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drv_hrt: added note on why an uninitialised hrt_call is safe

This commit is contained in:
Andrew Tridgell 2013-12-10 15:09:36 +11:00 committed by Lorenz Meier
parent d43e3394b0
commit cf78440ee6
1 changed files with 7 additions and 1 deletions
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8
src/drivers/stm32/drv_hrt.c
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@ -720,7 +720,6 @@ hrt_call_at(struct hrt_call *entry, hrt_abstime calltime, hrt_callout callout, v
void void
hrt_call_every(struct hrt_call *entry, hrt_abstime delay, hrt_abstime interval, hrt_callout callout, void *arg) hrt_call_every(struct hrt_call *entry, hrt_abstime delay, hrt_abstime interval, hrt_callout callout, void *arg)
{ {
hrt_call_init(entry);
hrt_call_internal(entry, hrt_call_internal(entry,
hrt_absolute_time() + delay, hrt_absolute_time() + delay,
interval, interval,
@ -734,6 +733,13 @@ hrt_call_internal(struct hrt_call *entry, hrt_abstime deadline, hrt_abstime inte
irqstate_t flags = irqsave(); irqstate_t flags = irqsave();
/* if the entry is currently queued, remove it */ /* if the entry is currently queued, remove it */
/* note that we are using a potentially uninitialised
entry->link here, but it is safe as sq_rem() doesn't
dereference the passed node unless it is found in the
list. So we potentially waste a bit of time searching the
queue for the uninitialised entry->link but we don't do
anything actually unsafe.
*/
if (entry->deadline != 0) if (entry->deadline != 0)
sq_rem(&entry->link, &callout_queue); sq_rem(&entry->link, &callout_queue);