softirqs, debug: preemption check

if a preempt count leaks out of a softirq handler it can be very hard
to figure it out. Add a debug check for this.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

diff --git a/kernel/softirq.c b/kernel/softirq.c
index 82e32aa..1cf1e2f 100644 (file)
--- a/kernel/softirq.c
+++ b/kernel/softirq.c
@@ -205,7 +205,18 @@ restart:
 
        do {
                if (pending & 1) {
+                       int prev_count = preempt_count();
+
                        h->action(h);
+
+                       if (unlikely(prev_count != preempt_count())) {
+                               printk(KERN_ERR "huh, entered sotfirq %ld %p"
+                                      "with preempt_count %08x,"
+                                      " exited with %08x?\n", h - softirq_vec,
+                                      h->action, prev_count, preempt_count());
+                               preempt_count() = prev_count;
+                       }
+
                        rcu_bh_qsctr_inc(cpu);
                }
                h++;