diff mbox series

[printk,v3,11/40] um: kmsg_dumper: use srcu console list iterator

Message ID 20221107141638.3790965-12-john.ogness@linutronix.de
State New
Headers
Series reduce console_lock scope |

Commit Message

John Ogness Nov. 7, 2022, 2:16 p.m. UTC 
  Rather than using the console_lock to guarantee safe console list
traversal, use srcu console list iteration.

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

Comments

Petr Mladek Nov. 9, 2022, 3:05 p.m. UTC | #1 
On Mon 2022-11-07 15:22:09, John Ogness wrote:
> Rather than using the console_lock to guarantee safe console list
> traversal, use srcu console list iteration.

It might be obvious. But I would add:

"It allows to dump the messages even when console_lock() is blocked
during panic()."

It will help to understand this is a clear win.

> Signed-off-by: John Ogness <john.ogness@linutronix.de>

After merging with 9th patch for using the racy console_is_enabled(con):

Reviewed-by: Petr Mladek <pmladek@suse.com>

Best Regards,
Petr
diff mbox series

Patch

diff --git a/arch/um/kernel/kmsg_dump.c b/arch/um/kernel/kmsg_dump.c
index f0233e2f8de0..b6acb3837f1d 100644
--- a/arch/um/kernel/kmsg_dump.c
+++ b/arch/um/kernel/kmsg_dump.c
@@ -16,16 +16,15 @@  static void kmsg_dumper_stdout(struct kmsg_dumper *dumper,
 	struct console *con;
 	unsigned long flags;
 	size_t len = 0;
+	int cookie;
 
 	/*
 	 * If no consoles are available to output crash information, dump
 	 * the kmsg buffer to stdout.
 	 */
 
-	if (!console_trylock())
-		return;
-
-	for_each_console(con) {
+	cookie = console_srcu_read_lock();
+	for_each_console_srcu(con) {
 		/*
 		 * The ttynull console and disabled consoles are ignored
 		 * since they cannot output. All other consoles are
@@ -36,9 +35,7 @@  static void kmsg_dumper_stdout(struct kmsg_dumper *dumper,
 			break;
 		}
 	}
-
-	console_unlock();
-
+	console_srcu_read_unlock(cookie);
 	if (con)
 		return;