Messages in this thread Patch in this message |  | | From | Feng Tang <> | Subject | [PATCH v3] panic: add an option to replay all the printk message in buffer | Date | Wed, 24 Apr 2019 16:51:12 +0800 |
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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 .
Signed-off-by: Feng Tang <feng.tang@intel.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> --- Changelog:
v3: - Solve the compile issue when CONFIG_PRINTK=n, found by Andrew Morton - Add enum for parameter of console_flush_on_panic() - move the printk replay code to console_flush_on_panic()
v2: - Add a new func in printk.c dedicated for the replaying, as suggested by Petr Mladek - Combine the 2 patches in v1 into one suggested by both Petr and Sergey
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(-)
diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt index 858b6c0..e56fe86 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -3104,6 +3104,7 @@ 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(). diff --git a/arch/powerpc/kernel/traps.c b/arch/powerpc/kernel/traps.c index 64936b6..852362c 100644 --- a/arch/powerpc/kernel/traps.c +++ b/arch/powerpc/kernel/traps.c @@ -178,7 +178,7 @@ 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) diff --git a/include/linux/console.h b/include/linux/console.h index ec9bdb3..d09951d 100644 --- a/include/linux/console.h +++ b/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 *); diff --git a/kernel/panic.c b/kernel/panic.c index b9f004e..b9c0eb3 100644 --- a/kernel/panic.c +++ b/kernel/panic.c @@ -53,6 +53,7 @@ int panic_suppress_printk; #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); @@ -136,6 +137,11 @@ 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(); @@ -279,8 +285,6 @@ 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) diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c index d460144..237191b 100644 --- a/kernel/printk/printk.c +++ b/kernel/printk/printk.c @@ -2485,10 +2485,11 @@ 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 @@ -2499,6 +2500,11 @@ 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(); } -- 2.7.4
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