Re: Regression: commit 045065d breaks kernel on machine with atapi floppy: high IOWAIT, hung processes (patch exists)

[Sergio Callegari <sergio.callegari@unibo.it>]

Patch in https://lkml.org/lkml/2014/11/20/25 fixes the issue for me.

Furthermore, to the best of my understanding it fixes the issue not just 
for me but for many others too.

Can it please be applied both to the current kernel and to the stable 
kernels?

Best regards,

Sergio


On 16/08/2015 17:01, Sergio Callegari wrote:
> Seems that the issue also affects other systems with different configs:
>
> https://bbs.archlinux.org/viewtopic.php?id=189324
>
> Possibly, the same bug reported in
>
> https://bugzilla.kernel.org/show_bug.cgi?id=87581
>
> A tentative patch was submitted on LKML
>
> https://lkml.org/lkml/2014/11/20/581
>
> I have not tested it yet.
>
> Another possible solution being reported is increasing delay time in 
> blk_delay_queue(q, SCSI_QUEUE_DELAY)
>
> Not tested yet either.
>
> Threads in 189324 suggests that bug is triggered by mixing a slower 
> device with a faster one on the same IDE/SATA channel.
>
> Can someone indicate:
>
> - If one of the two patches has already been accepted in recent 
> kernels or is pending acceptance?
>
> - Which one among the two approaches (extending delay time or 
> modifying spin locks in scsi_lib.c) is more appropriate for me to test?
>
> Best,
>
> Sergio
>
>
>
> On 16/08/2015 16:19, Sergio Callegari wrote:
>>
>> Hi,
>>
>> please keep me in CC in answers.
>>
>> I'd like to report that after commit
>>
>> [045065d8a300a37218c548e9aa7becd581c6a0e8] [SCSI] fix qemu boot hang
>> problem
>>
>> the kernel is not usable on a machine with an IOMEGA Zip 100 ATAPI drive
>> as in:
>>
>> Model=IOMEGA ZIP 100 ATAPI Floppy, FwRev=12.A, SerialNo=
>> Config={ SpinMotCtl Removeable nonMagnetic }
>> RawCHS=0/0/0, TrkSize=0, SectSize=0, ECCbytes=0
>> BuffType=unknown, BuffSize=unknown, MaxMultSect=0 (maybe): CurCHS=0/0/0,
>> CurSects=0, LBA=yes, LBAsects=0
>> IORDY=on/off, tPIO={min:500,w/IORDY:180}
>> PIO modes: pio0 pio1 pio2 pio3
>> AdvancedPM=no
>>
>> Symptoms include:
>>
>> - Extremely high IOWAIT in absence of load
>> - Kernel reporting hung processes
>> - Commands like blkid hanging
>> - Inability of the machine to shutdown
>>
>> Symptoms do not appear immediately, but after some time (anywhere
>> between a few minutes and /many hours/ after boot). First symptom is
>> IOWAIT suddendly jumping high.
>>
>> Due to the delay in which symptoms manifest, bisecting has been quite
>> painful, but I am now rather sure that the first bad commit is the one
>> above.
>>
>> Other pieces of hardware configuration include:
>>
>> - ASRock N68S motherboard with AMD Phenom(tm) II X4 920 Processor and
>> NVIDIA MCP61 SATA/IDE Chipset
>> - IDE drive connected as slave on ide interface where master is HL-DT-ST
>> DVD-RAM GH22NP20 CDROM/DVD writer
>>
>> Issue is weird because the commit seems to merely fix a trivial error in
>> logic condition
>>
>> -       if (atomic_read(&sdev->device_busy) && 
>> !scsi_device_blocked(sdev))
>> +       if (!atomic_read(&sdev->device_busy) && 
>> !scsi_device_blocked(sdev))
>>                  blk_delay_queue(q, SCSI_QUEUE_DELAY);
>>
>> Hence, the commit may just end up making visible some other issue.
>>
>> Best,
>>
>> Sergio
>>
>>
>