diff options
author | Thomas Gleixner <tglx@linutronix.de> | 2009-07-03 13:16:38 -0500 |
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committer | Clark Williams <williams@redhat.com> | 2012-03-13 12:40:09 -0500 |
commit | 2b7a57cc9da54987ab893e885ad1c99808d2d285 (patch) | |
tree | f531e3db4912dfeabfd57adc6739c0af61a49fc5 /kernel/softirq.c | |
parent | fc464c633c867d2568d87c43e66bcac21a6215da (diff) |
softirq: Sanitize softirq pending for NOHZ/RT
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Diffstat (limited to 'kernel/softirq.c')
-rw-r--r-- | kernel/softirq.c | 61 |
1 files changed, 61 insertions, 0 deletions
diff --git a/kernel/softirq.c b/kernel/softirq.c index c6c58240d267..83326220d049 100644 --- a/kernel/softirq.c +++ b/kernel/softirq.c @@ -61,6 +61,67 @@ char *softirq_to_name[NR_SOFTIRQS] = { "TASKLET", "SCHED", "HRTIMER", "RCU" }; +#ifdef CONFIG_NO_HZ +# ifdef CONFIG_PREEMPT_RT_FULL +/* + * On preempt-rt a softirq might be blocked on a lock. There might be + * no other runnable task on this CPU because the lock owner runs on + * some other CPU. So we have to go into idle with the pending bit + * set. Therefor we need to check this otherwise we warn about false + * positives which confuses users and defeats the whole purpose of + * this test. + * + * This code is called with interrupts disabled. + */ +void softirq_check_pending_idle(void) +{ + static int rate_limit; + u32 warnpending = 0, pending = local_softirq_pending(); + + if (rate_limit >= 10) + return; + + if (pending) { + struct task_struct *tsk; + + tsk = __get_cpu_var(ksoftirqd); + /* + * The wakeup code in rtmutex.c wakes up the task + * _before_ it sets pi_blocked_on to NULL under + * tsk->pi_lock. So we need to check for both: state + * and pi_blocked_on. + */ + raw_spin_lock(&tsk->pi_lock); + + if (!tsk->pi_blocked_on && !(tsk->state == TASK_RUNNING)) + warnpending = 1; + + raw_spin_unlock(&tsk->pi_lock); + } + + if (warnpending) { + printk(KERN_ERR "NOHZ: local_softirq_pending %02x\n", + pending); + rate_limit++; + } +} +# else +/* + * On !PREEMPT_RT we just printk rate limited: + */ +void softirq_check_pending_idle(void) +{ + static int rate_limit; + + if (rate_limit < 10) { + printk(KERN_ERR "NOHZ: local_softirq_pending %02x\n", + local_softirq_pending()); + rate_limit++; + } +} +# endif +#endif + /* * we cannot loop indefinitely here to avoid userspace starvation, * but we also don't want to introduce a worst case 1/HZ latency |