Re: 2.6.0-test9 and sleeping function called from invalid context

[viro]

On Sat, Oct 25, 2003 at 10:49:50PM -0700, Andrew Morton wrote:
> Andrew Morton <akpm@xxxxxxxx> wrote:
> >
> > but the wider question would be: is the SELinux
> >  d_instantiate callout allowed to sleep?  A quick audit seems to indicate
> >  that it's OK, but only by luck I think.
> 
> proc_pid_lookup() calls d_add->d_instantiate under task->proc_lock, so
> inode_doinit_with_dentry() is called under spinlock on this path as well.
> 
> Manfred, is there any particular reason why proc_pid_lookup()'s d_add is
> inside the lock?

AFAICS, we can move d_add() right before taking the spinlock.  It's there
to protect the ->proc_dentry assignment.

*However*, I would like to point out that we are holding ->i_sem on the
procfs root at that point, so any blocking code in d_instantiate() would
better be careful to avoid deadlocks if it wants to play with procfs itself -
we are not in a locking-neutral situation here, spinlock or not.
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