The patch titled
Subject: panic: add an option to replay all the printk message in buffer
has been added to the -mm tree. Its filename is
panic-add-an-option-to-replay-all-the-printk-message-in-buffer.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/panic-add-an-option-to-replay-all-the-printk-message-in-buffer.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/panic-add-an-option-to-replay-all-the-printk-message-in-buffer.patch
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*** Remember to use Documentation/process/submit-checklist.rst when testing your code ***
The -mm tree is included into linux-next and is updated
there every 3-4 working days
------------------------------------------------------
From: Feng Tang <feng.tang@xxxxxxxxx>
Subject: 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 .
Link: http://lkml.kernel.org/r/1556095872-36838-1-git-send-email-feng.tang@xxxxxxxxx
Signed-off-by: Feng Tang <feng.tang@xxxxxxxxx>
Cc: Aaro Koskinen <aaro.koskinen@xxxxxxxxx>
Cc: Petr Mladek <pmladek@xxxxxxxx>
Cc: Steven Rostedt <rostedt@xxxxxxxxxxx>
Cc: Sergey Senozhatsky <sergey.senozhatsky.work@xxxxxxxxx>
Cc: Kees Cook <keescook@xxxxxxxxxxxx>
Cc: Borislav Petkov <bp@xxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
Documentation/admin-guide/kernel-parameters.txt | 1 +
arch/powerpc/kernel/traps.c | 2 +-
include/linux/console.h | 7 ++++++-
kernel/panic.c | 8 ++++++--
kernel/printk/printk.c | 8 +++++++-
5 files changed, 21 insertions(+), 5 deletions(-)
--- a/arch/powerpc/kernel/traps.c~panic-add-an-option-to-replay-all-the-printk-message-in-buffer
+++ a/arch/powerpc/kernel/traps.c
@@ -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)
--- a/Documentation/admin-guide/kernel-parameters.txt~panic-add-an-option-to-replay-all-the-printk-message-in-buffer
+++ a/Documentation/admin-guide/kernel-parameters.txt
@@ -3145,6 +3145,7 @@
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().
--- a/include/linux/console.h~panic-add-an-option-to-replay-all-the-printk-message-in-buffer
+++ a/include/linux/console.h
@@ -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 *);
--- a/kernel/panic.c~panic-add-an-option-to-replay-all-the-printk-message-in-buffer
+++ a/kernel/panic.c
@@ -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 +135,11 @@ 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);
+ else
+ console_flush_on_panic(CONSOLE_FLUSH_PENDING);
+
if (panic_print & PANIC_PRINT_TASK_INFO)
show_state();
@@ -277,8 +283,6 @@ void panic(const char *fmt, ...)
* panic() is not being callled from OOPS.
*/
debug_locks_off();
- console_flush_on_panic();
-
panic_print_sys_info();
if (!panic_blink)
--- a/kernel/printk/printk.c~panic-add-an-option-to-replay-all-the-printk-message-in-buffer
+++ a/kernel/printk/printk.c
@@ -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 +2550,11 @@ void console_flush_on_panic(void)
*/
console_trylock();
console_may_schedule = 0;
+
+ if (mode == CONSOLE_REPLAY_ALL) {
+ console_seq = log_first_seq;
+ console_idx = log_first_idx;
+ }
console_unlock();
}
_
Patches currently in -mm which might be from feng.tang@xxxxxxxxx are
panic-avoid-the-extra-noise-dmesg.patch
panic-add-an-option-to-replay-all-the-printk-message-in-buffer.patch
