linux-kernel - [PATCH 10/10] printk: Split console call from vprintk

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Message-Id: <1432557993-20458-11-git-send-email-pmladek@suse.cz>
Date:	Mon, 25 May 2015 14:46:33 +0200
From:	Petr Mladek <pmladek@...e.cz>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Frederic Weisbecker <fweisbec@...il.com>,
	Steven Rostedt <rostedt@...dmis.org>,
	Dave Anderson <anderson@...hat.com>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	Kay Sievers <kay@...y.org>, Jiri Kosina <jkosina@...e.cz>,
	Michal Hocko <mhocko@...e.cz>, Jan Kara <jack@...e.cz>,
	linux-kernel@...r.kernel.org, Wang Long <long.wanglong@...wei.com>,
	peifeiyue@...wei.com, dzickus@...hat.com, morgan.wang@...wei.com,
	sasha.levin@...cle.com, Petr Mladek <pmladek@...e.cz>
Subject: [PATCH 10/10] printk: Split console call from vprintk_emit()

vprintk_emit() is too long. Let's split the logic about when and how
to call the console into a separate function.

Well, it is not only about console but also about /dev/kmsg and syslog().
Hence the generic name vprintk_poke_loggers() seems to be more appropriate.

This patch just shuffles the code. There is no change in the functionality.

Signed-off-by: Petr Mladek <pmladek@...e.cz>
---
 kernel/printk/printk.c | 72 ++++++++++++++++++++++++++++----------------------
 1 file changed, 41 insertions(+), 31 deletions(-)

diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
index c0b97653987a..fb4af49c2d4e 100644
--- a/kernel/printk/printk.c
+++ b/kernel/printk/printk.c
@@ -1877,6 +1877,46 @@ static int vprintk_store_text(int facility, int level, enum log_flags lflags,
 	return printed_len;
 }
 
+/*
+ * Try to get console, wake up logging services, and flush the last
+ * messages there.
+ */
+static void vprintk_poke_loggers(bool in_sched)
+{
+	/*
+	 * If called from the scheduler or NMI context, we can not get console
+	 * without a possible deadlock. In this case, we must deffer the task
+	 * via IRQ work.
+	 *
+	 * The only exception are Oops messages from NMI context where all
+	 * relevant locks have been forcefully dropped in
+	 * try_logbuf_lock_in_nmi(). We have to try to get the console,
+	 * otherwise the last messages would get lost.
+	 */
+	if (in_sched || (in_nmi() && !oops_in_progress)) {
+		__this_cpu_or(printk_pending, PRINTK_PENDING_OUTPUT);
+		irq_work_queue(this_cpu_ptr(&wake_up_klogd_work));
+	} else {
+		lockdep_off();
+		/*
+		 * Disable preemption to avoid being preempted while holding
+		 * console_sem which would prevent anyone from printing to
+		 * console
+		 */
+		preempt_disable();
+
+		/*
+		 * Try to acquire and then immediately release the console
+		 * semaphore.  The release will print out buffers and wake up
+		 * /dev/kmsg and syslog() users.
+		 */
+		if (console_trylock_for_printk())
+			console_unlock();
+		preempt_enable();
+		lockdep_on();
+	}
+}
+
 asmlinkage int vprintk_emit(int facility, int level,
 			    const char *dict, size_t dictlen,
 			    const char *fmt, va_list args)
@@ -1952,37 +1992,7 @@ asmlinkage int vprintk_emit(int facility, int level,
 	lockdep_on();
 	local_irq_restore(flags);
 
-	/*
-	 * If called from the scheduler or NMI context, we can not get console
-	 * without a possible deadlock.
-	 *
-	 * The only exception are Oops messages from NMI context where all
-	 * relevant locks have been forcefully dropped in
-	 * try_logbuf_lock_in_nmi(). We have to try to get the console,
-	 * otherwise the last messages would get lost.
-	 */
-	if (in_sched || (in_nmi() && !oops_in_progress)) {
-		__this_cpu_or(printk_pending, PRINTK_PENDING_OUTPUT);
-		irq_work_queue(this_cpu_ptr(&wake_up_klogd_work));
-	} else {
-		lockdep_off();
-		/*
-		 * Disable preemption to avoid being preempted while holding
-		 * console_sem which would prevent anyone from printing to
-		 * console
-		 */
-		preempt_disable();
-
-		/*
-		 * Try to acquire and then immediately release the console
-		 * semaphore.  The release will print out buffers and wake up
-		 * /dev/kmsg and syslog() users.
-		 */
-		if (console_trylock_for_printk())
-			console_unlock();
-		preempt_enable();
-		lockdep_on();
-	}
+	vprintk_poke_loggers(in_sched);
 
 	return printed_len;
 }
-- 
1.8.5.6

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