Merge branch 'v3.10/topic/configs' of git://git.linaro.org/kernel/linux-linaro-stable...

[firefly-linux-kernel-4.4.55.git] / kernel / softirq.c

diff --git a/kernel/softirq.c b/kernel/softirq.c
index aa82723c72027a86e67914e8a7b765613c06fbc6..787b3a032429a7a88321caf473f6f0e75d12da87 100644 (file)
--- a/kernel/softirq.c
+++ b/kernel/softirq.c
@@ -195,8 +195,12 @@ 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 -
@@ -204,6 +208,7 @@ 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)
 {
@@ -212,6 +217,7 @@ 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
@@ -265,7 +271,8 @@ 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();
@@ -323,10 +330,32 @@ void irq_enter(void)
 
 static inline void invoke_softirq(void)
 {
-       if (!force_irqthreads)
-               __do_softirq();
-       else
+       if (!force_irqthreads) {
+               /*
+                * We can safely execute softirq on the current stack if
+                * it is the irq stack, because it should be near empty
+                * at this stage. But we have no way to know if the arch
+                * calls irq_exit() on the irq stack. So call softirq
+                * in its own stack to prevent from any overrun on top
+                * of a potentially deep task stack.
+                */
+               do_softirq();
+       } else {
                wakeup_softirqd();
+       }
+}
+
+static inline void tick_irq_exit(void)
+{
+#ifdef CONFIG_NO_HZ_COMMON
+       int cpu = smp_processor_id();
+
+       /* Make sure that timer wheel updates are propagated */
+       if ((idle_cpu(cpu) && !need_resched()) || tick_nohz_full_cpu(cpu)) {
+               if (!in_interrupt())
+                       tick_nohz_irq_exit();
+       }
+#endif
 }
 
 /*
@@ -346,11 +375,7 @@ void irq_exit(void)
        if (!in_interrupt() && local_softirq_pending())
                invoke_softirq();
 
-#ifdef CONFIG_NO_HZ
-       /* Make sure that timer wheel updates are propagated */
-       if (idle_cpu(smp_processor_id()) && !in_interrupt() && !need_resched())
-               tick_nohz_irq_exit();
-#endif
+       tick_irq_exit();
        rcu_irq_exit();
 }