linux-kernel - [PATCH printk v4 16/39] printk: console_is_usable: use console_srcu_read

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Date:   Mon, 14 Nov 2022 17:35:09 +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 v4 16/39] printk: console_is_usable: use console_srcu_read_flags

All users of console_is_usable() are SRCU iterators. Use the
appropriate wrapper function to locklessly read the flags.

Signed-off-by: John Ogness <john.ogness@...utronix.de>
---
 kernel/printk/printk.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
index 3d9e5bb1a50b..bc563972e468 100644
--- a/kernel/printk/printk.c
+++ b/kernel/printk/printk.c
@@ -2708,11 +2708,13 @@ static bool abandon_console_lock_in_panic(void)
  * Check if the given console is currently capable and allowed to print
  * records.
  *
- * Requires the console_lock.
+ * Requires the console_srcu_read_lock.
  */
 static inline bool console_is_usable(struct console *con)
 {
-	if (!(con->flags & CON_ENABLED))
+	short flags = console_srcu_read_flags(con);
+
+	if (!(flags & CON_ENABLED))
 		return false;
 
 	if (!con->write)
@@ -2723,8 +2725,7 @@ static inline bool console_is_usable(struct console *con)
 	 * allocated. So unless they're explicitly marked as being able to
 	 * cope (CON_ANYTIME) don't call them until this CPU is officially up.
 	 */
-	if (!cpu_online(raw_smp_processor_id()) &&
-	    !(con->flags & CON_ANYTIME))
+	if (!cpu_online(raw_smp_processor_id()) && !(flags & CON_ANYTIME))
 		return false;
 
 	return true;
-- 
2.30.2