cvs commit: src/sys/kern kern_event.c src/sys/sys eventvar.h
nate at root.org
Wed Jul 14 12:06:40 PDT 2004
Doug Rabson wrote:
> On Wednesday 14 July 2004 19:56, Robert Watson wrote:
>>On Wed, 14 Jul 2004, Alfred Perlstein wrote:
>>>I can fix this by setting a "sigio in progress" on the kqeue and
>>>not calling pgsigio() while one is in progress.
>>My worry is the inter-subsystem calling. We often call KNOTE() while
>>holding existing locks in the calling subsystem that we can't drop.
>>Generally, kqueue is a leaf node subsystem in that it's called from
>>many places under many circumstances, and needs to not disrupt the
>>calling state by doing "weird things". What's there before your
>>change is not too disruptive/weird; afterwards, we call into the body
>>of the process signalling code which requires additional process
>>locks. Note that there are other paths to the same suffering: if any
>>other signal is delivered to a process that's monitoring for signals
>>with kqueue causing a sigio, you're still recursing into the signal
> Seems to me that the best thing to do is to defer the psigio() to a
> taskqueue that will run in a simpler locking environment.
In fact, the AIO task threads already provide a convenient context for this.
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