1 files changed, 54 insertions, 28 deletions

diff --git a/kernel/softirq.c b/kernel/softirq.c
index d19b1c9aa7c5..18f4be0d5fe0 100644
--- a/kernel/softirq.c
+++ b/kernel/softirq.c
@@ -67,7 +67,7 @@ char *softirq_to_name[NR_SOFTIRQS] = {
  * to the pending events, so lets the scheduler to balance
  * the softirq load for us.
  */
-void wakeup_softirqd(void)
+static void wakeup_softirqd(void)
 {
         /* Interrupts are disabled: no need to stop preemption */
         struct task_struct *tsk = __get_cpu_var(ksoftirqd);
@@ -77,11 +77,21 @@ void wakeup_softirqd(void)
 }
 
 /*
+ * preempt_count and SOFTIRQ_OFFSET usage:
+ * - preempt_count is changed by SOFTIRQ_OFFSET on entering or leaving
+ *   softirq processing.
+ * - preempt_count is changed by SOFTIRQ_DISABLE_OFFSET (= 2 * SOFTIRQ_OFFSET)
+ *   on local_bh_disable or local_bh_enable.
+ * This lets us distinguish between whether we are currently processing
+ * softirq and whether we just have bh disabled.
+ */
+
+/*
  * This one is for softirq.c-internal use,
  * where hardirqs are disabled legitimately:
  */
 #ifdef CONFIG_TRACE_IRQFLAGS
-static void __local_bh_disable(unsigned long ip)
+static void __local_bh_disable(unsigned long ip, unsigned int cnt)
 {
         unsigned long flags;
 
@@ -95,32 +105,43 @@ static void __local_bh_disable(unsigned long ip)
          * We must manually increment preempt_count here and manually
          * call the trace_preempt_off later.
          */
-        preempt_count() += SOFTIRQ_OFFSET;
+        preempt_count() += cnt;
         /*
          * Were softirqs turned off above:
          */
-        if (softirq_count() == SOFTIRQ_OFFSET)
+        if (softirq_count() == cnt)
                 trace_softirqs_off(ip);
         raw_local_irq_restore(flags);
 
-        if (preempt_count() == SOFTIRQ_OFFSET)
+        if (preempt_count() == cnt)
                 trace_preempt_off(CALLER_ADDR0, get_parent_ip(CALLER_ADDR1));
 }
 #else /* !CONFIG_TRACE_IRQFLAGS */
-static inline void __local_bh_disable(unsigned long ip)
+static inline void __local_bh_disable(unsigned long ip, unsigned int cnt)
 {
-        add_preempt_count(SOFTIRQ_OFFSET);
+        add_preempt_count(cnt);
         barrier();
 }
 #endif /* CONFIG_TRACE_IRQFLAGS */
 
 void local_bh_disable(void)
 {
-        __local_bh_disable((unsigned long)__builtin_return_address(0));
+        __local_bh_disable((unsigned long)__builtin_return_address(0),
+                                SOFTIRQ_DISABLE_OFFSET);
 }
 
 EXPORT_SYMBOL(local_bh_disable);
 
+static void __local_bh_enable(unsigned int cnt)
+{
+        WARN_ON_ONCE(in_irq());
+        WARN_ON_ONCE(!irqs_disabled());
+
+        if (softirq_count() == cnt)
+                trace_softirqs_on((unsigned long)__builtin_return_address(0));
+        sub_preempt_count(cnt);
+}
+
 /*
  * Special-case - softirqs can safely be enabled in
  * cond_resched_softirq(), or by __do_softirq(),
@@ -128,12 +149,7 @@ EXPORT_SYMBOL(local_bh_disable);
  */
 void _local_bh_enable(void)
 {
-        WARN_ON_ONCE(in_irq());
-        WARN_ON_ONCE(!irqs_disabled());
-
-        if (softirq_count() == SOFTIRQ_OFFSET)
-                trace_softirqs_on((unsigned long)__builtin_return_address(0));
-        sub_preempt_count(SOFTIRQ_OFFSET);
+        __local_bh_enable(SOFTIRQ_DISABLE_OFFSET);
 }
 
