linux-kernel - [ANNOUNCE] 4.14.87-rt49

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Message-ID: <20181218154034.612d729d@gandalf.local.home>
Date:   Tue, 18 Dec 2018 15:40:34 -0500
From:   Steven Rostedt <rostedt@...dmis.org>
To:     LKML <linux-kernel@...r.kernel.org>,
        linux-rt-users <linux-rt-users@...r.kernel.org>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Carsten Emde <C.Emde@...dl.org>,
        John Kacur <jkacur@...hat.com>,
        Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
        Julia Cartwright <julia@...com>,
        Daniel Wagner <daniel.wagner@...mens.com>,
        Tom Zanussi <tom.zanussi@...ux.intel.com>
Subject: [ANNOUNCE] 4.14.87-rt49


Dear RT Folks,

I'm pleased to announce the 4.14.87-rt49 stable release.

Sorry for taking so long, I've just been swamped (like everyone else)

*** PLEASE NOTE ***

This release is **NOT** just an update to the new stable 4.14.87 version
as there was a small RT specific change that has been made.

I had to make an update to handle a backport of adding
preempt_disable() around the console_unlock() code. That patch is below.

You can get this release via the git tree at:

  git://git.kernel.org/pub/scm/linux/kernel/git/rt/linux-stable-rt.git

  branch: v4.14-rt
  Head SHA1: c3fb62599cb0bf9ea0223433ccf7c0c37056c392


Or to build 4.14.87-rt49 directly, the following patches should be applied:

  http://www.kernel.org/pub/linux/kernel/v4.x/linux-4.14.tar.xz

  http://www.kernel.org/pub/linux/kernel/v4.x/patch-4.14.87.xz

  http://www.kernel.org/pub/linux/kernel/projects/rt/4.14/patch-4.14.87-rt49.patch.xz




Enjoy,

-- Steve


>From 0ab3459b0a8b8d19054aa813611c8dc22ce04af8 Mon Sep 17 00:00:00 2001
From: "Steven Rostedt (VMware)" <rostedt@...dmis.org>
Date: Fri, 14 Dec 2018 21:36:55 -0500
Subject: [PATCH] printk: Do not disable preemption when calling consoles in RT

console_unlock() may call consoles that call spin_lock(), where spin_lock is
a mutex in PREEMPT_RT. Although mainline may be worried about preempted
holders of the console lock from preventing printk() output, the RT kernel
does not.

Use migrate_disable() to disable preemption when !RT, but we really don't
care if the task stays on the CPU or not for RT. It just has to be able to
schedule.

Signed-off-by: Steven Rostedt (VMware) <rostedt@...dmis.org>
---
 kernel/printk/printk.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
index 8a7c4f79fca0..029ae3caa80e 100644
--- a/kernel/printk/printk.c
+++ b/kernel/printk/printk.c
@@ -1811,7 +1811,7 @@ asmlinkage int vprintk_emit(int facility, int level,
 		 * console_sem which would prevent anyone from printing to
 		 * console
 		 */
-		preempt_disable();
+		migrate_disable();
 		/*
 		 * Try to acquire and then immediately release the console
 		 * semaphore.  The release will print out buffers and wake up
@@ -1819,7 +1819,7 @@ asmlinkage int vprintk_emit(int facility, int level,
 		 */
 		if (may_trylock && console_trylock())
 			console_unlock();
-		preempt_enable();
+		migrate_enable();
 	}
 
 	return printed_len;
-- 
2.19.2