patches/0212-console-make-rt-friendly.patch.patch

From 74fe126d049e32879b59736aca0a1fff0269934b Mon Sep 17 00:00:00 2001
From: Thomas Gleixner <tglx@linutronix.de>
Date: Sun, 17 Jul 2011 22:43:07 +0200
Subject: [PATCH 212/274] console-make-rt-friendly.patch

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
---
 kernel/printk.c |   26 +++++++++++++++++++++++---
 1 file changed, 23 insertions(+), 3 deletions(-)

diff --git a/kernel/printk.c b/kernel/printk.c
index 9a27a94..28baa36 100644
--- a/kernel/printk.c
+++ b/kernel/printk.c
@@ -507,6 +507,7 @@ static void __call_console_drivers(unsigned start, unsigned end)
 {
 	struct console *con;
 
+	migrate_disable();
 	for_each_console(con) {
 		if (exclusive_console && con != exclusive_console)
 			continue;
@@ -515,6 +516,7 @@ static void __call_console_drivers(unsigned start, unsigned end)
 				(con->flags & CON_ANYTIME)))
 			con->write(con, &LOG_BUF(start), end - start);
 	}
+	migrate_enable();
 }
 
 #ifdef CONFIG_EARLY_PRINTK
@@ -839,12 +841,18 @@ static inline int can_use_console(unsigned int cpu)
  * interrupts disabled. It should return with 'lockbuf_lock'
  * released but interrupts still disabled.
  */
-static int console_trylock_for_printk(unsigned int cpu)
+static int console_trylock_for_printk(unsigned int cpu, unsigned long flags)
 	__releases(&logbuf_lock)
 {
 	int retval = 0, wake = 0;
+#ifdef CONFIG_PREEMPT_RT_FULL
+	int lock = !early_boot_irqs_disabled && !irqs_disabled_flags(flags) &&
+		!preempt_count();
+#else
+	int lock = 1;
+#endif
 
-	if (console_trylock()) {
+	if (lock && console_trylock()) {
 		retval = 1;
 
 		/*
@@ -1021,8 +1029,15 @@ asmlinkage int vprintk(const char *fmt, va_list args)
 	 * will release 'logbuf_lock' regardless of whether it
 	 * actually gets the semaphore or not.
 	 */
-	if (console_trylock_for_printk(this_cpu))
+	if (console_trylock_for_printk(this_cpu, flags)) {
+#ifndef CONFIG_PREEMPT_RT_FULL
 		console_unlock();
+#else
+		raw_local_irq_restore(flags);
+		console_unlock();
+		raw_local_irq_save(flags);
+#endif
+	}
 
 	lockdep_on();
 out_restore_irqs:
@@ -1345,11 +1360,16 @@ again:
 		_con_start = con_start;
 		_log_end = log_end;
 		con_start = log_end;		/* Flush */
+#ifndef CONFIG_PREEMPT_RT_FULL
 		raw_spin_unlock(&logbuf_lock);
 		stop_critical_timings();	/* don't trace print latency */
 		call_console_drivers(_con_start, _log_end);
 		start_critical_timings();
 		local_irq_restore(flags);
+#else
+		raw_spin_unlock_irqrestore(&logbuf_lock, flags);
+		call_console_drivers(_con_start, _log_end);
+#endif
 	}
 	console_locked = 0;
 
-- 
1.7.10.4