Author: fabient
Date: Fri May 6 14:11:20 2011
New Revision: 221532
URL: http://svn.freebsd.org/changeset/base/221532
Log:
MFC r220198:
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.
Modified:
stable/7/sys/kern/sched_4bsd.c
stable/7/sys/kern/sched_ule.c
Directory Properties:
stable/7/sys/ (props changed)
stable/7/sys/cddl/contrib/opensolaris/ (props changed)
stable/7/sys/contrib/dev/acpica/ (props changed)
stable/7/sys/contrib/pf/ (props changed)
Modified: stable/7/sys/kern/sched_4bsd.c
==============================================================================
--- stable/7/sys/kern/sched_4bsd.c Fri May 6 14:11:01 2011
(r221531)
+++ stable/7/sys/kern/sched_4bsd.c Fri May 6 14:11:20 2011
(r221532)
@@ -848,13 +848,9 @@ sched_switch(struct thread *td, struct t
if ((p->p_flag & P_NOLOAD) == 0)
sched_load_rem();
- if (newtd) {
- MPASS(newtd->td_lock == &sched_lock);
- newtd->td_flags |= (td->td_flags & TDF_NEEDRESCHED);
- }
-
td->td_lastcpu = td->td_oncpu;
- td->td_flags &= ~TDF_NEEDRESCHED;
+ if (!(flags & SW_PREEMPT))
+ td->td_flags &= ~TDF_NEEDRESCHED;
td->td_owepreempt = 0;
td->td_oncpu = NOCPU;
Modified: stable/7/sys/kern/sched_ule.c
==============================================================================
--- stable/7/sys/kern/sched_ule.c Fri May 6 14:11:01 2011
(r221531)
+++ stable/7/sys/kern/sched_ule.c Fri May 6 14:11:20 2011
(r221532)
@@ -1879,7 +1879,8 @@ sched_switch(struct thread *td, struct t
#endif
td->td_lastcpu = td->td_oncpu;
td->td_oncpu = NOCPU;
- td->td_flags &= ~TDF_NEEDRESCHED;
+ if (!(flags & SW_PREEMPT))
+ td->td_flags &= ~TDF_NEEDRESCHED;
td->td_owepreempt = 0;
/*
* The lock pointer in an idle thread should never change. Reset it
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