Re: [PATCH] remove name length check in a workqueue

[James Bottomley]

On Wed, 2005-08-10 at 10:37 -0700, Andrew Morton wrote:
> > and anyway, it doesn't have to be unique;
> > set_task_comm just does a strlcpy from the name, so it will be truncated
> > (same as for a binary with > 15 character name).
> 
> Yup.  But it'd be fairly silly to go adding the /%d, only to have it
> truncated off again.

Well, but the other alternative is that we hit arbitrary BUG_ON() limits
in systems that create numbered workqueues which is rather contrary to
our scaleability objectives, isn't it?

I think I'd rather the name truncation than have to respond to kernel
BUG()'s.  If someone really has a problem with the appearance of ps,
they can always increase TASK_COMM_LEN.

> We could truncate the name before adding the CPU number, but it sounds
> saner to just prevent anyone passing in excessively long names.  Via
> BUG_ON, say ;)
> 
> What's the actual problem?

What I posted originally; the current SCSI format for a workqueue:
scsi_wq_%d hits the bug after the host number rises to 100, which has
been seen by some enterprise person with > 100 HBAs.

The reason for this name is that the error handler thread is called
scsi_eh_%d; so we could rename all our threads to avoid this, but one
day someone will come along with a huge enough machine to hit whatever
limit we squeeze it down to.

James


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