Re: [NFS] RE: [autofs] multiple servers per automount

[Tim Hockin <thockin@hockin.org>]

On Thu, Oct 23, 2003 at 01:00:57PM -0400, Mike Waychison wrote:
> >Would a GFP_ATOMIC make a difference to the analysis?
 
> Yes, sleeping within a spinlock is bad practice because it may 
> eventually deadlock.  Pretend that the lock is taken, the call to 
> kmalloc is made, the mm system doesn't have any immidiately free memory 
> and through some flow of execution requires that a some pseudo-block 
> device backed filesystem needs to be mounted -> deadlock.  I have no 
> idea if this is currently a likely scenario, however not sleeping within 
> a lock is 'The Right Thing' and should be avoided at all costs. 

it's worse than that.  It's forbidden.  It's a VERY likely deadlock scenario
in the general sense, even if this particular case is not.  If you need to
lock something and you need to sleep holding that lock, use a semaphore.

-- 
Notice that as computers are becoming easier and easier to use,
suddenly there's a big market for "Dummies" books.  Cause and effect,
or merely an ironic juxtaposition of unrelated facts?