[PATCH V7 2/4] softirq: Factor loop termination condition

[qianjun . kernel]

From: jun qian <qianjun.ker...@gmail.com>

Add a function interface to end softirq process

Signed-off-by: jun qian <qianjun.ker...@gmail.com>
---
 kernel/softirq.c | 44 +++++++++++++++++++++++++-------------------
 1 file changed, 25 insertions(+), 19 deletions(-)

diff --git a/kernel/softirq.c b/kernel/softirq.c
index 0db77ab..5a627cd 100644
--- a/kernel/softirq.c
+++ b/kernel/softirq.c
@@ -198,22 +198,6 @@ void __local_bh_enable_ip(unsigned long ip, unsigned int 
cnt)
 }
 EXPORT_SYMBOL(__local_bh_enable_ip);
 
-/*
- * 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 -
- * we want to handle softirqs as soon as possible, but they
- * should not be able to lock up the box.
- */
-#define MAX_SOFTIRQ_TIME       (2 * NSEC_PER_MSEC)
-#define MAX_SOFTIRQ_RESTART 10
-
 #ifdef CONFIG_TRACE_IRQFLAGS
 /*
  * When we run softirqs from irq_exit() and thus on the hardirq stack we need
@@ -247,11 +231,34 @@ static inline void lockdep_softirq_end(bool in_hardirq)
 static inline void lockdep_softirq_end(bool in_hardirq) { }
 #endif
 
+/*
+ * We restart softirq processing but break the loop if need_resched() is
+ * set or after 2 ms. The MAX_SOFTIRQ_RESTART guarantees a loop termination
+ * if sched_clock() were ever to stall.
+ *
+ * These limits have been established via experimentation.  The two things
+ * to balance is latency against fairness - we want to handle softirqs as
+ * soon as possible, but they should not be able to lock up the box.
+ */
+#define MAX_SOFTIRQ_TIME       (2 * NSEC_PER_MSEC)
+#define MAX_SOFTIRQ_RESTART    10
+
+static inline bool __softirq_needs_break(u64 start)
+{
+       if (need_resched())
+               return true;
+
+       if (sched_clock() - start >= MAX_SOFTIRQ_TIME)
+               return true;
+
+       return false;
+}
+
 asmlinkage __visible void __softirq_entry __do_softirq(void)
 {
        u64 start = sched_clock();
        unsigned long old_flags = current->flags;
-       int max_restart = MAX_SOFTIRQ_RESTART;
+       unsigned int max_restart = MAX_SOFTIRQ_RESTART;
        struct softirq_action *h;
        bool in_hardirq;
        __u32 pending;
@@ -308,8 +315,7 @@ asmlinkage __visible void __softirq_entry __do_softirq(void)
 
        pending = local_softirq_pending();
        if (pending) {
-               if (sched_clock() - start < MAX_SOFTIRQ_TIME && !need_resched() 
&&
-                   --max_restart)
+               if (!__softirq_needs_break(start) && --max_restart)
                        goto restart;
 
                wakeup_softirqd();
-- 
1.8.3.1