On 13 Jul 2009, at 19:17, John Baldwin wrote:
>> Callouts are marked as MPSAFE or non-MPSAFE when registered. If
>> non-MPSAFE,
>> we will acquire Giant automatically for the callout, but I believe
>> we'll also
>> try and sort non-MPSAFE callouts behind MPSAFE ones in execution
>> order to
>> minimize latency for MPSAFE callouts. Most callouts acquire locks
>> of some
>> sort, and stalling any callout indefinitely will stall the entire
>> callout
>> thread indefinitely, which in turn could lead to a variety of odd
>> behaviors
>> and potentially (although not necessarily) deadlock.
>
> FWIW, we do not actually sort the callouts in this manner, so all
> callouts
> will be blocked until Giant is acquired.
I must have been remembering a proposed change -- as you say, it's
certainly not in kern_timeout.c. However, I'd rather just eliminate
support for Giant in callouts in 9.x than try to further facilitate
them :-)
Robert
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