[Gc] some more info on previously mentioned hangups

Travis Griggs tgriggs at key.net
Wed Aug 31 10:17:34 PDT 2005

A week or so ago, I was asking some questions, based on the fact that 
we were seeing thread lockups. We run a number of different levels of 
real time (and some not real time too) thread priorities.

We think we've found a part of the problem: vsyslog(). We use this a 
bunch in our system. We current have a system we can deadlock in a 
matter of minutes. If we comment out (i.e. noop) the syslog calls, then 
everything works great. Why am I posting this on the libgc list?

One thing that the sparse documentation about vsyslog alludes to is 
that it is not signal safe. We don't actually have any signal handling 
code in our system, but we've looked at the libgc source... and we know 
it does :) We've tried with both the debian libgc (6.4 I think?) and a 
stock build of the 7 of alpha 4 (which I assume still uses signals to 
do the stop_world (will go check in a second)) and both exhibit the 

I'm wondering if others more familiar either signals, async unsafe 
code, the libgc stop mechanism, might see a potential deadlock 
situation here.


Travis Griggs
"It had better be a pretty good meeting, to be better than no meeting
at all" -- Boyd K Packer

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