From f953f140f318a641c443b0b8c618155ed90a7a10 Mon Sep 17 00:00:00 2001 From: "Guilherme G. Piccoli" Date: Wed, 23 Mar 2022 16:07:09 -0700 Subject: panic: move panic_print before kmsg dumpers The panic_print setting allows users to collect more information in a panic event, like memory stats, tasks, CPUs backtraces, etc. This is an interesting debug mechanism, but currently the print event happens *after* kmsg_dump(), meaning that pstore, for example, cannot collect a dmesg with the panic_print extra information. This patch changes that in 2 steps: (a) The panic_print setting allows to replay the existing kernel log buffer to the console (bit 5), besides the extra information dump. This functionality makes sense only at the end of the panic() function. So, we hereby allow to distinguish the two situations by a new boolean parameter in the function panic_print_sys_info(). (b) With the above change, we can safely call panic_print_sys_info() before kmsg_dump(), allowing to dump the extra information when using pstore or other kmsg dumpers. The additional messages from panic_print could overwrite the oldest messages when the buffer is full. The only reasonable solution is to use a large enough log buffer, hence we added an advice into the kernel parameters documentation about that. Link: https://lkml.kernel.org/r/20220214141308.841525-1-gpiccoli@igalia.com Signed-off-by: Guilherme G. Piccoli Acked-by: Baoquan He Reviewed-by: Petr Mladek Reviewed-by: Sergey Senozhatsky Cc: Feng Tang Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- kernel/panic.c | 13 +++++++++---- 1 file changed, 9 insertions(+), 4 deletions(-) (limited to 'kernel/panic.c') diff --git a/kernel/panic.c b/kernel/panic.c index 3c3fb36d8d41..eb4dfb932c85 100644 --- a/kernel/panic.c +++ b/kernel/panic.c @@ -148,10 +148,13 @@ void nmi_panic(struct pt_regs *regs, const char *msg) } EXPORT_SYMBOL(nmi_panic); -static void panic_print_sys_info(void) +static void panic_print_sys_info(bool console_flush) { - if (panic_print & PANIC_PRINT_ALL_PRINTK_MSG) - console_flush_on_panic(CONSOLE_REPLAY_ALL); + if (console_flush) { + if (panic_print & PANIC_PRINT_ALL_PRINTK_MSG) + console_flush_on_panic(CONSOLE_REPLAY_ALL); + return; + } if (panic_print & PANIC_PRINT_ALL_CPU_BT) trigger_all_cpu_backtrace(); @@ -286,6 +289,8 @@ void panic(const char *fmt, ...) */ atomic_notifier_call_chain(&panic_notifier_list, 0, buf); + panic_print_sys_info(false); + kmsg_dump(KMSG_DUMP_PANIC); /* @@ -316,7 +321,7 @@ void panic(const char *fmt, ...) debug_locks_off(); console_flush_on_panic(CONSOLE_FLUSH_PENDING); - panic_print_sys_info(); + panic_print_sys_info(true); if (!panic_blink) panic_blink = no_blink; -- cgit