Hello everyone, > Also, SCSI_QUEUE_DELAY seems like an arbitrary magic number; > maybe that value isn't working correctly anymore? this is an excellent remark from Robert Elliot, this gives me an idea : try to set manually a value in the if() statement ( line 1779 in file /drivers/scsi/scsi_lib.c ) by default the value of SCSI_QUEUE_DELAY is 3 ms, which might be inapropriate with some slow harddisks and with the changes made by the commit 74665016086615bbaa3fa6f83af410a0a4e029ee ( scsi: convert host_busy to atomic_t ), after further tests I discover that the value 40 ms solves my problem, the bug is gone with this value, here is the patch who sets 40 ms in the if() statement : --- a/drivers/scsi/scsi_lib.c 2014-10-05 21:23:04.000000000 +0200 +++ b/drivers/scsi/scsi_lib.c 2014-11-16 17:39:16.819674725 +0100 @@ -1776,7 +1776,7 @@ static void scsi_request_fn(struct reque atomic_dec(&sdev->device_busy); out_delay: if (!atomic_read(&sdev->device_busy) && !scsi_device_blocked(sdev)) - blk_delay_queue(q, SCSI_QUEUE_DELAY); + blk_delay_queue(q, 40); } static inline int prep_to_mq(int ret) with this patch the value of SCSI_QUEUE_DELAY is still 3 ms, but here we use 40 ms only in a specific part of scsi_lib.c file ( line 1779, it's this part where the bug seems to be triggered, so that's why I set 40 ms here in the blk_delay_queue() function ) after applying this patch I don't see problems related to I/O performance/speed, all is ok, the question is now : why putting a higher value in line 1779 does solve the bug ? and why before the commit 74665016086615bbaa3fa6f83af410a0a4e029ee I don't have problems even with a value of 3 ms for SCSI_QUEUE_DELAY ? Le 14/11/2014 08:32, Christoph Hellwig a écrit : > On Thu, Nov 13, 2014 at 11:55:38PM +0100, Barto wrote: >> it's interesting, with this commit >> 74665016086615bbaa3fa6f83af410a0a4e029ee I have the bug : >> >> scsi: convert host_busy to atomic_t : > > At this point we'll need a bisction between v3.16 as the last good > point, and 74665016086615bbaa3fa6f83af410a0a4e029ee as the known bad > point. > -- To unsubscribe from this list: send the line "unsubscribe linux-scsi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
