Merge branch 'irq-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git...

[karo-tx-linux.git] / kernel / softirq.c

diff --git a/kernel/softirq.c b/kernel/softirq.c
index a5f88362589bc6cccfffbacfbf1b7341bde19300..ca25e6e704a2f8ba1277fd3bd5975ed3518b09f7 100644 (file)
--- a/kernel/softirq.c
+++ b/kernel/softirq.c
@@ -194,8 +194,12 @@ void local_bh_enable_ip(unsigned long ip)
 EXPORT_SYMBOL(local_bh_enable_ip);
 
 /*
- * We restart softirq processing for at most 2 ms,
- * and if need_resched() is not set.
+ * We restart softirq processing for at most MAX_SOFTIRQ_RESTART times,
+ * but break the loop if need_resched() is set or after 2 ms.
+ * The MAX_SOFTIRQ_TIME provides a nice upper bound in most cases, but in
+ * certain cases, such as stop_machine(), jiffies may cease to
+ * increment and so we need the MAX_SOFTIRQ_RESTART limit as
+ * well to make sure we eventually return from this method.
  *
  * These limits have been established via experimentation.
  * The two things to balance is latency against fairness -
@@ -203,6 +207,7 @@ EXPORT_SYMBOL(local_bh_enable_ip);
  * should not be able to lock up the box.
  */
 #define MAX_SOFTIRQ_TIME  msecs_to_jiffies(2)
+#define MAX_SOFTIRQ_RESTART 10
 
 asmlinkage void __do_softirq(void)
 {
@@ -211,6 +216,7 @@ asmlinkage void __do_softirq(void)
        unsigned long end = jiffies + MAX_SOFTIRQ_TIME;
        int cpu;
        unsigned long old_flags = current->flags;
+       int max_restart = MAX_SOFTIRQ_RESTART;
 
        /*
         * Mask out PF_MEMALLOC s current task context is borrowed for the
@@ -263,7 +269,8 @@ restart:
 
        pending = local_softirq_pending();
        if (pending) {
-               if (time_before(jiffies, end) && !need_resched())
+               if (time_before(jiffies, end) && !need_resched() &&
+                   --max_restart)
                        goto restart;
 
                wakeup_softirqd();