softirq-split-out-code.patch

Subject: softirq-split-out-code.patch
From: Thomas Gleixner <tglx@linutronix.de>
Date: Tue, 28 Jun 2011 15:46:49 +0200

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
---
 kernel/softirq.c |   94 ++++++++++++++++++++++++++++++-------------------------
 1 file changed, 52 insertions(+), 42 deletions(-)

Index: linux-stable/kernel/softirq.c
===================================================================
--- linux-stable.orig/kernel/softirq.c
+++ linux-stable/kernel/softirq.c
@@ -76,6 +76,34 @@ static void wakeup_softirqd(void)
 		wake_up_process(tsk);
 }
 
+static void handle_pending_softirqs(u32 pending, int cpu)
+{
+	struct softirq_action *h = softirq_vec;
+	unsigned int prev_count = preempt_count();
+
+	local_irq_enable();
+	for ( ; pending; h++, pending >>= 1) {
+		unsigned int vec_nr = h - softirq_vec;
+
+		if (!(pending & 1))
+			continue;
+
+		kstat_incr_softirqs_this_cpu(vec_nr);
+		trace_softirq_entry(vec_nr);
+		h->action(h);
+		trace_softirq_exit(vec_nr);
+		if (unlikely(prev_count != preempt_count())) {
+			printk(KERN_ERR
+ "huh, entered softirq %u %s %p with preempt_count %08x exited with %08x?\n",
+			       vec_nr, softirq_to_name[vec_nr], h->action,
+			       prev_count, (unsigned int) preempt_count());
+			preempt_count() = prev_count;
+		}
+		rcu_bh_qs(cpu);
+	}
+	local_irq_disable();
+}
+
 /*
  * preempt_count and SOFTIRQ_OFFSET usage:
  * - preempt_count is changed by SOFTIRQ_OFFSET on entering or leaving
@@ -206,7 +234,6 @@ EXPORT_SYMBOL(local_bh_enable_ip);
 
 asmlinkage void __do_softirq(void)
 {
-	struct softirq_action *h;
 	__u32 pending;
 	int max_restart = MAX_SOFTIRQ_RESTART;
 	int cpu;
@@ -223,7 +250,7 @@ asmlinkage void __do_softirq(void)
 	account_system_vtime(current);
 
 	__local_bh_disable((unsigned long)__builtin_return_address(0),
-				SOFTIRQ_OFFSET);
+			   SOFTIRQ_OFFSET);
 	lockdep_softirq_enter();
 
 	cpu = smp_processor_id();
@@ -231,36 +258,7 @@ restart:
 	/* Reset the pending bitmask before enabling irqs */
 	set_softirq_pending(0);
 
-	local_irq_enable();
-
-	h = softirq_vec;
-
-	do {
-		if (pending & 1) {
-			unsigned int vec_nr = h - softirq_vec;
-			int prev_count = preempt_count();
-
-			kstat_incr_softirqs_this_cpu(vec_nr);
-
-			trace_softirq_entry(vec_nr);
-			h->action(h);
-			trace_softirq_exit(vec_nr);
-			if (unlikely(prev_count != preempt_count())) {
-				printk(KERN_ERR "huh, entered softirq %u %s %p"
-				       "with preempt_count %08x,"
-				       " exited with %08x?\n", vec_nr,
-				       softirq_to_name[vec_nr], h->action,
-				       prev_count, preempt_count());
-				preempt_count() = prev_count;
-			}
-
-			rcu_bh_qs(cpu);
-		}
-		h++;
-		pending >>= 1;
-	} while (pending);
-
-	local_irq_disable();
+	handle_pending_softirqs(pending, cpu);
 
 	pending = local_softirq_pending();
 	if (pending && --max_restart)
@@ -276,6 +274,26 @@ restart:
 	tsk_restore_flags(current, old_flags, PF_MEMALLOC);
 }
 
+/*
+ * Called with preemption disabled from run_ksoftirqd()
+ */
+static int ksoftirqd_do_softirq(int cpu)
+{
+	/*
+	 * Preempt disable stops cpu going offline.
+	 * If already offline, we'll be on wrong CPU:
+	 * don't process.
+	 */
+	if (cpu_is_offline(cpu))
+		return -1;
+
+	local_irq_disable();
+	if (local_softirq_pending())
+		__do_softirq();
+	local_irq_enable();
+	return 0;
+}
+
 #ifndef __ARCH_HAS_DO_SOFTIRQ
 
 asmlinkage void do_softirq(void)
@@ -748,22 +766,14 @@ static int run_ksoftirqd(void * __bind_c
 
 	while (!kthread_should_stop()) {
 		preempt_disable();
-		if (!local_softirq_pending()) {
+		if (!local_softirq_pending())
 			schedule_preempt_disabled();
-		}
 
 		__set_current_state(TASK_RUNNING);
 
 		while (local_softirq_pending()) {
-			/* Preempt disable stops cpu going offline.
-			   If already offline, we'll be on wrong CPU:
-			   don't process */
-			if (cpu_is_offline((long)__bind_cpu))
+			if (ksoftirqd_do_softirq((long) __bind_cpu))
 				goto wait_to_die;
-			local_irq_disable();
-			if (local_softirq_pending())
-				__do_softirq();
-			local_irq_enable();
 			sched_preempt_enable_no_resched();
 			cond_resched();
 			preempt_disable();