Commit 9c35baf6 authored by Linus Torvalds's avatar Linus Torvalds
Browse files

Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/pmladek/printk 

Pull printk updates from Petr Mladek:

 - There is a situation when early console is not deregistered because
   the preferred one matches a wrong entry. It caused messages to appear
   twice.

   This is the 2nd attempt to fix it. The first one was wrong, see the
   commit c6c7d83b ('Revert "console: don't prefer first registered
   if DT specifies stdout-path"').

   The fix is coupled with some small code clean up. Well, the console
   registration code would deserve a big one. We need to think about it.

 - Do not lose information about the preemtive context when the console
   semaphore is re-taken.

 - Do not block CPU hotplug when someone else is already pushing
   messages to the console.

* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/pmladek/printk:
  printk: fix double printing with earlycon
  printk: rename selected_console -> preferred_console
  printk: fix name/type/scope of preferred_console var
  printk: Correctly handle preemption in console_unlock()
  printk: use console_trylock() in console_cpu_notify()
parents dd23f273 cf39bf58

kernel/printk/printk.c

+56 −25
Original line number Diff line number Diff line
@@ -269,8 +269,8 @@ static struct console *exclusive_console; 
#define MAX_CMDLINECONSOLES 8



static struct console_cmdline console_cmdline[MAX_CMDLINECONSOLES];

static int console_cmdline_cnt;



static int selected_console = -1;

static int preferred_console = -1;

int console_set_on_cmdline;

EXPORT_SYMBOL(console_set_on_cmdline);
@@ -1906,24 +1906,38 @@ static int __add_preferred_console(char *name, int idx, char *options, 
	 *	See if this tty is not yet registered, and

	 *	if we have a slot free.

	 */

	for (i = 0, c = console_cmdline;

	     i < MAX_CMDLINECONSOLES && c->name[0];

	     i++, c++) {

	for (i = 0, c = console_cmdline; i < console_cmdline_cnt; i++, c++) {

		if (strcmp(c->name, name) == 0 && c->index == idx) {

			if (!brl_options)

				selected_console = i;

			if (brl_options)

				return 0;



			/*

			 * Maintain an invariant that will help to find if

			 * the matching console is preferred, see

			 * register_console():

			 *

			 * The last non-braille console is always

			 * the preferred one.

			 */

			if (i != console_cmdline_cnt - 1)

				swap(console_cmdline[i],

				     console_cmdline[console_cmdline_cnt - 1]);



			preferred_console = console_cmdline_cnt - 1;



			return 0;

		}

	}

	if (i == MAX_CMDLINECONSOLES)

		return -E2BIG;

	if (!brl_options)

		selected_console = i;

		preferred_console = i;

	strlcpy(c->name, name, sizeof(c->name));

	c->options = options;

	braille_set_options(c, brl_options);



	c->index = idx;

	console_cmdline_cnt++;

	return 0;

}

/*
@@ -2031,14 +2045,15 @@ void resume_console(void) 
 * @cpu: unused

 *

 * If printk() is called from a CPU that is not online yet, the messages

 * will be spooled but will not show up on the console.  This function is

 * called when a new CPU comes online (or fails to come up), and ensures

 * that any such output gets printed.

 * will be printed on the console only if there are CON_ANYTIME consoles.

 * This function is called when a new CPU comes online (or fails to come

 * up) or goes offline.

 */

static int console_cpu_notify(unsigned int cpu)

{

	if (!cpuhp_tasks_frozen) {

		console_lock();

		/* If trylock fails, someone else is doing the printing */

		if (console_trylock())

			console_unlock();

	}

	return 0;
@@ -2161,7 +2176,7 @@ void console_unlock(void) 
	}



	/*

	 * Console drivers are called under logbuf_lock, so

	 * Console drivers are called with interrupts disabled, so

	 * @console_may_schedule should be cleared before; however, we may

	 * end up dumping a lot of lines, for example, if called from

	 * console registration path, and should invoke cond_resched()
@@ -2169,11 +2184,15 @@ void console_unlock(void) 
	 * scheduling stall on a slow console leading to RCU stall and

	 * softlockup warnings which exacerbate the issue with more

	 * messages practically incapacitating the system.

	 *

	 * console_trylock() is not able to detect the preemptive

	 * context reliably. Therefore the value must be stored before

	 * and cleared after the the "again" goto label.

	 */

	do_cond_resched = console_may_schedule;

again:

	console_may_schedule = 0;



again:

	/*

	 * We released the console_sem lock, so we need to recheck if

	 * cpu is online and (if not) is there at least one CON_ANYTIME
@@ -2409,6 +2428,7 @@ void register_console(struct console *newcon) 
	unsigned long flags;

	struct console *bcon = NULL;

	struct console_cmdline *c;

	static bool has_preferred;



	if (console_drivers)

		for_each_console(bcon)
@@ -2435,15 +2455,15 @@ void register_console(struct console *newcon) 
	if (console_drivers && console_drivers->flags & CON_BOOT)

		bcon = console_drivers;



	if (preferred_console < 0 || bcon || !console_drivers)

		preferred_console = selected_console;

	if (!has_preferred || bcon || !console_drivers)

		has_preferred = preferred_console >= 0;



	/*

	 *	See if we want to use this console driver. If we

	 *	didn't select a console we take the first one

	 *	that registers here.

	 */

	if (preferred_console < 0) {

	if (!has_preferred) {

		if (newcon->index < 0)

			newcon->index = 0;

		if (newcon->setup == NULL ||
@@ -2451,18 +2471,29 @@ void register_console(struct console *newcon) 
			newcon->flags |= CON_ENABLED;

			if (newcon->device) {

				newcon->flags |= CON_CONSDEV;

				preferred_console = 0;

				has_preferred = true;

			}

		}

	}



	/*

	 *	See if this console matches one we selected on

	 *	the command line.

	 * See if this console matches one we selected on the command line.

	 *

	 * There may be several entries in the console_cmdline array matching

	 * with the same console, one with newcon->match(), another by

	 * name/index:

	 *

	 *	pl011,mmio,0x87e024000000,115200 -- added from SPCR

	 *	ttyAMA0 -- added from command line

	 *

	 * Traverse the console_cmdline array in reverse order to be

	 * sure that if this console is preferred then it will be the first

	 * matching entry.  We use the invariant that is maintained in

	 * __add_preferred_console().

	 */

	for (i = 0, c = console_cmdline;

	     i < MAX_CMDLINECONSOLES && c->name[0];

	     i++, c++) {

	for (i = console_cmdline_cnt - 1; i >= 0; i--) {

		c = console_cmdline + i;



		if (!newcon->match ||

		    newcon->match(newcon, c->name, c->index, c->options) != 0) {

			/* default matching */
@@ -2484,9 +2515,9 @@ void register_console(struct console *newcon) 
		}



		newcon->flags |= CON_ENABLED;

		if (i == selected_console) {

		if (i == preferred_console) {

			newcon->flags |= CON_CONSDEV;

			preferred_console = selected_console;

			has_preferred = true;

		}

		break;

	}

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