Re: Notifier chains are unsafe

[Keith Owens]

On Thu, 27 Oct 2005 16:02:08 -0700, 
Chandra Seetharaman <sekharan@xxxxxxxxxx> wrote:
>On Thu, 2005-10-27 at 17:21 -0400, Alan Stern wrote:
>> The other problem is that you violated Keith's statement that 
>> notifier_call_chain shouldn't take any locks.  On the other hand, if we
>
>I would interpret Keith's comment like this: callout should not be
>called with any locks held (because that would limit the callouts from
>blocking). 

We should be able to call notifier_call_chain() from any context.  That
includes oops, panic, NMI and other unmaskable machine check events.
If you can call notifier_call_chain() from an unmaskable context then
it follows that the callbacks cannot take any locks.  Locks are not
safe in NMI context.

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