2010/8/11 John Baldwin <j...@freebsd.org>: > Attilio Rao wrote: >> >> 2010/8/11 John Baldwin <j...@freebsd.org>: >>> >>> Attilio Rao wrote: >>>> >>>> Author: attilio >>>> Date: Wed Aug 11 10:51:27 2010 >>>> New Revision: 211176 >>>> URL: http://svn.freebsd.org/changeset/base/211176 >>>> >>>> Log: >>>> IPI handlers may run generally with interrupts disabled because they >>>> are served via an interrupt gate. >>>> However, that doesn't explicitly prevent preemption and thread >>>> migration thus scheduler pinning may be necessary in some handlers. >>>> Fix that. >>>> Tested by: gianni >>>> MFC after: 1 month >>> >>> Actually that does prevent preemption if you do not call any code that >>> would >>> schedule a thread. I think this change is all safe to revert. >> >> Do you recall, then, why lapic_handle_timer() does critical section? >> It seems to be catered by interrupt gate as well, and I don't see any >> point re-enabling them explicitly. > > Because hardclock() explicitly calls sched_add() via swi_sched() when > scheduling the softclock swi. The critical section there is just to ensure > that the preemption to softclock happens after all of the clock interrupt > handlers have finished. However, PCPU_GET() does not call sched_add(), so > it does not need to be protected.
Oh, sorry, was looking at the -CURRENT code which had no explicit call to hardclock (it uses the new timer infrastructure, so that was not so obvious). I understand now, so I will rever the change asap. Thanks, Attilio -- Peace can only be achieved by understanding - A. Einstein _______________________________________________ svn-src-head@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/svn-src-head To unsubscribe, send any mail to "svn-src-head-unsubscr...@freebsd.org"
