linux-kernel - [PATCH printk v2 31/38] printk: register_console: use srcu console list iterator

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Message-Id: <20221019145600.1282823-32-john.ogness@linutronix.de>
Date:   Wed, 19 Oct 2022 17:01:53 +0206
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 v2 31/38] printk: register_console: use srcu console list iterator

Use srcu console list iteration for console list traversal. Now
the traversal at the beginning of register_console() is safe.

Signed-off-by: John Ogness <john.ogness@...utronix.de>
---
 kernel/printk/printk.c | 11 +++++++----
 1 file changed, 7 insertions(+), 4 deletions(-)

diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
index 410ad9d5649c..809c43e596d8 100644
--- a/kernel/printk/printk.c
+++ b/kernel/printk/printk.c
@@ -3188,20 +3188,23 @@ void register_console(struct console *newcon)
 	struct console *con;
 	bool bootcon_enabled = false;
 	bool realcon_enabled = false;
+	int cookie;
 	int err;
 
-	for_each_console(con) {
+	cookie = console_srcu_read_lock();
+	for_each_console_srcu(con) {
 		if (WARN(con == newcon, "console '%s%d' already registered\n",
-					 con->name, con->index))
+					 con->name, con->index)) {
+			console_srcu_read_unlock(cookie);
 			return;
-	}
+		}
 
-	for_each_console(con) {
 		if (con->flags & CON_BOOT)
 			bootcon_enabled = true;
 		else
 			realcon_enabled = true;
 	}
+	console_srcu_read_unlock(cookie);
 
 	/* Do not register boot consoles when there already is a real one. */
 	if (newcon->flags & CON_BOOT && realcon_enabled) {
-- 
2.30.2