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Fix a bug with sched_affinity() where it checks td_pinned of another

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thread in a racy manner, which can lead to attempting to migrate a
thread that is pinned to a CPU.  Instead, have sched_switch() determine
which CPU a thread should run on if the current one is not allowed.

KASSERT in sched_bind() that the thread is not yet pinned to a CPU.

KASSERT in sched_switch() that only migratable threads or those moving
due to a sched_bind() are changing CPUs.

sched_affinity code came from jhb@.

MFC after:	2 weeks
This commit is contained in:
Matthew D Fleming 2010-09-01 20:32:47 +00:00
parent 91c265b83d
commit 0f7a0ebd59
1 changed files with 13 additions and 11 deletions
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24
sys/kern/sched_ule.c
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@ -1797,10 +1797,16 @@ sched_switch(struct thread *td, struct thread *newtd, int flags)
srqflag = (flags & SW_PREEMPT) ?
SRQ_OURSELF|SRQ_YIELDING|SRQ_PREEMPTED :
SRQ_OURSELF|SRQ_YIELDING;
if (THREAD_CAN_MIGRATE(td) && !THREAD_CAN_SCHED(td, ts->ts_cpu))
ts->ts_cpu = sched_pickcpu(td, 0);
if (ts->ts_cpu == cpuid)
tdq_runq_add(tdq, td, srqflag);
else
else {
KASSERT(THREAD_CAN_MIGRATE(td) ||
(ts->ts_flags & TSF_BOUND) != 0,
("Thread %p shouldn't migrate", td));
mtx = sched_switch_migrate(tdq, td, srqflag);
}
} else {
/* This thread must be going to sleep. */
TDQ_LOCK(tdq);
@ -2383,7 +2389,6 @@ sched_affinity(struct thread *td)
{
#ifdef SMP
struct td_sched *ts;
int cpu;
THREAD_LOCK_ASSERT(td, MA_OWNED);
ts = td->td_sched;
@ -2397,17 +2402,13 @@ sched_affinity(struct thread *td)
if (!TD_IS_RUNNING(td))
return;
td->td_flags |= TDF_NEEDRESCHED;
if (!THREAD_CAN_MIGRATE(td))
return;
/*
* Assign the new cpu and force a switch before returning to
* userspace. If the target thread is not running locally send
* an ipi to force the issue.
* Force a switch before returning to userspace. If the
* target thread is not running locally send an ipi to force
* the issue.
*/
cpu = ts->ts_cpu;
ts->ts_cpu = sched_pickcpu(td, 0);
if (cpu != PCPU_GET(cpuid))
ipi_cpu(cpu, IPI_PREEMPT);
if (td != curthread)
ipi_cpu(ts->ts_cpu, IPI_PREEMPT);
#endif
}
@ -2424,6 +2425,7 @@ sched_bind(struct thread *td, int cpu)
ts = td->td_sched;
if (ts->ts_flags & TSF_BOUND)
sched_unbind(td);
KASSERT(THREAD_CAN_MIGRATE(td), ("%p must be migratable", td));
ts->ts_flags |= TSF_BOUND;
sched_pin();
if (PCPU_GET(cpuid) == cpu)