Merge tag 'printk-for-5.17' of git://git.kernel.org/pub/scm/linux/kernel/git/printk/linux

Pull printk updates from Petr Mladek:

 - Remove some twists in the console registration code. It does not
   change the existing behavior except for one corner case. The proper
   default console (with tty binding) will be registered again even when
   it has been removed in the meantime. It is actually a bug fix.
   Anyway, this modified behavior requires some manual interaction.

 - Optimize gdb extension for huge ring buffers.

 - Do not use atomic operations for a local bitmap variable.

 - Update git links in MAINTAINERS.

* tag 'printk-for-5.17' of git://git.kernel.org/pub/scm/linux/kernel/git/printk/linux:
  MAINTAIERS/printk: Add link to printk git
  MAINTAINERS/vsprintf: Update link to printk git tree
  scripts/gdb: lx-dmesg: read records individually
  printk/console: Clean up boot console handling in register_console()
  printk/console: Remove need_default_console variable
  printk/console: Remove unnecessary need_default_console manipulation
  printk/console: Rename has_preferred_console to need_default_console
  printk/console: Split out code that enables default console
  vsprintf: Use non-atomic bitmap API when applicable

1 files changed, 58 insertions, 46 deletions

diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
index 57b132b658e1..155229f0cf0f 100644
--- a/kernel/printk/printk.c
+++ b/kernel/printk/printk.c
@@ -280,7 +280,6 @@ static struct console *exclusive_console;
 static struct console_cmdline console_cmdline[MAX_CMDLINECONSOLES];
 
 static int preferred_console = -1;
-static bool has_preferred_console;
 int console_set_on_cmdline;
 EXPORT_SYMBOL(console_set_on_cmdline);
 
@@ -2861,7 +2860,8 @@ early_param("keep_bootcon", keep_bootcon_setup);
  * Care need to be taken with consoles that are statically
  * enabled such as netconsole
  */
-static int try_enable_new_console(struct console *newcon, bool user_specified)
+static int try_enable_preferred_console(struct console *newcon,
+					bool user_specified)
 {
 	struct console_cmdline *c;
 	int i, err;
@@ -2891,10 +2891,8 @@ static int try_enable_new_console(struct console *newcon, bool user_specified)
 				return err;
 		}
 		newcon->flags |= CON_ENABLED;
-		if (i == preferred_console) {
+		if (i == preferred_console)
 			newcon->flags |= CON_CONSDEV;
-			has_preferred_console = true;
-		}
 		return 0;
 	}
 
@@ -2909,6 +2907,21 @@ static int try_enable_new_console(struct console *newcon, bool user_specified)
 	return -ENOENT;
 }
 
+/* Try to enable the console unconditionally */
+static void try_enable_default_console(struct console *newcon)
+{
+	if (newcon->index < 0)
+		newcon->index = 0;
+
+	if (newcon->setup && newcon->setup(newcon, NULL) != 0)
+		return;
+
+	newcon->flags |= CON_ENABLED;
+
+	if (newcon->device)
+		newcon->flags |= CON_CONSDEV;
+}
+
 /*
  * The console driver calls this routine during kernel initialization
  * to register the console printing procedure with printk() and to
@@ -2930,59 +2943,56 @@ static int try_enable_new_console(struct console *newcon, bool user_specified)
  */
 void register_console(struct console *newcon)
 {
-	struct console *bcon = NULL;
+	struct console *con;
+	bool bootcon_enabled = false;
+	bool realcon_enabled = false;
 	int err;
 
-	for_each_console(bcon) {
-		if (WARN(bcon == newcon, "console '%s%d' already registered\n",
-					 bcon->name, bcon->index))
+	for_each_console(con) {
+		if (WARN(con == newcon, "console '%s%d' already registered\n",
+					 con->name, con->index))
 			return;
 	}
 
