printk-rt-support.patch

From ea6f121070cca941ce652bd7f1a7777e181e0395 Mon Sep 17 00:00:00 2001
From: Ingo Molnar <mingo@elte.hu>
Date: Fri, 3 Jul 2009 08:30:19 -0500
Subject: [PATCH] printk: rt support

commit ba9d983171714db0483871cab172db4092f35699 in tip.

Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>

diff --git a/kernel/printk.c b/kernel/printk.c
index 45cf99a..2a07a18 100644
--- a/kernel/printk.c
+++ b/kernel/printk.c
@@ -36,6 +36,7 @@
 #include <linux/ratelimit.h>
 #include <linux/kmsg_dump.h>
 #include <linux/syslog.h>
+#include <linux/semaphore.h>
 
 #include <asm/uaccess.h>
 
@@ -423,7 +424,7 @@ static void __call_console_drivers(unsigned start, unsigned end)
 
 	for_each_console(con) {
 		if ((con->flags & CON_ENABLED) && con->write &&
-				(cpu_online(smp_processor_id()) ||
+				(cpu_online(raw_smp_processor_id()) ||
 				(con->flags & CON_ANYTIME)))
 			con->write(con, &LOG_BUF(start), end - start);
 	}
@@ -539,6 +540,7 @@ static void zap_locks(void)
 	raw_spin_lock_init(&logbuf_lock);
 	/* And make sure that we print immediately */
 	semaphore_init(&console_sem);
+	zap_rt_locks();
 }
 
 #if defined(CONFIG_PRINTK_TIME)
@@ -677,7 +679,7 @@ asmlinkage int vprintk(const char *fmt, va_list args)
 	preempt_disable();
 	/* This stops the holder of console_sem just where we want him */
 	raw_local_irq_save(flags);
-	this_cpu = smp_processor_id();
+	this_cpu = raw_smp_processor_id();
 
 	/*
 	 * Ouch, printk recursed into itself!
@@ -692,7 +694,7 @@ asmlinkage int vprintk(const char *fmt, va_list args)
 		 */
 		if (!oops_in_progress) {
 			recursion_bug = 1;
-			goto out_restore_irqs;
+			goto out;
 		}
 		zap_locks();
 	}
@@ -700,6 +702,7 @@ asmlinkage int vprintk(const char *fmt, va_list args)
 	lockdep_off();
 	raw_spin_lock(&logbuf_lock);
 	printk_cpu = this_cpu;
+	preempt_enable();
 
 	if (recursion_bug) {
 		recursion_bug = 0;
@@ -788,10 +791,8 @@ asmlinkage int vprintk(const char *fmt, va_list args)
 		release_console_sem();
 
 	lockdep_on();
-out_restore_irqs:
+out:
 	raw_local_irq_restore(flags);
-
-	preempt_enable();
 	return printed_len;
 }
 EXPORT_SYMBOL(printk);
@@ -1054,15 +1055,37 @@ void release_console_sem(void)
 		_con_start = con_start;
 		_log_end = log_end;
 		con_start = log_end;		/* Flush */
+
+		/*
+		 * on PREEMPT_RT, call console drivers with
+		 * interrupts enabled (if printk was called
+		 * with interrupts disabled):
+		 */
+#ifdef CONFIG_PREEMPT_RT
+		raw_spin_unlock_irqrestore(&logbuf_lock, flags);
+#else
 		raw_spin_unlock(&logbuf_lock);
 		stop_critical_timings();	/* don't trace print latency */
+#endif
 		call_console_drivers(_con_start, _log_end);
 		start_critical_timings();
+#ifndef CONFIG_PREEMPT_RT
 		local_irq_restore(flags);
+#endif
 	}
 	console_locked = 0;
-	up(&console_sem);
 	raw_spin_unlock_irqrestore(&logbuf_lock, flags);
+	up(&console_sem);
+
+	/*
+	 * On PREEMPT_RT kernels __wake_up may sleep, so wake syslogd
+	 * up only if we are in a preemptible section. We normally dont
+	 * printk from non-preemptible sections so this is for the emergency
+	 * case only.
+	 */
+#ifdef CONFIG_PREEMPT_RT
+	if (!in_atomic() && !irqs_disabled())
+#endif
 	if (wake_klogd)
 		wake_up_klogd();
 }
@@ -1401,6 +1424,21 @@ bool printk_timed_ratelimit(unsigned long *caller_jiffies,
 }
 EXPORT_SYMBOL(printk_timed_ratelimit);
 
+static DEFINE_RAW_SPINLOCK(warn_lock);
+
+void __WARN_ON(const char *func, const char *file, const int line)
+{
+	unsigned long flags;
+
+	raw_spin_lock_irqsave(&warn_lock, flags);
+	printk("%s/%d[CPU#%d]: BUG in %s at %s:%d\n",
+		current->comm, current->pid, raw_smp_processor_id(),
+		func, file, line);
+	dump_stack();
+	raw_spin_unlock_irqrestore(&warn_lock, flags);
+}
+EXPORT_SYMBOL(__WARN_ON);
+
 static DEFINE_SPINLOCK(dump_list_lock);
 static LIST_HEAD(dump_list);
 
-- 
1.7.1.1