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From: Jan Kara <jack@suse.cz>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: LKML <linux-kernel@vger.kernel.org>,
	pmladek@suse.cz, Steven Rostedt <rostedt@goodmis.org>,
	Frederic Weisbecker <fweisbec@gmail.com>, Jan Kara <jack@suse.cz>
Subject: [PATCH 1/6] printk: Remove outdated comment
Date: Thu, 13 Mar 2014 16:58:33 +0100	[thread overview]
Message-ID: <1394726318-2757-2-git-send-email-jack@suse.cz> (raw)
In-Reply-To: <1394726318-2757-1-git-send-email-jack@suse.cz>

Comment about interesting interlocking between lockbuf_lock and
console_sem is outdated. It was added in 2002 by commit
a880f45a48be2956d2c78a839c472287d54435c1 during conversion of
console_lock to console_sem + lockbuf_lock. At that time
release_console_sem() (today's equivalent is console_unlock()) was
indeed using lockbuf_lock to avoid races between trylock on console_sem
in printk() and unlock of console_sem. However these days the
interlocking is gone and the races are avoided by rechecking logbuf
state after releasing console_sem.

Signed-off-by: Jan Kara <jack@suse.cz>
---
 kernel/printk/printk.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
index 4dae9cbe9259..bd7ee2a9f960 100644
--- a/kernel/printk/printk.c
+++ b/kernel/printk/printk.c
@@ -206,8 +206,7 @@ struct printk_log {
 };
 
 /*
- * The logbuf_lock protects kmsg buffer, indices, counters. It is also
- * used in interesting ways to provide interlocking in console_unlock();
+ * The logbuf_lock protects kmsg buffer, indices, counters.
  */
 static DEFINE_RAW_SPINLOCK(logbuf_lock);
 
-- 
1.8.1.4


  reply	other threads:[~2014-03-13 15:58 UTC|newest]

Thread overview: 13+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2014-03-13 15:58 [PATCH 0/6 v2] printk: Cleanups and softlockup avoidance Jan Kara
2014-03-13 15:58 ` Jan Kara [this message]
2014-03-13 15:58 ` [PATCH 2/6] printk: Release lockbuf_lock before calling console_trylock_for_printk() Jan Kara
2014-03-13 15:58 ` [PATCH 3/6] printk: Enable interrupts " Jan Kara
2014-03-13 15:58 ` [PATCH 4/6] printk: Remove separate printk_sched buffers and use printk buf instead Jan Kara
2014-03-13 15:58 ` [PATCH 5/6] printk: Hand over printing to console if printing too long Jan Kara
2014-03-13 23:06   ` Andrew Morton
2014-03-13 23:26     ` One Thousand Gnomes
2014-03-14 12:26       ` Jan Kara
2014-03-14 13:00     ` Jan Kara
2014-03-14 13:30     ` Jan Kara
2014-03-13 15:58 ` [PATCH 6/6] kernel: Avoid softlockups in stop_machine() during heavy printing Jan Kara
2014-03-13 23:09   ` Andrew Morton

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