-	/*
-	 * before we register a new CON_BOOT console, make sure we don't
-	 * already have a valid console
-	 */
-	if (newcon->flags & CON_BOOT) {
-		for_each_console(bcon) {
-			if (!(bcon->flags & CON_BOOT)) {
-				pr_info("Too late to register bootconsole %s%d\n",
-					newcon->name, newcon->index);
-				return;
-			}
-		}
+	for_each_console(con) {
+		if (con->flags & CON_BOOT)
+			bootcon_enabled = true;
+		else
+			realcon_enabled = true;
 	}
 
-	if (console_drivers && console_drivers->flags & CON_BOOT)
-		bcon = console_drivers;
-
-	if (!has_preferred_console || bcon || !console_drivers)
-		has_preferred_console = preferred_console >= 0;
+	/* Do not register boot consoles when there already is a real one. */
+	if (newcon->flags & CON_BOOT && realcon_enabled) {
+		pr_info("Too late to register bootconsole %s%d\n",
+			newcon->name, newcon->index);
+		return;
+	}
 
 	/*
-	 *	See if we want to use this console driver. If we
-	 *	didn't select a console we take the first one
-	 *	that registers here.
+	 * See if we want to enable this console driver by default.
+	 *
+	 * Nope when a console is preferred by the command line, device
+	 * tree, or SPCR.
+	 *
+	 * The first real console with tty binding (driver) wins. More
+	 * consoles might get enabled before the right one is found.
+	 *
+	 * Note that a console with tty binding will have CON_CONSDEV
+	 * flag set and will be first in the list.
 	 */
-	if (!has_preferred_console) {
-		if (newcon->index < 0)
-			newcon->index = 0;
-		if (newcon->setup == NULL ||
-		    newcon->setup(newcon, NULL) == 0) {
-			newcon->flags |= CON_ENABLED;
-			if (newcon->device) {
-				newcon->flags |= CON_CONSDEV;
-				has_preferred_console = true;
-			}
+	if (preferred_console < 0) {
+		if (!console_drivers || !console_drivers->device ||
+		    console_drivers->flags & CON_BOOT) {
+			try_enable_default_console(newcon);
 		}
 	}
 
 	/* See if this console matches one we selected on the command line */
-	err = try_enable_new_console(newcon, true);
+	err = try_enable_preferred_console(newcon, true);
 
 	/* If not, try to match against the platform default(s) */
 	if (err == -ENOENT)
-		err = try_enable_new_console(newcon, false);
+		err = try_enable_preferred_console(newcon, false);
 
 	/* printk() messages are not printed to the Braille console. */
 	if (err || newcon->flags & CON_BRL)
@@ -2994,8 +3004,10 @@ void register_console(struct console *newcon)
 	 * the real console are the same physical device, it's annoying to
 	 * see the beginning boot messages twice
 	 */
-	if (bcon && ((newcon->flags & (CON_CONSDEV | CON_BOOT)) == CON_CONSDEV))
+	if (bootcon_enabled &&
+	    ((newcon->flags & (CON_CONSDEV | CON_BOOT)) == CON_CONSDEV)) {
 		newcon->flags &= ~CON_PRINTBUFFER;
+	}
 
 	/*
 	 *	Put this console in the list - keep the
@@ -3051,15 +3063,15 @@ void register_console(struct console *newcon)
 	pr_info("%sconsole [%s%d] enabled\n",
 		(newcon->flags & CON_BOOT) ? "boot" : "" ,
 		newcon->name, newcon->index);
-	if (bcon &&
+	if (bootcon_enabled &&
 	    ((newcon->flags & (CON_CONSDEV | CON_BOOT)) == CON_CONSDEV) &&
 	    !keep_bootcon) {
 		/* We need to iterate through all boot consoles, to make
 		 * sure we print everything out, before we unregister them.
 		 */
-		for_each_console(bcon)
-			if (bcon->flags & CON_BOOT)
-				unregister_console(bcon);
+		for_each_console(con)
+			if (con->flags & CON_BOOT)
+				unregister_console(con);
 	}
 }
 EXPORT_SYMBOL(register_console);