svn commit: r192535 - head/sys/kern
jhb at freebsd.org
Fri May 22 15:26:08 UTC 2009
On Friday 22 May 2009 9:44:18 am Scott Long wrote:
> John Baldwin wrote:
> > On Thursday 21 May 2009 6:11:02 pm Attilio Rao wrote:
> >> At this point I wonder what's the purpose of maintaining the sleeping
> >> version for such functions?
> > Actually, I still very much do not like using M_NOWAIT needlessly. I would
> > much rather the solution for make_dev() be that the 1 or 2 places that need
> > to do it with a mutex held instead queue a task to do the actual make_dev()
> > in a taskqueue when no locks are held. This is basically what
> > destroy_dev_sched() is doing. Perhaps a make_dev_sched() with a similar
> > callback to be called on completion would be better. Having a device driver
> > do all the work to setup the hardware only to fail to create a node in /dev
> > so that userland can actually use it is pretty rediculous and useless.
> It's a lot easier for me to handle a failure of make_dev in CAM than it
> is to decouple the call to it. Please don't dictate policy.
But what is there for CAM to handle? I would expect CAM to handle hardware
events such as the devices arriving or leaving. A temporary memory shortage
it not a hardware event. As a user, if I insert a USB stick when the system
happens to be temporarily low on memory, is it more useful for the cdev to
appear a few microseconds later from a deferred context once memory is
available or for no device to ever appear at all?
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