Commit de6da1e8 authored by Feng Tang's avatar Feng Tang Committed by Linus Torvalds
Browse files

panic: add an option to replay all the printk message in buffer 

Currently on panic, kernel will lower the loglevel and print out pending
printk msg only with console_flush_on_panic().

Add an option for users to configure the "panic_print" to replay all
dmesg in buffer, some of which they may have never seen due to the
loglevel setting, which will help panic debugging .

[feng.tang@intel.com: keep the original console_flush_on_panic() inside panic()]
  Link: http://lkml.kernel.org/r/1556199137-14163-1-git-send-email-feng.tang@intel.com
[feng.tang@intel.com: use logbuf lock to protect the console log index]
  Link: http://lkml.kernel.org/r/1556269868-22654-1-git-send-email-feng.tang@intel.com
Link: http://lkml.kernel.org/r/1556095872-36838-1-git-send-email-feng.tang@intel.com


Signed-off-by: default avatarFeng Tang <feng.tang@intel.com>
Reviewed-by: default avatarPetr Mladek <pmladek@suse.com>
Cc: Aaro Koskinen <aaro.koskinen@nokia.com>
Cc: Petr Mladek <pmladek@suse.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Borislav Petkov <bp@suse.de>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 5d59aa8f

Documentation/admin-guide/kernel-parameters.txt

+1 −0
Original line number Diff line number Diff line
@@ -3212,6 +3212,7 @@ 
			bit 2: print timer info

			bit 3: print locks info if CONFIG_LOCKDEP is on

			bit 4: print ftrace buffer

			bit 5: print all printk messages in buffer



	panic_on_warn	panic() instead of WARN().  Useful to cause kdump

			on a WARN().

arch/powerpc/kernel/traps.c

+1 −1
Original line number Diff line number Diff line
@@ -179,7 +179,7 @@ extern void panic_flush_kmsg_end(void) 
	kmsg_dump(KMSG_DUMP_PANIC);

	bust_spinlocks(0);

	debug_locks_off();

	console_flush_on_panic();

	console_flush_on_panic(CONSOLE_FLUSH_PENDING);

}



static unsigned long oops_begin(struct pt_regs *regs)

include/linux/console.h

+6 −1
Original line number Diff line number Diff line
@@ -166,6 +166,11 @@ struct console { 
extern int console_set_on_cmdline;

extern struct console *early_console;



enum con_flush_mode {

	CONSOLE_FLUSH_PENDING,

	CONSOLE_REPLAY_ALL,

};



extern int add_preferred_console(char *name, int idx, char *options);

extern void register_console(struct console *);

extern int unregister_console(struct console *);
@@ -175,7 +180,7 @@ extern int console_trylock(void); 
extern void console_unlock(void);

extern void console_conditional_schedule(void);

extern void console_unblank(void);

extern void console_flush_on_panic(void);

extern void console_flush_on_panic(enum con_flush_mode mode);

extern struct tty_driver *console_device(int *);

extern void console_stop(struct console *);

extern void console_start(struct console *);

kernel/panic.c

+5 −1
Original line number Diff line number Diff line
@@ -51,6 +51,7 @@ EXPORT_SYMBOL_GPL(panic_timeout); 
#define PANIC_PRINT_TIMER_INFO		0x00000004

#define PANIC_PRINT_LOCK_INFO		0x00000008

#define PANIC_PRINT_FTRACE_INFO		0x00000010

#define PANIC_PRINT_ALL_PRINTK_MSG	0x00000020

unsigned long panic_print;



ATOMIC_NOTIFIER_HEAD(panic_notifier_list);
@@ -134,6 +135,9 @@ EXPORT_SYMBOL(nmi_panic); 


static void panic_print_sys_info(void)

{

	if (panic_print & PANIC_PRINT_ALL_PRINTK_MSG)

		console_flush_on_panic(CONSOLE_REPLAY_ALL);



	if (panic_print & PANIC_PRINT_TASK_INFO)

		show_state();
@@ -277,7 +281,7 @@ void panic(const char *fmt, ...) 
	 * panic() is not being callled from OOPS.

	 */

	debug_locks_off();

	console_flush_on_panic();

	console_flush_on_panic(CONSOLE_FLUSH_PENDING);



	panic_print_sys_info();

kernel/printk/printk.c

+11 −1
Original line number Diff line number Diff line
@@ -2535,10 +2535,11 @@ void console_unblank(void) 


/**

 * console_flush_on_panic - flush console content on panic

 * @mode: flush all messages in buffer or just the pending ones

 *

 * Immediately output all pending messages no matter what.

 */

void console_flush_on_panic(void)

void console_flush_on_panic(enum con_flush_mode mode)

{

	/*

	 * If someone else is holding the console lock, trylock will fail
@@ -2549,6 +2550,15 @@ void console_flush_on_panic(void) 
	 */

	console_trylock();

	console_may_schedule = 0;



	if (mode == CONSOLE_REPLAY_ALL) {

		unsigned long flags;



		logbuf_lock_irqsave(flags);

		console_seq = log_first_seq;

		console_idx = log_first_idx;

		logbuf_unlock_irqrestore(flags);

	}

	console_unlock();

}

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