Bartlomiej Zolnierkiewicz wrote:
> On Wed, 24 Jul 2002, Jens Axboe wrote:
>
>
>>On Wed, Jul 24 2002, Marcin Dalecki wrote:
>>
>>>>Jens, the same is in cciss.c.
>>>>Please remove locking from blk_stop_queue() (as you suggested) or intrduce
>>>>unlocking in request_functions.
>>>>
>>>
>>>Bartek I think the removal is just for reassertion that the
>>>locking is the problem. You can't remove it easly from
>>>blk_stop_queue() unless you make it mandatory that blk_stop_queue
>>>has to be run with the lock already held. Or in other words
>>>basically -> Don't use blk_stop_queue() outside of ->request_fn.
>>
>>Of couse Bart is advocating just making sure that every caller of
>>blk_stop_queue() _has_ the queue_lock before calling it, not removing
>>the locking there.
>>
>>--
>>Jens Axboe
>
>
> And I'm also advocating for __blk_start_queue() ideal for usage in
> ata_end_request(). And moving spin_lock scope to cover test_and_set_bit()
> in blk_start_queue() (for coherency and avoiding spurious calls to
> q->request_fn() )
You mean this:
void blk_start_queue(request_queue_t *q)
{
if (test_bit(QUEUE_FLAG_STOPPED, &q->queue_flags)) {
unsigned long flags;
spin_lock_irqsave(q->queue_lock, flags);
if (!test_bit(QUEUE_FLAG_STOPPED, &q->queue_flags)) {
spin_unlock_irqrestore(q->queue_lock, flags);
return;
}
clear_bit(QUEUE_FLAG_STOPPED, &q->queue_flags);
if (!elv_queue_empty(q))
q->request_fn(q);
spin_unlock_irqrestore(q->queue_lock, flags);
}
}
Becouse this is avoiding checking for spinlock in the case
the queue is not stopped.
The spinlock free variant isn't needed right.
> However IDE_BUSY -> QUEUE_STOPPED_FLAG is braindamaged idea.
You should never see it. Think of it as a mind bridge between
IDE_BUSY and queue plug and unplug please. Becouse the purpose
of IDE_BUSY *is* to effectively stall queue processing for
the time of internally issued request. OK?
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This archive was generated by hypermail 2b29 : Tue Jul 30 2002 - 14:00:16 EST