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

From: Tim Hockin (thockin_at_hockin.org)
Date: 10/23/03

  • Next message: Rob: "Re: FEATURE REQUEST: Specific Processor Optimizations on x86 Architecture" 
    Date:	Thu, 23 Oct 2003 10:09:42 -0700
To: Mike Waychison <Michael.Waychison@Sun.COM>

    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?
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  • Next message: Rob: "Re: FEATURE REQUEST: Specific Processor Optimizations on x86 Architecture"

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