 EXPORT_SYMBOL(_local_bh_enable);
@@ -147,13 +163,13 @@ static inline void _local_bh_enable_ip(unsigned long ip)
         /*
          * Are softirqs going to be turned on now:
          */
-        if (softirq_count() == SOFTIRQ_OFFSET)
+        if (softirq_count() == SOFTIRQ_DISABLE_OFFSET)
                 trace_softirqs_on(ip);
         /*
          * Keep preemption disabled until we are done with
          * softirq processing:
          */
-        sub_preempt_count(SOFTIRQ_OFFSET - 1);
+        sub_preempt_count(SOFTIRQ_DISABLE_OFFSET - 1);
 
         if (unlikely(!in_interrupt() && local_softirq_pending()))
                 do_softirq();
@@ -198,7 +214,8 @@ asmlinkage void __do_softirq(void)
         pending = local_softirq_pending();
         account_system_vtime(current);
 
-        __local_bh_disable((unsigned long)__builtin_return_address(0));
+        __local_bh_disable((unsigned long)__builtin_return_address(0),
+                                SOFTIRQ_OFFSET);
         lockdep_softirq_enter();
 
         cpu = smp_processor_id();
@@ -212,18 +229,20 @@ restart:
 
         do {
                 if (pending & 1) {
+                        unsigned int vec_nr = h - softirq_vec;
                         int prev_count = preempt_count();
-                        kstat_incr_softirqs_this_cpu(h - softirq_vec);
 
-                        trace_softirq_entry(h, softirq_vec);
+                        kstat_incr_softirqs_this_cpu(vec_nr);
+
+                        trace_softirq_entry(vec_nr);
                         h->action(h);
-                        trace_softirq_exit(h, softirq_vec);
+                        trace_softirq_exit(vec_nr);
                         if (unlikely(prev_count != preempt_count())) {
-                                printk(KERN_ERR "huh, entered softirq %td %s %p"
+                                printk(KERN_ERR "huh, entered softirq %u %s %p"
                                        "with preempt_count %08x,"
-                                       " exited with %08x?\n", h - softirq_vec,
-                                       softirq_to_name[h - softirq_vec],
-                                       h->action, prev_count, preempt_count());
+                                       " exited with %08x?\n", vec_nr,
+                                       softirq_to_name[vec_nr], h->action,
+                                       prev_count, preempt_count());
                                 preempt_count() = prev_count;
                         }
 
@@ -245,7 +264,7 @@ restart:
         lockdep_softirq_exit();
 
         account_system_vtime(current);
-        _local_bh_enable();
+        __local_bh_enable(SOFTIRQ_OFFSET);
 }
 
 #ifndef __ARCH_HAS_DO_SOFTIRQ
@@ -279,10 +298,16 @@ void irq_enter(void)
 
         rcu_irq_enter();
         if (idle_cpu(cpu) && !in_interrupt()) {
-                __irq_enter();
+                /*
+                 * Prevent raise_softirq from needlessly waking up ksoftirqd
+                 * here, as softirq will be serviced on return from interrupt.
+                 */
+                local_bh_disable();
                 tick_check_idle(cpu);
-        } else
-                __irq_enter();
+                _local_bh_enable();
+        }
+
+        __irq_enter();
 }
 
 #ifdef __ARCH_IRQ_EXIT_IRQS_DISABLED
@@ -696,6 +721,7 @@ static int run_ksoftirqd(void * __bind_cpu)
 {
         set_current_state(TASK_INTERRUPTIBLE);
 
+        current->flags |= PF_KSOFTIRQD;
         while (!kthread_should_stop()) {
                 preempt_disable();
                 if (!local_softirq_pending()) {