EXPORT_SYMBOL(local_bh_enable_ip);
/*
- * We restart softirq processing MAX_SOFTIRQ_RESTART times,
- * and we fall back to softirqd after that.
+ * 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.
*
- * This number has been established via experimentation.
+ * 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 msecs_to_jiffies(2)
#define MAX_SOFTIRQ_RESTART 10
asmlinkage void __do_softirq(void)
{
struct softirq_action *h;
__u32 pending;
- int max_restart = MAX_SOFTIRQ_RESTART;
+ unsigned long end = jiffies + MAX_SOFTIRQ_TIME;
int cpu;
+ int max_restart = MAX_SOFTIRQ_RESTART;
pending = local_softirq_pending();
account_system_vtime(current);
local_irq_disable();
pending = local_softirq_pending();
- if (pending && --max_restart)
- goto restart;
+ if (pending) {
+ if (time_before(jiffies, end) && !need_resched() &&
+ --max_restart)
+ goto restart;
- if (pending)
wakeup_softirqd();
+ }
lockdep_softirq_exit();