From: Frederic Weisbecker <fweisbec@gmail.com>
Date: Mon, 4 Feb 2013 23:48:46 +0000 (+0100)
Subject: Merge branch 'nohz/printk-v8' into irq/core
X-Git-Url: http://git.lede-project.org./?a=commitdiff_plain;h=077931446b85e7858bf9dc0927cd116669b965d2;p=openwrt%2Fstaging%2Fblogic.git

Merge branch 'nohz/printk-v8' into irq/core

Conflicts:
	kernel/irq_work.c

Add support for printk in full dynticks CPU.

* Don't stop tick with irq works pending. This
fix is generally useful and concerns archs that
can't raise self IPIs.

* Flush irq works before CPU offlining.

* Introduce "lazy" irq works that can wait for the
next tick to be executed, unless it's stopped.

* Implement klogd wake up using irq work. This
removes the ad-hoc printk_tick()/printk_needs_cpu()
hooks and make it working even in dynticks mode.

Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
---

077931446b85e7858bf9dc0927cd116669b965d2
diff --cc kernel/irq_work.c
index c9d7478e4889,7f3a59bc8e3d..55fcce6065cf
--- a/kernel/irq_work.c
+++ b/kernel/irq_work.c
@@@ -63,37 -56,64 +56,53 @@@ void __weak arch_irq_work_raise(void
  }
  
  /*
 - * Queue the entry and raise the IPI if needed.
 + * Enqueue the irq_work @entry unless it's already pending
 + * somewhere.
 + *
 + * Can be re-enqueued while the callback is still in progress.
   */
 -static void __irq_work_queue(struct irq_work *work)
 +void irq_work_queue(struct irq_work *work)
  {
- 	bool empty;
- 
 +	/* Only queue if not already pending */
 +	if (!irq_work_claim(work))
 +		return;
 +
 +	/* Queue the entry and raise the IPI if needed. */
  	preempt_disable();
  
- 	empty = llist_add(&work->llnode, &__get_cpu_var(irq_work_list));
- 	/* The list was empty, raise self-interrupt to start processing. */
- 	if (empty)
- 		arch_irq_work_raise();
+ 	llist_add(&work->llnode, &__get_cpu_var(irq_work_list));
+ 
+ 	/*
+ 	 * If the work is not "lazy" or the tick is stopped, raise the irq
+ 	 * work interrupt (if supported by the arch), otherwise, just wait
+ 	 * for the next tick.
+ 	 */
+ 	if (!(work->flags & IRQ_WORK_LAZY) || tick_nohz_tick_stopped()) {
+ 		if (!this_cpu_cmpxchg(irq_work_raised, 0, 1))
+ 			arch_irq_work_raise();
+ 	}
  
  	preempt_enable();
  }
 -
 -/*
 - * Enqueue the irq_work @entry, returns true on success, failure when the
 - * @entry was already enqueued by someone else.
 - *
 - * Can be re-enqueued while the callback is still in progress.
 - */
 -bool irq_work_queue(struct irq_work *work)
 -{
 -	if (!irq_work_claim(work)) {
 -		/*
 -		 * Already enqueued, can't do!
 -		 */
 -		return false;
 -	}
 -
 -	__irq_work_queue(work);
 -	return true;
 -}
  EXPORT_SYMBOL_GPL(irq_work_queue);
  
- /*
-  * Run the irq_work entries on this cpu. Requires to be ran from hardirq
-  * context with local IRQs disabled.
-  */
- void irq_work_run(void)
+ bool irq_work_needs_cpu(void)
+ {
+ 	struct llist_head *this_list;
+ 
+ 	this_list = &__get_cpu_var(irq_work_list);
+ 	if (llist_empty(this_list))
+ 		return false;
+ 
+ 	/* All work should have been flushed before going offline */
+ 	WARN_ON_ONCE(cpu_is_offline(smp_processor_id()));
+ 
+ 	return true;
+ }
+ 
+ static void __irq_work_run(void)
  {
+ 	unsigned long flags;
  	struct irq_work *work;
  	struct llist_head *this_list;
  	struct llist_node *llnode;
diff --cc kernel/time/tick-sched.c
index d58e552d9fd1,822d7572bf2d..fb8e5e469d1c
--- a/kernel/time/tick-sched.c
+++ b/kernel/time/tick-sched.c
@@@ -28,10 -29,10 +29,10 @@@
  /*
   * Per cpu nohz control structure
   */
- static DEFINE_PER_CPU(struct tick_sched, tick_cpu_sched);
+ DEFINE_PER_CPU(struct tick_sched, tick_cpu_sched);
  
  /*
 - * The time, when the last jiffy update happened. Protected by xtime_lock.
 + * The time, when the last jiffy update happened. Protected by jiffies_lock.
   */
  static ktime_t last_jiffies_update;
  
@@@ -329,10 -287,10 +330,10 @@@ static ktime_t tick_nohz_stop_sched_tic
  		last_update = last_jiffies_update;
  		last_jiffies = jiffies;
  		time_delta = timekeeping_max_deferment();
 -	} while (read_seqretry(&xtime_lock, seq));
 +	} while (read_seqretry(&jiffies_lock, seq));
  
- 	if (rcu_needs_cpu(cpu, &rcu_delta_jiffies) || printk_needs_cpu(cpu) ||
- 	    arch_needs_cpu(cpu)) {
+ 	if (rcu_needs_cpu(cpu, &rcu_delta_jiffies) ||
+ 	    arch_needs_cpu(cpu) || irq_work_needs_cpu()) {
  		next_jiffies = last_jiffies + 1;
  		delta_jiffies = 1;
  	} else {