176 lines
5.0 KiB
Diff
176 lines
5.0 KiB
Diff
Subject: softirq: Adapt NOHZ softirq pending check to new RT scheme
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From: Thomas Gleixner <tglx@linutronix.de>
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Date: Sun, 28 Oct 2012 13:46:16 +0000
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Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/3.12/patches-3.12.1-rt4.tar.xz
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We can't rely on ksoftirqd anymore and we need to check the tasks
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which run a particular softirq and if such a task is pi blocked ignore
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the other pending bits of that task as well.
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Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
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---
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kernel/softirq.c | 83 ++++++++++++++++++++++++++++++++++++++-----------------
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1 file changed, 58 insertions(+), 25 deletions(-)
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--- a/kernel/softirq.c
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+++ b/kernel/softirq.c
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@@ -66,46 +66,71 @@ char *softirq_to_name[NR_SOFTIRQS] = {
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#ifdef CONFIG_NO_HZ_COMMON
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# ifdef CONFIG_PREEMPT_RT_FULL
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+
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+struct softirq_runner {
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+ struct task_struct *runner[NR_SOFTIRQS];
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+};
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+
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+static DEFINE_PER_CPU(struct softirq_runner, softirq_runners);
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+
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+static inline void softirq_set_runner(unsigned int sirq)
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+{
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+ struct softirq_runner *sr = &__get_cpu_var(softirq_runners);
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+
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+ sr->runner[sirq] = current;
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+}
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+
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+static inline void softirq_clr_runner(unsigned int sirq)
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+{
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+ struct softirq_runner *sr = &__get_cpu_var(softirq_runners);
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+
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+ sr->runner[sirq] = NULL;
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+}
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+
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/*
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- * On preempt-rt a softirq might be blocked on a lock. There might be
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- * no other runnable task on this CPU because the lock owner runs on
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- * some other CPU. So we have to go into idle with the pending bit
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- * set. Therefor we need to check this otherwise we warn about false
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- * positives which confuses users and defeats the whole purpose of
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- * this test.
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+ * On preempt-rt a softirq running context might be blocked on a
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+ * lock. There might be no other runnable task on this CPU because the
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+ * lock owner runs on some other CPU. So we have to go into idle with
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+ * the pending bit set. Therefor we need to check this otherwise we
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+ * warn about false positives which confuses users and defeats the
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+ * whole purpose of this test.
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*
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* This code is called with interrupts disabled.
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*/
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void softirq_check_pending_idle(void)
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{
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static int rate_limit;
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- u32 warnpending = 0, pending;
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+ struct softirq_runner *sr = &__get_cpu_var(softirq_runners);
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+ u32 warnpending;
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+ int i;
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if (rate_limit >= 10)
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return;
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- pending = local_softirq_pending() & SOFTIRQ_STOP_IDLE_MASK;
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- if (pending) {
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- struct task_struct *tsk;
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+ warnpending = local_softirq_pending() & SOFTIRQ_STOP_IDLE_MASK;
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+ for (i = 0; i < NR_SOFTIRQS; i++) {
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+ struct task_struct *tsk = sr->runner[i];
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- tsk = __get_cpu_var(ksoftirqd);
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/*
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* The wakeup code in rtmutex.c wakes up the task
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* _before_ it sets pi_blocked_on to NULL under
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* tsk->pi_lock. So we need to check for both: state
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* and pi_blocked_on.
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*/
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- raw_spin_lock(&tsk->pi_lock);
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-
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- if (!tsk->pi_blocked_on && !(tsk->state == TASK_RUNNING))
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- warnpending = 1;
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-
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- raw_spin_unlock(&tsk->pi_lock);
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+ if (tsk) {
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+ raw_spin_lock(&tsk->pi_lock);
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+ if (tsk->pi_blocked_on || tsk->state == TASK_RUNNING) {
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+ /* Clear all bits pending in that task */
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+ warnpending &= ~(tsk->softirqs_raised);
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+ warnpending &= ~(1 << i);
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+ }
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+ raw_spin_unlock(&tsk->pi_lock);
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+ }
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}
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if (warnpending) {
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printk(KERN_ERR "NOHZ: local_softirq_pending %02x\n",
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- pending);
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+ warnpending);
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rate_limit++;
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}
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}
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@@ -125,6 +150,10 @@ void softirq_check_pending_idle(void)
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}
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}
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# endif
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+
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+#else /* !CONFIG_NO_HZ_COMMON */
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+static inline void softirq_set_runner(unsigned int sirq) { }
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+static inline void softirq_clr_runner(unsigned int sirq) { }
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#endif
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/*
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@@ -521,6 +550,7 @@ static void do_current_softirqs(int need
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*/
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lock_softirq(i);
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local_irq_disable();
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+ softirq_set_runner(i);
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/*
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* Check with the local_softirq_pending() bits,
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* whether we need to process this still or if someone
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@@ -531,6 +561,7 @@ static void do_current_softirqs(int need
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set_softirq_pending(pending & ~mask);
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do_single_softirq(i, need_rcu_bh_qs);
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}
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+ softirq_clr_runner(i);
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unlock_softirq(i);
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WARN_ON(current->softirq_nestcnt != 1);
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}
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@@ -601,7 +632,7 @@ void thread_do_softirq(void)
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}
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}
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-void __raise_softirq_irqoff(unsigned int nr)
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+static void do_raise_softirq_irqoff(unsigned int nr)
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{
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trace_softirq_raise(nr);
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or_softirq_pending(1UL << nr);
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@@ -618,12 +649,19 @@ void __raise_softirq_irqoff(unsigned int
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__this_cpu_read(ksoftirqd)->softirqs_raised |= (1U << nr);
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}
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+void __raise_softirq_irqoff(unsigned int nr)
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+{
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+ do_raise_softirq_irqoff(nr);
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+ if (!in_irq() && !current->softirq_nestcnt)
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+ wakeup_softirqd();
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+}
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+
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/*
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* This function must run with irqs disabled!
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*/
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void raise_softirq_irqoff(unsigned int nr)
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{
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- __raise_softirq_irqoff(nr);
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+ do_raise_softirq_irqoff(nr);
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/*
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* If we're in an hard interrupt we let irq return code deal
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@@ -645,11 +683,6 @@ void raise_softirq_irqoff(unsigned int n
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wakeup_softirqd();
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}
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-void do_raise_softirq_irqoff(unsigned int nr)
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-{
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- raise_softirq_irqoff(nr);
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-}
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-
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static inline int ksoftirqd_softirq_pending(void)
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{
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return current->softirqs_raised;
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