Date: Thu, 31 Mar 2011 13:59:47 +0000 (UTC) From: Fabien Thomas <fabient@FreeBSD.org> To: cvs-src-old@freebsd.org Subject: cvs commit: src/sys/kern sched_4bsd.c sched_ule.c Message-ID: <201103311400.p2VE05dn082537@repoman.freebsd.org>
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fabient 2011-03-31 13:59:47 UTC
FreeBSD src repository
Modified files:
sys/kern sched_4bsd.c sched_ule.c
Log:
SVN rev 220198 on 2011-03-31 13:59:47Z by fabient
Clearing the flag when preempting will let the preempted thread run
too much time. This can finish in a scheduler deadlock with ping-pong
between two threads.
One sample of this is:
- device lapic (to have a preemption point on critical_exit())
- options DEVICE_POLLING with HZ>1499 (to have lapic freq = hardclock freq)
- running a cpu intensive task (that does not enter the kernel)
- only one CPU on SMP or no SMP.
As requested by jhb@ 4BSD have received the same type of fix instead of
propagating the flag to the new thread.
Reviewed by: jhb, jeff
MFC after: 1 month
Revision Changes Path
1.150 +2 -6 src/sys/kern/sched_4bsd.c
1.291 +2 -1 src/sys/kern/sched_ule.c
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