On Sunday 28 June 2009 11:57:05 am Robert Watson wrote: > > On Sun, 28 Jun 2009, Sebastian Huber wrote: > > > suppose that a certain time event triggered several callout functions. What > > happens if the first of these callout functions blocks on the Giant lock? > > Does this delay all further callout functions until the Giant lock is > > available for the first callout function? What happens if one of the > > callout > > function blocks forever? Does this deadlock the system? > > 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. -- John Baldwin _______________________________________________ [email protected] mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-hackers To unsubscribe, send any mail to "[email protected]"
