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

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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: Feng Tang <feng.tang@intel.com>
Reviewed-by: Petr 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: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Feng Tang 2019-05-17 14:31:50 -07:00 committed by Linus Torvalds
parent 5d59aa8f9c
commit de6da1e8bc
5 changed files with 24 additions and 4 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

1
Documentation/admin-guide/kernel-parameters.txt
View File

@ -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().

2
arch/powerpc/kernel/traps.c
View File

@ -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)

7
include/linux/console.h
View File

@ -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 *);

6
kernel/panic.c
View File

@ -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();

12
kernel/printk/printk.c
View File

@ -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();
}