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In queue_wait_w_tmo, guarantee wait duration

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It is possible to have a thread awoken and subsequently the message
that was placed in the queue has been removed by the time the thread
is able to check the queue. Ensure theads that failed to find a
message do not return prematurely.

It was at worst imprecise when a timeout is specified. It's entirely
incorrect if the function ever returns with SYS_TIMEOUT when using
TIMEOUT_BLOCK.

Change-Id: Ibd41eae8c787adf7a320a24603cf64ff8a6da66a
This commit is contained in:
Michael Sevakis 2017-02-02 16:06:25 -05:00
parent 1fa7c56351
commit 4d4b0c5a07
2 changed files with 41 additions and 22 deletions
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40
firmware/kernel/queue.c
View file

@ -339,9 +339,6 @@ void queue_wait_w_tmo(struct event_queue *q, struct queue_event *ev, int ticks)
oldlevel = disable_irq_save();
if (ticks != TIMEOUT_NOBLOCK)
ASSERT_CPU_MODE(CPU_MODE_THREAD_CONTEXT, oldlevel);
corelock_lock(&q->cl);
#ifdef HAVE_EXTENDED_MESSAGING_AND_NAME
@ -351,12 +348,17 @@ void queue_wait_w_tmo(struct event_queue *q, struct queue_event *ev, int ticks)
rd = q->read;
wr = q->write;
if (rd == wr && ticks != 0)
if(rd != wr || ticks == 0)
; /* no block */
else while(1)
{
ASSERT_CPU_MODE(CPU_MODE_THREAD_CONTEXT, oldlevel);
struct thread_entry *current = __running_self_entry();
block_thread(current, ticks, &q->queue, NULL);
corelock_unlock(&q->cl);
corelock_unlock(&q->cl);
switch_thread();
disable_irq();
@ -365,29 +367,41 @@ void queue_wait_w_tmo(struct event_queue *q, struct queue_event *ev, int ticks)
rd = q->read;
wr = q->write;
wait_queue_try_remove(current);
if(rd != wr)
break;
if(ticks < 0)
continue; /* empty again, infinite block */
/* timeout is legit if thread is still queued and awake */
if(LIKELY(wait_queue_try_remove(current)))
break;
/* we mustn't return earlier than expected wait time */
ticks = get_tmo_tick(current) - current_tick;
if(ticks <= 0)
break;
}
#ifdef HAVE_EXTENDED_MESSAGING_AND_NAME
if(ev)
if(UNLIKELY(!ev))
; /* just waiting for something */
else
#endif
{
/* no worry about a removed message here - status is checked inside
locks - perhaps verify if timeout or false alarm */
if (rd != wr)
if(rd != wr)
{
q->read = rd + 1;
rd &= QUEUE_LENGTH_MASK;
*ev = q->events[rd];
/* Get data for a waiting thread if one */
queue_do_fetch_sender(q->send, rd);
}
else
{
ev->id = SYS_TIMEOUT;
ev->data = 0;
}
}
/* else just waiting on non-empty */
corelock_unlock(&q->cl);
restore_irq(oldlevel);

5
firmware/kernel/thread-internal.h
View file

@ -419,4 +419,9 @@ static inline void blocker_splay_init(struct blocker_splay *blsplay)
corelock_init(&blsplay->cl);
}
static inline long get_tmo_tick(struct thread_entry *thread)
{
return thread->tmo_tick;
}
#endif /* THREAD_INTERNAL_H */