Merge branch 'core/urgent' into core/locking

[~andy/linux] / kernel / softirq.c

diff --git a/kernel/softirq.c b/kernel/softirq.c
index 11025ccc06dd1e2211ca62dcbcea7ce1b05418dd..f84aa48c0e6663de619daa869f6a1274e0cc5b50 100644 (file)
--- a/kernel/softirq.c
+++ b/kernel/softirq.c
@@ -211,14 +211,52 @@ EXPORT_SYMBOL(local_bh_enable_ip);
 #define MAX_SOFTIRQ_TIME  msecs_to_jiffies(2)
 #define MAX_SOFTIRQ_RESTART 10
 
+#ifdef CONFIG_TRACE_IRQFLAGS
+/*
+ * Convoluted means of passing __do_softirq() a message through the various
+ * architecture execute_on_stack() bits.
+ *
+ * When we run softirqs from irq_exit() and thus on the hardirq stack we need
+ * to keep the lockdep irq context tracking as tight as possible in order to
+ * not miss-qualify lock contexts and miss possible deadlocks.
+ */
+static DEFINE_PER_CPU(int, softirq_from_hardirq);
+
+static inline void lockdep_softirq_from_hardirq(void)
+{
+       this_cpu_write(softirq_from_hardirq, 1);
+}
+
+static inline void lockdep_softirq_start(void)
+{
+       if (this_cpu_read(softirq_from_hardirq))
+               trace_hardirq_exit();
+       lockdep_softirq_enter();
+}
+
+static inline void lockdep_softirq_end(void)
+{
+       lockdep_softirq_exit();
+       if (this_cpu_read(softirq_from_hardirq)) {
+               this_cpu_write(softirq_from_hardirq, 0);
+               trace_hardirq_enter();
+       }
+}
+
+#else
+static inline void lockdep_softirq_from_hardirq(void) { }
+static inline void lockdep_softirq_start(void) { }
+static inline void lockdep_softirq_end(void) { }
+#endif
+
 asmlinkage void __do_softirq(void)
 {
-       struct softirq_action *h;
-       __u32 pending;
        unsigned long end = jiffies + MAX_SOFTIRQ_TIME;
-       int cpu;
        unsigned long old_flags = current->flags;
        int max_restart = MAX_SOFTIRQ_RESTART;
+       struct softirq_action *h;
+       __u32 pending;
+       int cpu;
 
        /*
         * Mask out PF_MEMALLOC s current task context is borrowed for the
@@ -231,7 +269,7 @@ asmlinkage void __do_softirq(void)
        account_irq_enter_time(current);
 
        __local_bh_disable(_RET_IP_, SOFTIRQ_OFFSET);
-       lockdep_softirq_enter();
+       lockdep_softirq_start();
 
        cpu = smp_processor_id();
 restart:
@@ -278,16 +316,13 @@ restart:
                wakeup_softirqd();
        }
 
-       lockdep_softirq_exit();
-
+       lockdep_softirq_end();
        account_irq_exit_time(current);
        __local_bh_enable(SOFTIRQ_OFFSET);
        WARN_ON_ONCE(in_interrupt());
        tsk_restore_flags(current, old_flags, PF_MEMALLOC);
 }
 
-
-
 asmlinkage void do_softirq(void)
 {
        __u32 pending;
@@ -330,6 +365,7 @@ void irq_enter(void)
 static inline void invoke_softirq(void)
 {
        if (!force_irqthreads) {
+               lockdep_softirq_from_hardirq();
 #ifdef CONFIG_HAVE_IRQ_EXIT_ON_IRQ_STACK
                /*
                 * We can safely execute softirq on the current stack if
@@ -375,13 +411,13 @@ void irq_exit(void)
 #endif
 
        account_irq_exit_time(current);
-       trace_hardirq_exit();
        preempt_count_sub(HARDIRQ_OFFSET);
        if (!in_interrupt() && local_softirq_pending())
                invoke_softirq();
 
        tick_irq_exit();
        rcu_irq_exit();
+       trace_hardirq_exit(); /* must be last! */
 }
 
 /*