linux-kernel - [PATCH printk v3 15/15] printk: remove @console

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Message-Id: <20220419234637.357112-16-john.ogness@linutronix.de>
Date:   Wed, 20 Apr 2022 01:52:37 +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 v3 15/15] printk: remove @console_locked

The static global variable @console_locked is used to help debug
VT code to make sure that certain code paths are running with
the console_lock held. However, this information is also available
with the static global variable @console_kthreads_blocked (for
locking via console_lock()), and the static global variable
@console_kthreads_active (for locking via console_trylock()).

Remove @console_locked and update is_console_locked() to use the
alternative variables.

Signed-off-by: John Ogness <john.ogness@...utronix.de>
Reviewed-by: Petr Mladek <pmladek@...e.com>
---
 kernel/printk/printk.c | 31 ++++++++++++++-----------------
 1 file changed, 14 insertions(+), 17 deletions(-)

diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
index 6d5f57142cd9..c9e0b0abbedd 100644
--- a/kernel/printk/printk.c
+++ b/kernel/printk/printk.c
@@ -340,15 +340,7 @@ static void console_kthreads_unblock(void)
 	console_kthreads_blocked = false;
 }
 
-/*
- * This is used for debugging the mess that is the VT code by
- * keeping track if we have the console semaphore held. It's
- * definitely not the perfect debug tool (we don't know if _WE_
- * hold it and are racing, but it helps tracking those weird code
- * paths in the console code where we end up in places I want
- * locked without the console semaphore held).
- */
-static int console_locked, console_suspended;
+static int console_suspended;
 
 /*
  *	Array of consoles built from command line options (console=)
@@ -2690,7 +2682,6 @@ void console_lock(void)
 	if (console_suspended)
 		return;
 	console_kthreads_block();
-	console_locked = 1;
 	console_may_schedule = 1;
 }
 EXPORT_SYMBOL(console_lock);
@@ -2705,13 +2696,11 @@ void console_lock_single_hold(struct console *con)
 	might_sleep();
 	down_console_sem();
 	mutex_lock(&con->lock);
-	console_locked = 1;
 	console_may_schedule = 1;
 }
 
 static void console_unlock_single_release(struct console *con)
 {
-	console_locked = 0;
 	mutex_unlock(&con->lock);
 	up_console_sem();
 }
@@ -2736,15 +2725,26 @@ int console_trylock(void)
 		up_console_sem();
 		return 0;
 	}
-	console_locked = 1;
 	console_may_schedule = 0;
 	return 1;
 }
 EXPORT_SYMBOL(console_trylock);
 
+/*
+ * This is used to help to make sure that certain paths within the VT code are
+ * running with the console lock held. It is definitely not the perfect debug
+ * tool (it is not known if the VT code is the task holding the console lock),
+ * but it helps tracking those weird code paths in the console code such as
+ * when the console is suspended: where the console is not locked but no
+ * console printing may occur.
+ *
+ * Note: This returns true when the console is suspended but is not locked.
+ *       This is intentional because the VT code must consider that situation
+ *       the same as if the console was locked.
+ */
 int is_console_locked(void)
 {
-	return (console_locked || atomic_read(&console_kthreads_active));
+	return (console_kthreads_blocked || atomic_read(&console_kthreads_active));
 }
 EXPORT_SYMBOL(is_console_locked);
 
@@ -2800,8 +2800,6 @@ static inline bool console_is_usable(struct console *con)
 
 static void __console_unlock(void)
 {
-	console_locked = 0;
-
 	/*
 	 * Depending on whether console_lock() or console_trylock() was used,
 	 * appropriately allow the kthread printers to continue.
@@ -3118,7 +3116,6 @@ void console_unblank(void)
 	} else
 		console_lock();
 
-	console_locked = 1;
 	console_may_schedule = 0;
 	for_each_console(c)
 		if ((c->flags & CON_ENABLED) && c->unblank)
-- 
2.30.2