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author | Ingo Molnar <mingo@elte.hu> | 2009-05-07 11:18:34 +0200 |
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committer | Ingo Molnar <mingo@elte.hu> | 2009-05-07 13:36:22 +0200 |
commit | 0ad5d703c6c0fcd385d956555460df95dff7eb7e (patch) | |
tree | 4b777100f9be4fe90ca4bd043b9f98df672b5b3b /kernel/sched.c | |
parent | 44347d947f628060b92449702071bfe1d31dfb75 (diff) | |
parent | 1cb81b143fa8f0e4629f10690862e2e52ca792ff (diff) | |
download | op-kernel-dev-0ad5d703c6c0fcd385d956555460df95dff7eb7e.zip op-kernel-dev-0ad5d703c6c0fcd385d956555460df95dff7eb7e.tar.gz |
Merge branch 'tracing/hw-branch-tracing' into tracing/core
Merge reason: this topic is ready for upstream now. It passed
Oleg's review and Andrew had no further mm/*
objections/observations either.
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Diffstat (limited to 'kernel/sched.c')
-rw-r--r-- | kernel/sched.c | 43 |
1 files changed, 43 insertions, 0 deletions
diff --git a/kernel/sched.c b/kernel/sched.c index 14a19b1..6530a27 100644 --- a/kernel/sched.c +++ b/kernel/sched.c @@ -2011,6 +2011,49 @@ migrate_task(struct task_struct *p, int dest_cpu, struct migration_req *req) } /* + * wait_task_context_switch - wait for a thread to complete at least one + * context switch. + * + * @p must not be current. + */ +void wait_task_context_switch(struct task_struct *p) +{ + unsigned long nvcsw, nivcsw, flags; + int running; + struct rq *rq; + + nvcsw = p->nvcsw; + nivcsw = p->nivcsw; + for (;;) { + /* + * The runqueue is assigned before the actual context + * switch. We need to take the runqueue lock. + * + * We could check initially without the lock but it is + * very likely that we need to take the lock in every + * iteration. + */ + rq = task_rq_lock(p, &flags); + running = task_running(rq, p); + task_rq_unlock(rq, &flags); + + if (likely(!running)) + break; + /* + * The switch count is incremented before the actual + * context switch. We thus wait for two switches to be + * sure at least one completed. + */ + if ((p->nvcsw - nvcsw) > 1) + break; + if ((p->nivcsw - nivcsw) > 1) + break; + + cpu_relax(); + } +} + +/* * wait_task_inactive - wait for a thread to unschedule. * * If @match_state is nonzero, it's the @p->state value just checked and |