Re: Question for Patch"libsas: fix "sysfs group not found" warnings at port teardown time"

2016-02-08 Thread John Garry 

On 05/02/2016 21:33, Praveen Murali wrote:

Hi Yijing,
   The fix was deemed inappropriate and I think the explanation provided by 
James was kind similar to what your observation is. Also, as far as I remember 
the consensus was that these error messages (sysfs group not found) are 
harmless at this point. I think James can provide a better explanation and 
direction for you (copying him here).

Praveen



I can't find the original full discussion on this. My impression is that 
the fix is incorrect as the port should not be deleted in 
sas_destruct_devices(). I also tried this patch and got a NULL deference 
when I unplugged the disk from the expander.


We get the warn as the port is deleted before the device which is 
attached to it. The tricky part is that the port and devices are deleted 
in seperate work structs being processed in same work queue (shost wq). 
The first cannot be relinquished to allow the second to run.


One (undesirable) solution is to call sas_destruct_devices() directly 
from sas_unregister_dev().



On Feb 5, 2016, at 1:20 AM, wangyijing  wrote:

Hi Dan and Praveen,
   I found a patch titled "libsas: fix "sysfs group not found" warnings at port 
teardown time" by google,
https://www.mail-archive.com/linux-scsi@vger.kernel.org/msg39187.html

I found the same warning calltrace in my platform, but I didn't find the patch 
changes in the latest kernel 4.5-rc2.
So is this issue still in kernel ?

I think your patch could fix this issue we found, but I'm worried about another 
problem.

Now when unplug a disk

LLDD report a event loss_of_singal
sas_deform_port
sas_unregister_domain_devices
sas_unregister_dev
sas_discover_event(dev->port, DISCE_DESTRUCT);
sas_port_delete
phy->port = NULL;

and after your patch changes

LLDD report a event loss_of_singal
sas_deform_port
sas_unregister_domain_devices
sas_unregister_dev
sas_discover_event(dev->port, DISCE_DESTRUCT);
phy->port = NULL;

...
sas_destruct_devices
sas_port_delete   //now we actually delete the port device, but we 
set  phy->port = NULL;  before this time.


So if we hotplug the disk quickly, plug,unplug,plug,
The new dmaed event(plug) would try to alloc and add a new port, but the old 
port device is still alive.
Another calltrace would occur

WARNING: CPU: 0 PID: 1038 at lib/kobject.c:240 
kobject_add_internal+0x258/0x318()
kobject_add_internal failed for port-0:0 with -EEXIST, don't try to register 
things with the same name in the same directory.
CPU: 0 PID: 1038 Comm: kworker/u64:2 Tainted: GW   4.1.6+ #140
[] dump_backtrace+0x0/0x124
[] show_stack+0x10/0x1c
[] warn_slowpath_fmt+0x4c/0x58
[] device_add+0x28c/0x5b8
[] sas_port_add+0x20/0xbc
[] sas_porte_bytes_dmaed
[] process_one_work+0x13c/0x344

Because I am not a sas guy, so if you could comment this or post new patch, I 
would be thanks a lot!

Thanks!
Yijing.



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Re: Question for Patch"libsas: fix "sysfs group not found" warnings at port teardown time"

2016-02-05 Thread Praveen Murali 
Hi Yijing,
  The fix was deemed inappropriate and I think the explanation provided by 
James was kind similar to what your observation is. Also, as far as I remember 
the consensus was that these error messages (sysfs group not found) are 
harmless at this point. I think James can provide a better explanation and 
direction for you (copying him here).

