linux-kernel - [PATCH printk v3 08/40] printk: use console_is

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Date:   Mon,  7 Nov 2022 15:22:06 +0106
From:   John Ogness <john.ogness@...utronix.de>
To:     Petr Mladek <pmladek@...e.com>
Cc:     Sergey Senozhatsky <senozhatsky@...omium.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        linux-kernel@...r.kernel.org
Subject: [PATCH printk v3 08/40] printk: use console_is_enabled()

Replace (console->flags & CON_ENABLED) usage with console_is_enabled()
if it involves a data race. Otherwise add comments mentioning why the
wrapper is not used.

Note that this is a preparatory change for when console_lock no longer
provides synchronization for console->flags.

Signed-off-by: John Ogness <john.ogness@...utronix.de>
---
 kernel/printk/printk.c | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
index 79811984da34..f243bb56a3ba 100644
--- a/kernel/printk/printk.c
+++ b/kernel/printk/printk.c
@@ -2660,7 +2660,7 @@ static bool abandon_console_lock_in_panic(void)
  */
 static inline bool console_is_usable(struct console *con)
 {
-	if (!(con->flags & CON_ENABLED))
+	if (!console_is_enabled(con))
 		return false;
 
 	if (!con->write)
@@ -2946,7 +2946,7 @@ void console_unblank(void)
 	console_locked = 1;
 	console_may_schedule = 0;
 	for_each_console(c)
-		if ((c->flags & CON_ENABLED) && c->unblank)
+		if (console_is_enabled(c) && c->unblank)
 			c->unblank();
 	console_unlock();
 
@@ -3104,8 +3104,11 @@ static int try_enable_preferred_console(struct console *newcon,
 	 * Some consoles, such as pstore and netconsole, can be enabled even
 	 * without matching. Accept the pre-enabled consoles only when match()
 	 * and setup() had a chance to be called.
+	 *
+	 * Note that reading @flags is race-free because the console is not
+	 * yet added to the console list.
 	 */
-	if (newcon->flags & CON_ENABLED && c->user_specified ==	user_specified)
+	if ((newcon->flags & CON_ENABLED) && (c->user_specified == user_specified))
 		return 0;
 
 	return -ENOENT;
-- 
2.30.2