jhb 2007-10-27 22:07:40 UTC
FreeBSD src repository
Modified files:
sys/kern sched_4bsd.c
Log:
Change the roundrobin implementation in the 4BSD scheduler to trigger a
userland preemption directly from hardclock() via sched_clock() when a
thread uses up a full quantum instead of using a periodic timeout to cause
a userland preemption every so often. This fixes a potential deadlock
when IPI_PREEMPTION isn't enabled where softclock blocks on a lock held
by a thread pinned or bound to another CPU. The current thread on that
CPU will never be preempted while softclock is blocked.
Note that ULE already drives its round-robin userland preemption from
sched_clock() as well and always enables IPI_PREEMPT.
MFC after: 1 week
Revision Changes Path
1.108 +8 -29 src/sys/kern/sched_4bsd.c
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