Praveen

> On Feb 5, 2016, at 1:20 AM, wangyijing  wrote:
> 
> Hi Dan and Praveen,
>   I found a patch titled "libsas: fix "sysfs group not found" warnings at 
> port teardown time" by google,
> https://www.mail-archive.com/linux-scsi@vger.kernel.org/msg39187.html
> 
> I found the same warning calltrace in my platform, but I didn't find the 
> patch changes in the latest kernel 4.5-rc2.
> So is this issue still in kernel ?
> 
> I think your patch could fix this issue we found, but I'm worried about 
> another problem.
> 
> Now when unplug a disk
> 
> LLDD report a event loss_of_singal
>sas_deform_port
>   sas_unregister_domain_devices
>   sas_unregister_dev
>   sas_discover_event(dev->port, DISCE_DESTRUCT);
>   sas_port_delete
>   phy->port = NULL;
> 
> and after your patch changes
> 
> LLDD report a event loss_of_singal
>   sas_deform_port
>   sas_unregister_domain_devices
>   sas_unregister_dev
>   sas_discover_event(dev->port, DISCE_DESTRUCT);
>   phy->port = NULL;
> 
> ...
>   sas_destruct_devices
>   sas_port_delete   //now we actually delete the port device, but 
> we set  phy->port = NULL;  before this time.
> 
> 
> So if we hotplug the disk quickly, plug,unplug,plug,
> The new dmaed event(plug) would try to alloc and add a new port, but the old 
> port device is still alive.
> Another calltrace would occur
> 
> WARNING: CPU: 0 PID: 1038 at lib/kobject.c:240 
> kobject_add_internal+0x258/0x318()
> kobject_add_internal failed for port-0:0 with -EEXIST, don't try to register 
> things with the same name in the same directory.
> CPU: 0 PID: 1038 Comm: kworker/u64:2 Tainted: GW   4.1.6+ #140
> [] dump_backtrace+0x0/0x124
> [] show_stack+0x10/0x1c
> [] warn_slowpath_fmt+0x4c/0x58
> [] device_add+0x28c/0x5b8
> [] sas_port_add+0x20/0xbc
> [] sas_porte_bytes_dmaed
> [] process_one_work+0x13c/0x344
> 
> Because I am not a sas guy, so if you could comment this or post new patch, I 
> would be thanks a lot!
> 
> Thanks!
> Yijing.
> 
> 
> 
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> the body of a message to majord...@vger.kernel.org
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Re: Question for Patch"libsas: fix "sysfs group not found" warnings at port teardown time"

2016-02-05 Thread Dāvis Mosāns 
2016-02-05 11:20 GMT+02:00 wangyijing :
>
> Hi Dan and Praveen,
>I found a patch titled "libsas: fix "sysfs group not found" warnings at
> port teardown time" by google,
> https://www.mail-archive.com/linux-scsi@vger.kernel.org/msg39187.html
>

 Maybe this is related?

 kernel: WARNING: CPU: 4 PID: 16820 at fs/sysfs/group.c:237
 sysfs_remove_group+0x8b/0x90()
 kernel: sysfs group 818a3b60 not found for kobject 'end_device-7:7'
 [...]
 kernel: Workqueue: scsi_wq_7 sas_destruct_devices [libsas]

 I'm getting this warning when removing disk from HighPoint RocketRAID 2760
 controller (mvsas driver)
 See https://bugzilla.kernel.org/show_bug.cgi?id=71021#c3
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Re: Question for Patch"libsas: fix "sysfs group not found" warnings at port teardown time"

2016-02-05 Thread wangyijing 
Yes, it seems to be the same issue.

在 2016/2/6 1:22, Dāvis Mosāns 写道:
> 2016-02-05 11:20 GMT+02:00 wangyijing :
>>
>> Hi Dan and Praveen,
>>I found a patch titled "libsas: fix "sysfs group not found" warnings at
>> port teardown time" by google,
>> https://www.mail-archive.com/linux-scsi@vger.kernel.org/msg39187.html
>>
> 
>  Maybe this is related?
> 
>  kernel: WARNING: CPU: 4 PID: 16820 at fs/sysfs/group.c:237
>  sysfs_remove_group+0x8b/0x90()
>  kernel: sysfs group 818a3b60 not found for kobject 'end_device-7:7'
>  [...]
>  kernel: Workqueue: scsi_wq_7 sas_destruct_devices [libsas]
> 
>  I'm getting this warning when removing disk from HighPoint RocketRAID 2760
>  controller (mvsas driver)
>  See https://bugzilla.kernel.org/show_bug.cgi?id=71021#c3
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> 
> 

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