Commit:     bdecea3a9282d529b54954f3f1e59877629baba1
Parent:     2bd7e20e0d24325b0799544bc8105cc57cc8e2aa
Author:     Siddha, Suresh B <[EMAIL PROTECTED]>
AuthorDate: Tue May 8 00:32:48 2007 -0700
Committer:  Linus Torvalds <[EMAIL PROTECTED]>
CommitDate: Tue May 8 11:15:17 2007 -0700

    sched: fix idle load balancing in softirqd context
    Periodic load balancing in recent kernels happen in the softirq.  In
    certain -rt configurations, these softirqs are handled in softirqd context.
     And hence the check for idle processor was always returning busy (as
    nr_running > 1).
    This patch captures the idle information at the tick and passes this info
    to softirq context through an element 'idle_at_tick' in rq.
    [EMAIL PROTECTED]: Fix reverse idle at tick logic]
    Signed-off-by: Suresh Siddha <[EMAIL PROTECTED]>
    Acked-by: Ingo Molnar <[EMAIL PROTECTED]>
    Cc: Thomas Gleixner <[EMAIL PROTECTED]>
    Cc: Nick Piggin <[EMAIL PROTECTED]>
    Signed-off-by: Andrew Morton <[EMAIL PROTECTED]>
    Signed-off-by: Linus Torvalds <[EMAIL PROTECTED]>
 kernel/sched.c |   12 +++++-------
 1 files changed, 5 insertions(+), 7 deletions(-)

diff --git a/kernel/sched.c b/kernel/sched.c
index 5530ed2..ba053d8 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -223,6 +223,7 @@ struct rq {
        unsigned long raw_weighted_load;
 #ifdef CONFIG_SMP
        unsigned long cpu_load[3];
+       unsigned char idle_at_tick;
        unsigned long long nr_switches;
@@ -2943,12 +2944,7 @@ static void run_rebalance_domains(struct softirq_action 
        struct rq *this_rq = cpu_rq(this_cpu);
        unsigned long interval;
        struct sched_domain *sd;
-       /*
-        * We are idle if there are no processes running. This
-        * is valid even if we are the idle process (SMT).
-        */
-       enum idle_type idle = !this_rq->nr_running ?
-                               SCHED_IDLE : NOT_IDLE;
+       enum idle_type idle = this_rq->idle_at_tick ? SCHED_IDLE : NOT_IDLE;
        /* Earliest time when we have to call run_rebalance_domains again */
        unsigned long next_balance = jiffies + 60*HZ;
@@ -3218,14 +3214,16 @@ void scheduler_tick(void)
        unsigned long long now = sched_clock();
        struct task_struct *p = current;
        int cpu = smp_processor_id();
+       int idle_at_tick = idle_cpu(cpu);
        struct rq *rq = cpu_rq(cpu);
        update_cpu_clock(p, rq, now);
-       if (p != rq->idle)
+       if (!idle_at_tick)
                task_running_tick(rq, p);
 #ifdef CONFIG_SMP
+       rq->idle_at_tick = idle_at_tick;
        if (time_after_eq(jiffies, rq->next_balance))
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