linux-kernel - [PATCH v2 2/3] printk: console_flush_one

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-Id: <20250927-printk_legacy_thread_console_lock-v2-2-cff9f063071a@thegoodpenguin.co.uk>
Date: Sat, 27 Sep 2025 23:05:36 +0100
From: Andrew Murray <amurray@...goodpenguin.co.uk>
To: Petr Mladek <pmladek@...e.com>, Steven Rostedt <rostedt@...dmis.org>, 
 John Ogness <john.ogness@...utronix.de>, 
 Sergey Senozhatsky <senozhatsky@...omium.org>
Cc: linux-kernel@...r.kernel.org, 
 Andrew Murray <amurray@...goodpenguin.co.uk>
Subject: [PATCH v2 2/3] printk: console_flush_one_record() code cleanup

From: Petr Mladek <pmladek@...e.com>

console_flush_one_record() and console_flush_all() duplicate several
checks. They both want to tell the caller that consoles are not
longer usable in this context because it has lost the lock or
the lock has to be reserved for the panic CPU.

Pass this information by clearing the @any_usable parameter value
which has the same effect.

Reviewed-by: Andrew Murray <amurray@...goodpenguin.co.uk>
Signed-off-by: Petr Mladek <pmladek@...e.com>
---
 kernel/printk/printk.c | 23 +++++++++++------------
 1 file changed, 11 insertions(+), 12 deletions(-)

diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
index 060d4919de320fe21fd7aca73ba497e27c4ff334..e2c1cacdb4164489c60fe38f1e2837eb838107d6 100644
--- a/kernel/printk/printk.c
+++ b/kernel/printk/printk.c
@@ -3175,7 +3175,8 @@ static inline void printk_kthreads_check_locked(void) { }
  * console_lock, in which case the caller is no longer holding the
  * console_lock. Otherwise it is set to false.
  *
- * @any_usable will be set to true if there are any usable consoles.
+ * @any_usable will be set to true if there are any usable consoles
+ * in this context.
  *
  * Returns true when there was at least one usable console and a record was
  * flushed. A returned false indicates there were no records to flush for any
@@ -3193,6 +3194,7 @@ static bool console_flush_one_record(bool do_cond_resched, u64 *next_seq, bool *
 	bool any_progress;
 	int cookie;
 
+	*any_usable = false;
 	any_progress = false;
 
 	printk_get_console_flush_type(&ft);
@@ -3229,7 +3231,7 @@ static bool console_flush_one_record(bool do_cond_resched, u64 *next_seq, bool *
 		 * is already released.
 		 */
 		if (*handover)
-			return false;
+			goto unusable;
 
 		/* Track the next of the highest seq flushed. */
 		if (printk_seq > *next_seq)
@@ -3241,7 +3243,7 @@ static bool console_flush_one_record(bool do_cond_resched, u64 *next_seq, bool *
 
 		/* Allow panic_cpu to take over the consoles safely. */
 		if (other_cpu_in_panic())
-			goto abandon;
+			goto unusable_srcu;
 
 		if (do_cond_resched)
 			cond_resched();
@@ -3250,8 +3252,10 @@ static bool console_flush_one_record(bool do_cond_resched, u64 *next_seq, bool *
 
 	return any_progress;
 
-abandon:
+unusable_srcu:
 	console_srcu_read_unlock(cookie);
+unusable:
+	*any_usable = false;
 	return false;
 }
 
@@ -3280,21 +3284,16 @@ static bool console_flush_one_record(bool do_cond_resched, u64 *next_seq, bool *
  */
 static bool console_flush_all(bool do_cond_resched, u64 *next_seq, bool *handover)
 {
-	bool any_usable = false;
+	bool any_usable;
 	bool any_progress;
 
 	*next_seq = 0;
 	*handover = false;
 
 	do {
-		any_progress = console_flush_one_record(do_cond_resched, next_seq, handover,
-							&any_usable);
+		any_progress = console_flush_one_record(do_cond_resched, next_seq,
+							handover, &any_usable);
 
-		if (*handover)
-			return false;
-
-		if (other_cpu_in_panic())
-			return false;
 	} while (any_progress);
 
 	return any_usable;

-- 
2.34.1