On 09/16/2013 03:23 AM, Jan Kara wrote: > Hi, > > I've been looking into a problem where BLK_TN_PROCESS events are not > delivered to all devices which are being traced. This results in process > name being (null) when trace for a single device is parsed. > > The reason for this problem is that trace_note_tsk() is called only if > tsk->btrace_seq != blktrace_seq and it updates tsk->btrace_seq to > blktrace_seq. Thus after a trace for another device is started > BLK_TN_PROCESS event is sent only on behalf of the first device with which > the task interacts. That isn't necessarily the new device thus traces for > some devices accumulate several BLK_TN_PROCESS events for one task while > other have none. Is this a known problem and is this intended to work > better? > > I was thinking how to fix that for a while and it doesn't seem to be > possible without tracking with each block trace which tasks it has been > notified about. And that is relatively expensive...
It is unfortunately a known issue... I have not come up with a good way to fix it either, while keeping it cheap. So if you think of something, do let me know. -- Jens Axboe -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
