On 12/20/21 1:34 PM, Wander Costa wrote:
> On Mon, Dec 20, 2021 at 5:24 PM Jens Axboe <axboe@xxxxxxxxx> wrote:
>>
>> On 12/20/21 12:49 PM, Wander Costa wrote:
>>> On Mon, Dec 20, 2021 at 4:38 PM Jens Axboe <axboe@xxxxxxxxx> wrote:
>>>>
>>>> On 12/20/21 12:28 PM, Wander Lairson Costa wrote:
>>>>> The running_trace_lock protects running_trace_list and is acquired
>>>>> within the tracepoint which implies disabled preemption. The spinlock_t
>>>>> typed lock can not be acquired with disabled preemption on PREEMPT_RT
>>>>> because it becomes a sleeping lock.
>>>>> The runtime of the tracepoint depends on the number of entries in
>>>>> running_trace_list and has no limit. The blk-tracer is considered debug
>>>>> code and higher latencies here are okay.
>>>>
>>>> You didn't put a changelog in here. Was this one actually compiled? Was
>>>> it runtime tested?
>>>
>>> It feels like the changelog reached the inboxes after patch (at least
>>> mine was so). Would you like that I send a v6 in the hope things
>>> arrive in order?
>>
>> Not sure how you are sending them, but they don't appear to thread
>> properly. But the changelog in the cover letter isn't really a
>> changelog, it doesn't say what changed.
>>
>
> Sorry, I think I was too brief in my explanation. I am backporting
> this patch to the RHEL 9 kernel (which runs kernel 5.14). I mistakenly
> generated the v4 patch from that tree, but it lacks this piece
>
> @@ -1608,9 +1608,9 @@ static int blk_trace_remove_queue(struct request_queue *q)
>
> if (bt->trace_state == Blktrace_running) {
> bt->trace_state = Blktrace_stopped;
> - spin_lock_irq(&running_trace_lock);
> + raw_spin_lock_irq(&running_trace_lock);
> list_del_init(&bt->running_list);
> - spin_unlock_irq(&running_trace_lock);
> + raw_spin_unlock_irq(&running_trace_lock);
> relay_flush(bt->rchan);
> }
>
> Causing the build error. v5 adds that. Sorry again for the confusion.
Right, that's why I asked if a) you had even built this patch, and b) if
you had tested it as well.
--
Jens Axboe
