max workqueue name length

max workqueue name length

[Frederic TEMPORELLI]

Hello,


When creating a workqueue, workqueue name is limited to 10 chars
(kernel/workqueue.c , function is __create_workqueue, test is done in a BUG_ON).

Why has this length be limited to 10 chars ?
Can I safely increase this max length (13 chars should be enough...) ?



Some comments about these questions:

In SCSI layer, HBA kernel ID is incremented after each modprobe/rmmod.

Then, when a scsi driver is managing a working queue and HBA kernel ID is 
greater than 99 (let's assume that you have modprobe/rmmod the scsi driver to 
get this ID to 99, or you may have play with 'scsi_debug' module), an oops is 
generated when loading again the driver (and the driver is frozen).

This is because working queue name format is "scsi_wq_%d" (drivers/scsi/hosts.c 
, function scsi_add_host, %d is the HBA ID), and so working queue name length is 
greater than 10 chars when HBA kernel ID is > 99...


Best regards


-- 
Frederic TEMPORELLI

Re: kernel workqueue -max name length

[Frederic TEMPORELLI]

Hi,


any explanation about the 10 chars limit for kernel workqueue name ?


another question: why is the name length test managed by BUG_ON ?
returning a NULL workqueue is done in the next test (failed kmalloc for wq)...

Anyway, this can explain some issues when loading some SCSI drivers modules.


hope that somebody knows...


Frederic TEMPORELLI wrote:
> Hello,
> 
> 
> When creating a workqueue, workqueue name is limited to 10 chars
> (kernel/workqueue.c , function is __create_workqueue, test is done in a 
> BUG_ON).
> 
> Why has this length be limited to 10 chars ?
> Can I safely increase this max length (13 chars should be enough...) ?
> 
> 
> 
> Some comments about these questions:
> 
> In SCSI layer, HBA kernel ID is incremented after each modprobe/rmmod.
> 
> Then, when a scsi driver is managing a working queue and HBA kernel ID 
> is greater than 99 (let's assume that you have modprobe/rmmod the scsi 
> driver to get this ID to 99, or you may have play with 'scsi_debug' 
> module), an oops is generated when loading again the driver (and the 
> driver is frozen).
> 
> This is because working queue name format is "scsi_wq_%d" 
> (drivers/scsi/hosts.c , function scsi_add_host, %d is the HBA ID), and 
> so working queue name length is greater than 10 chars when HBA kernel ID 
> is > 99...
> 
> 
> Best regards
> 
> 


-- 
Frederic TEMPORELLI