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

MAINTAINERS

@@ -15396,6 +15396,7 @@ M:	Sergey Senozhatsky <senozhatsky@chromium.org>
 R:	Steven Rostedt <rostedt@goodmis.org>
 R:	John Ogness <john.ogness@linutronix.de>
 S:	Maintained
+T:	git git://git.kernel.org/pub/scm/linux/kernel/git/printk/linux.git
 F:	include/linux/printk.h
 F:	kernel/printk/
 
@@ -20525,7 +20526,7 @@ M:	Sergey Senozhatsky <senozhatsky@chromium.org>
 R:	Andy Shevchenko <andriy.shevchenko@linux.intel.com>
 R:	Rasmus Villemoes <linux@rasmusvillemoes.dk>
 S:	Maintained
-T:	git git://git.kernel.org/pub/scm/linux/kernel/git/pmladek/printk.git
+T:	git git://git.kernel.org/pub/scm/linux/kernel/git/printk/linux.git
 F:	Documentation/core-api/printk-formats.rst
 F:	lib/test_printf.c
 F:	lib/test_scanf.c

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);

lib/vsprintf.c

@@ -3564,7 +3564,7 @@ int vsscanf(const char *buf, const char *fmt, va_list args)
 				++fmt;
 
 			for ( ; *fmt && *fmt != ']'; ++fmt, ++len)
-				set_bit((u8)*fmt, set);
+				__set_bit((u8)*fmt, set);
 
 			/* no ']' or no character set found */
 			if (!*fmt || !len)
@@ -3574,7 +3574,7 @@ int vsscanf(const char *buf, const char *fmt, va_list args)
 			if (negate) {
 				bitmap_complement(set, set, 256);
 				/* exclude null '\0' byte */
-				clear_bit(0, set);
+				__clear_bit(0, set);
 			}
 
 			/* match must be non-empty */

scripts/gdb/linux/dmesg.py

@@ -44,19 +44,17 @@ class LxDmesg(gdb.Command):
         sz = prb_desc_ring_type.get_type().sizeof
         desc_ring = utils.read_memoryview(inf, addr, sz).tobytes()
 
-        # read in descriptor array
+        # read in descriptor count, size, and address
         off = prb_desc_ring_type.get_type()['count_bits'].bitpos // 8
         desc_ring_count = 1 << utils.read_u32(desc_ring, off)
         desc_sz = prb_desc_type.get_type().sizeof
         off = prb_desc_ring_type.get_type()['descs'].bitpos // 8
-        addr = utils.read_ulong(desc_ring, off)
-        descs = utils.read_memoryview(inf, addr, desc_sz * desc_ring_count).tobytes()
+        desc_addr = utils.read_ulong(desc_ring, off)
 
-        # read in info array
+        # read in info size and address
         info_sz = printk_info_type.get_type().sizeof
         off = prb_desc_ring_type.get_type()['infos'].bitpos // 8
-        addr = utils.read_ulong(desc_ring, off)
-        infos = utils.read_memoryview(inf, addr, info_sz * desc_ring_count).tobytes()
+        info_addr = utils.read_ulong(desc_ring, off)
 
         # read in text data ring structure
         off = printk_ringbuffer_type.get_type()['text_data_ring'].bitpos // 8
@@ -64,12 +62,11 @@ class LxDmesg(gdb.Command):
         sz = prb_data_ring_type.get_type().sizeof
         text_data_ring = utils.read_memoryview(inf, addr, sz).tobytes()
 
-        # read in text data
+        # read in text data size and address
         off = prb_data_ring_type.get_type()['size_bits'].bitpos // 8
         text_data_sz = 1 << utils.read_u32(text_data_ring, off)
         off = prb_data_ring_type.get_type()['data'].bitpos // 8
-        addr = utils.read_ulong(text_data_ring, off)
-        text_data = utils.read_memoryview(inf, addr, text_data_sz).tobytes()
+        text_data_addr = utils.read_ulong(text_data_ring, off)
 
         counter_off = atomic_long_type.get_type()['counter'].bitpos // 8
 
@@ -102,17 +99,20 @@ class LxDmesg(gdb.Command):
             desc_off = desc_sz * ind
             info_off = info_sz * ind
 
+            desc = utils.read_memoryview(inf, desc_addr + desc_off, desc_sz).tobytes()
+
             # skip non-committed record
-            state = 3 & (utils.read_u64(descs, desc_off + sv_off +
-                                        counter_off) >> desc_flags_shift)
+            state = 3 & (utils.read_u64(desc, sv_off + counter_off) >> desc_flags_shift)
             if state != desc_committed and state != desc_finalized:
                 if did == head_id:
                     break
                 did = (did + 1) & desc_id_mask
                 continue
 
-            begin = utils.read_ulong(descs, desc_off + begin_off) % text_data_sz
-            end = utils.read_ulong(descs, desc_off + next_off) % text_data_sz
+            begin = utils.read_ulong(desc, begin_off) % text_data_sz
+            end = utils.read_ulong(desc, next_off) % text_data_sz
+
+            info = utils.read_memoryview(inf, info_addr + info_off, info_sz).tobytes()
 
             # handle data-less record
             if begin & 1 == 1:
@@ -125,16 +125,17 @@ class LxDmesg(gdb.Command):
                 # skip over descriptor id
                 text_start = begin + utils.get_long_type().sizeof
 
-                text_len = utils.read_u16(infos, info_off + len_off)
+                text_len = utils.read_u16(info, len_off)
 
                 # handle truncated message
                 if end - text_start < text_len:
                     text_len = end - text_start
 
-                text = text_data[text_start:text_start + text_len].decode(
-                    encoding='utf8', errors='replace')
+                text_data = utils.read_memoryview(inf, text_data_addr + text_start,
+                                                  text_len).tobytes()
+                text = text_data[0:text_len].decode(encoding='utf8', errors='replace')
 
-            time_stamp = utils.read_u64(infos, info_off + ts_off)
+            time_stamp = utils.read_u64(info, ts_off)
 
             for line in text.splitlines():
                 msg = u"[{time:12.6f}] {line}\n".format(