linux-kernel - [PATCH printk v1 03/13] printk: use percpu flag instead of cpu

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 for Android: free password hash cracker in your pocket

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

Message-Id: <20220207194323.273637-4-john.ogness@linutronix.de>
Date:   Mon,  7 Feb 2022 20:49:13 +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,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: [PATCH printk v1 03/13] printk: use percpu flag instead of cpu_online()

The CON_ANYTIME console flag is used to label consoles that will
work correctly before percpu resources are allocated. To check
the condition, cpu_online(raw_smp_processor_id()) was used.
However, this is odd because CPUs can go offline at a later point.
Also, the function is forced to use the raw_ variant because
migration is not disabled.

Since commit ab6f762f0f53 ("printk: queue wake_up_klogd irq_work
only if per-CPU areas are ready") there is a variable to identify
if percpu resources have been allocated. Use that variable instead
of cpu_online(raw_smp_processor_id()).

Signed-off-by: John Ogness <john.ogness@...utronix.de>
---
 include/linux/console.h | 2 +-
 kernel/printk/printk.c  | 4 ++--
 2 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/include/linux/console.h b/include/linux/console.h
index 7cd758a4f44e..aa4d3fb4c1c5 100644
--- a/include/linux/console.h
+++ b/include/linux/console.h
@@ -133,7 +133,7 @@ static inline int con_debug_leave(void)
 #define CON_CONSDEV	(2) /* Preferred console, /dev/console */
 #define CON_ENABLED	(4)
 #define CON_BOOT	(8)
-#define CON_ANYTIME	(16) /* Safe to call when cpu is offline */
+#define CON_ANYTIME	(16) /* Safe to call before per-cpu resources ready */
 #define CON_BRL		(32) /* Used for a braille device */
 #define CON_EXTENDED	(64) /* Use the extended output format a la /dev/kmsg */
 
diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
index d1b773823d63..b346e60e9e51 100644
--- a/kernel/printk/printk.c
+++ b/kernel/printk/printk.c
@@ -2577,11 +2577,11 @@ static int have_callable_console(void)
  *
  * Console drivers may assume that per-cpu resources have been allocated. So
  * unless they're explicitly marked as being able to cope (CON_ANYTIME) don't
- * call them until this CPU is officially up.
+ * call them until per-cpu resources have been allocated.
  */
 static inline int can_use_console(void)
 {
-	return cpu_online(raw_smp_processor_id()) || have_callable_console();
+	return (printk_percpu_data_ready() || have_callable_console());
 }
 
 /**
-- 
2.30.2