we set up the new interval timer, we have to cancel the current one.
But this would not effect the wdog being started at line 360 where
wd_start(0 is called; that wdog is not yet in the active wdog list. That does
not happen until after nxsched_cancel_timer(); is called.
The symptoms are different but this is very similar to the problem of issue
#1138. In that case, as I call, wd_cancel() was being called and causing an
expected timer expiration for the same reason. But the #1138 problem caused
and unexpected context switch.
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