[patch 3/7] softirq: avoid softirq_work_list for SCHED_SOFTIRQ when sent remotely

[Suresh Siddha <suresh.b.siddha@intel.com>]

[-- Attachment #1: fix_local_trigger_remote_softirq_for_sched.patch --]
[-- Type: text/plain, Size: 1141 bytes --]

There is no need to add the SCHED_SOFTIRQ work to the softirq_work_list
when sent remotely. This is because any pending work associated with
SCHED_SOFTIRQ need not be migrated to a new cpu when the current cpu is
going down etc.

Also I am not sure how this softirq_work_list works for other softirqs.
I don't see anyone removing the list entries from the softirq_work_list
after it is handled on a remote cpu.

For now, just skip it for SCHED_SOFTIRQ.

Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com>
Cc: David S. Miller <davem@davemloft.net>
Cc: Jens Axboe <jens.axboe@oracle.com>
---
 kernel/softirq.c |    5 +++++
 1 file changed, 5 insertions(+)

Index: tip/kernel/softirq.c
===================================================================
--- tip.orig/kernel/softirq.c
+++ tip/kernel/softirq.c
@@ -557,6 +557,11 @@ static void __local_trigger(struct call_
 {
 	struct list_head *head = &__get_cpu_var(softirq_work_list[softirq]);
 
+	if (softirq == SCHED_SOFTIRQ) {
+		raise_softirq_irqoff(softirq);
+		return;
+	}
+
 	list_add_tail(&cp->list, head);
 
 	/* Trigger the softirq only if the list was previously empty.  */