svn commit: r192535 - head/sys/kern

[John Baldwin]

On Thursday 21 May 2009 9:29:57 am Attilio Rao wrote:
> 2009/5/21 Kostik Belousov <kostikbel at gmail.com>:
> > On Thu, May 21, 2009 at 01:22:07PM +0000, Attilio Rao wrote:
> >> Author: attilio
> >> Date: Thu May 21 13:22:07 2009
> >> New Revision: 192535
> >> URL: http://svn.freebsd.org/changeset/base/192535
> >>
> >> Log:
> >>   Move the M_WAITOK flag in notify() into an M_NOWAIT one in order to 
match
> >>   the behaviour alredy present with the further malloc() call in
> >>   devctl_notify().
> >>   This fixes a bug in the CAM layer where the camisr handler finished to
> >>   call camperiphfree() (and subsequently destroy_dev() resulting in a new
> >>   dev notify) while the xpt lock is held.
> > This is wrong. You cannot call destroy_dev() while holding any mutex.
> > Taking this into account, it makes no sense to use M_NOWAIT in notify().
> 
> As long as devctl_notify() also calls M_NOWAIT and if not available
> skips "silently" it just does the same thing, I think this approach is
> more consistent.
> 
> It remains, though, the fact to fix CAM when calling destroy_dev().
> Maybe we should add a witness_warn() there?

I agree with kib, this should be reverted and CAM fixed instead.  I also agree 
that M_NOWAIT use should be limited where possible.

-- 
John Baldwin