Merge branch 'sched-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull scheduler changes for v3.4 from Ingo Molnar

* 'sched-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (27 commits)
  printk: Make it compile with !CONFIG_PRINTK
  sched/x86: Fix overflow in cyc2ns_offset
  sched: Fix nohz load accounting -- again!
  sched: Update yield() docs
  printk/sched: Introduce special printk_sched() for those awkward moments
  sched/nohz: Correctly initialize 'next_balance' in 'nohz' idle balancer
  sched: Cleanup cpu_active madness
  sched: Fix load-balance wreckage
  sched: Clean up parameter passing of proc_sched_autogroup_set_nice()
  sched: Ditch per cgroup task lists for load-balancing
  sched: Rename load-balancing fields
  sched: Move load-balancing arguments into helper struct
  sched/rt: Do not submit new work when PI-blocked
  sched/rt: Prevent idle task boosting
  sched/wait: Add __wake_up_all_locked() API
  sched/rt: Document scheduler related skip-resched-check sites
  sched/rt: Use schedule_preempt_disabled()
  sched/rt: Add schedule_preempt_disabled()
  sched/rt: Do not throttle when PI boosting
  sched/rt: Keep period timer ticking when rt throttling is active
  ...

1 files changed, 37 insertions, 3 deletions

diff --git a/kernel/printk.c b/kernel/printk.c
index 0b3ea2cbd5fb..b663c2c95d39 100644
--- a/kernel/printk.c
+++ b/kernel/printk.c
@@ -1216,13 +1216,27 @@ int is_console_locked(void)
 	return console_locked;
 }
 
+/*
+ * Delayed printk facility, for scheduler-internal messages:
+ */
+#define PRINTK_BUF_SIZE		512
+
+#define PRINTK_PENDING_WAKEUP	0x01
+#define PRINTK_PENDING_SCHED	0x02
+
 static DEFINE_PER_CPU(int, printk_pending);
+static DEFINE_PER_CPU(char [PRINTK_BUF_SIZE], printk_sched_buf);
 
 void printk_tick(void)
 {
 	if (__this_cpu_read(printk_pending)) {
-		__this_cpu_write(printk_pending, 0);
-		wake_up_interruptible(&log_wait);
+		int pending = __this_cpu_xchg(printk_pending, 0);
+		if (pending & PRINTK_PENDING_SCHED) {
+			char *buf = __get_cpu_var(printk_sched_buf);
+			printk(KERN_WARNING "[sched_delayed] %s", buf);
+		}
+		if (pending & PRINTK_PENDING_WAKEUP)
+			wake_up_interruptible(&log_wait);
 	}
 }
 
@@ -1236,7 +1250,7 @@ int printk_needs_cpu(int cpu)
 void wake_up_klogd(void)
 {
 	if (waitqueue_active(&log_wait))
-		this_cpu_write(printk_pending, 1);
+		this_cpu_or(printk_pending, PRINTK_PENDING_WAKEUP);
 }
 
 /**
@@ -1629,6 +1643,26 @@ late_initcall(printk_late_init);
 
 #if defined CONFIG_PRINTK
 
+int printk_sched(const char *fmt, ...)
+{
+	unsigned long flags;
+	va_list args;
+	char *buf;
+	int r;
+
+	local_irq_save(flags);
+	buf = __get_cpu_var(printk_sched_buf);
+
+	va_start(args, fmt);
+	r = vsnprintf(buf, PRINTK_BUF_SIZE, fmt, args);
+	va_end(args);
+
+	__this_cpu_or(printk_pending, PRINTK_PENDING_SCHED);
+	local_irq_restore(flags);
+
+	return r;
+}
+
 /*
  * printk rate limiting, lifted from the networking subsystem.
  *