On Fri, Sep 02, 2016 at 04:29:19PM -0400, Alan Stern wrote:
> I'm afraid so. The code doesn't use wait_event(), in part because
> there's no wait_queue (since only one task is involved).
You can use wait_queue fine with just one task, and it would clean up
the code tremendously.
You can replace things like the earlier mentioned:
while (bh->state != BUF_STATE_EMPTY) {
rc = sleep_thread(common, false);
if (rc)
return rc;
}
with:
rc = wait_event_interruptible(&common->wq, bh->state ==
BUF_STATE_EMPTY);
if (rc)
return rc;
> But maybe there's another barrier which needs to be fixed. Felipe, can
> you check to see if received_cbw() is getting called in
> get_next_command(), and if so, what value it returns? Or is the
> preceding sleep_thread() the one that never wakes up?
>
> It could be that the smp_wmb() in wakeup_thread() needs to be smp_mb().
> The reason being that get_next_command() runs outside the protection of
> the spinlock.
Being somewhat confused by the code, I fail to follow that argument.
wakeup_thread() is always called under that spinlock(), but since the
critical section is 2 stores, I fail to see how a smp_mb() can make any
difference over the smp_wmb() already there.
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