Re: 2.6.21-rc2-mm1 - build error with CONFIG_NO_HZ=y and CONFIG_SMP=n

Andrew Morton
2007-03-03T07:59:52Z

On Sat, 03 Mar 2007 15:45:52 +0800 "Antonino A. Daplas" <adaplas@gmail.com> wrote:

> On Fri, 2007-03-02 at 03:00 -0800, Andrew Morton wrote:
>
> I get this with CONFIG_NO_HZ=y, CONFIG_SMP=n
>
> kernel/sched.c: In function ‘trigger_load_balance’:
> kernel/sched.c:3384: error: ‘struct rq’ has no member named
> ‘in_nohz_recently’
> kernel/sched.c:3384: error: ‘struct rq’ has no member named
> ‘idle_at_tick’
> kernel/sched.c:3385: error: ‘struct rq’ has no member named
> ‘in_nohz_recently’
> kernel/sched.c:3387: error: ‘nohz’ undeclared (first use in this
> function)
> kernel/sched.c:3387: error: (Each undeclared identifier is reported only
> once
> kernel/sched.c:3387: error: for each function it appears in.)
> kernel/sched.c:3404: warning: implicit declaration of function
> ‘resched_cpu’
> kernel/sched.c:3412: error: ‘struct rq’ has no member named
> ‘idle_at_tick’
> kernel/sched.c:3422: error: ‘struct rq’ has no member named
> ‘idle_at_tick’
> make[1]: *** [kernel/sched.o] Error 1
> make: *** [kernel] Error 2
>

You'll need this:

From: "Siddha, Suresh B" <suresh.b.siddha@intel.com>

Move trigger_load_balance() under ifdef CONFIG_SMP.

Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

kernel/sched.c | 124 +++++++++++++++++++++++------------------------
1 files changed, 62 insertions(+), 62 deletions(-)

diff -puN kernel/sched.c~sched-dynticks-idle-load-balancing-v3-fix kernel/sched.c
--- a/kernel/sched.c~sched-dynticks-idle-load-balancing-v3-fix
+++ a/kernel/sched.c
@@ -3130,6 +3130,68 @@ static void run_rebalance_domains(struct
}
#endif
}
+
+/*
+ * Trigger the SCHED_SOFTIRQ if it is time to do periodic load balancing.
+ *
+ * In case of CONFIG_NO_HZ, this is the place where we nominate a new
+ * idle load balancing owner or decide to stop the periodic load balancing,
+ * if the whole system is idle.
+ */
+static inline void trigger_load_balance(int cpu)
+{
+ struct rq *rq = cpu_rq(cpu);
+#ifdef CONFIG_NO_HZ
+ /*
+ * If we were in the nohz mode recently and busy at the current
+ * scheduler tick, then check if we need to nominate new idle
+ * load balancer.
+ */
+ if (rq->in_nohz_recently && !rq->idle_at_tick) {
+ rq->in_nohz_recently = 0;
+
+ if (atomic_read(&nohz.load_balancer) == cpu) {
+ cpu_clear(cpu, nohz.cpu_mask);
+ atomic_set(&nohz.load_balancer, -1);
+ }
+
+ if (atomic_read(&nohz.load_balancer) == -1) {
+ /*
+ * simple selection for now: Nominate the
+ * first cpu in the nohz list to be the next
+ * ilb owner.
+ *
+ * TBD: Traverse the sched domains and nominate
+ * the nearest cpu in the nohz.cpu_mask.
+ */
+ int ilb = first_cpu(nohz.cpu_mask);
+
+ if (ilb != NR_CPUS)
+ resched_cpu(ilb);
+ }
+ }
+
+ /*
+ * If this cpu is idle and doing idle load balancing for all the
+ * cpus with ticks stopped, is it time for that to stop?
+ */
+ if (rq->idle_at_tick && atomic_read(&nohz.load_balancer) == cpu &&
+ cpus_weight(nohz.cpu_mask) == num_online_cpus()) {
+ resched_cpu(cpu);
+ return;
+ }
+
+ /*
+ * If this cpu is idle and the idle load balancing is done by
+ * someone else, then no need raise the SCHED_SOFTIRQ
+ */
+ if (rq->idle_at_tick && atomic_read(&nohz.load_balancer) != cpu &&
+ cpu_isset(cpu, nohz.cpu_mask))
+ return;
+#endif
+ if (time_after_eq(jiffies, rq->next_balance))
+ raise_softirq(SCHED_SOFTIRQ);
+}
#else
/*
* on UP we do not need to balance between CPUs:
@@ -3340,68 +3402,6 @@ out_unlock:
}

/*
- * Trigger the SCHED_SOFTIRQ if it is time to do periodic load balancing.
- *
- * In case of CONFIG_NO_HZ, this is the place where we nominate a new
- * idle load balancing owner or decide to stop the periodic load balancing,
- * if the whole system is idle.
- */
-static inline void trigger_load_balance(int cpu)
-{
- struct rq *rq = cpu_rq(cpu);
-#ifdef CONFIG_NO_HZ
- /*
- * If we were in the nohz mode recently and busy at the current
- * scheduler tick, then check if we need to nominate new idle
- * load balancer.
- */
- if (rq->in_nohz_recently && !rq->idle_at_tick) {
- rq->in_nohz_recently = 0;
-
- if (atomic_read(&nohz.load_balancer) == cpu) {
- cpu_clear(cpu, nohz.cpu_mask);
- atomic_set(&nohz.load_balancer, -1);
- }
-
- if (atomic_read(&nohz.load_balancer) == -1) {
- /*
- * simple selection for now: Nominate the
- * first cpu in the nohz list to be the next
- * ilb owner.
- *
- * TBD: Traverse the sched domains and nominate
- * the nearest cpu in the nohz.cpu_mask.
- */
- int ilb = first_cpu(nohz.cpu_mask);
-
- if (ilb != NR_CPUS)
- resched_cpu(ilb);
- }
- }
-
- /*
- * If this cpu is idle and doing idle load balancing for all the
- * cpus with ticks stopped, is it time for that to stop?
- */
- if (rq->idle_at_tick && atomic_read(&nohz.load_balancer) == cpu &&
- cpus_weight(nohz.cpu_mask) == num_online_cpus()) {
- resched_cpu(cpu);
- return;
- }
-
- /*
- * If this cpu is idle and the idle load balancing is done by
- * someone else, then no need raise the SCHED_SOFTIRQ
- */
- if (rq->idle_at_tick && atomic_read(&nohz.load_balancer) != cpu &&
- cpu_isset(cpu, nohz.cpu_mask))
- return;
-#endif
- if (time_after_eq(jiffies, rq->next_balance))
- raise_softirq(SCHED_SOFTIRQ);
-}
-
-/*
* This function gets called by the timer code, with HZ frequency.
* We call it with interrupts disabled.
*
_