From d988d9a9b9d180bfd5c1d353b3b176cb90d6861b Mon Sep 17 00:00:00 2001 From: John Ogness Date: Wed, 7 Feb 2024 14:47:02 +0106 Subject: panic: Flush kernel log buffer at the end If the kernel crashes in a context where printk() calls always defer printing (such as in NMI or inside a printk_safe section) then the final panic messages will be deferred to irq_work. But if irq_work is not available, the messages will not get printed unless explicitly flushed. The result is that the final "end Kernel panic" banner does not get printed. Add one final flush after the last printk() call to make sure the final panic messages make it out as well. Signed-off-by: John Ogness Reviewed-by: Petr Mladek Link: https://lore.kernel.org/r/20240207134103.1357162-14-john.ogness@linutronix.de Signed-off-by: Petr Mladek --- kernel/panic.c | 8 ++++++++ 1 file changed, 8 insertions(+) (limited to 'kernel/panic.c') diff --git a/kernel/panic.c b/kernel/panic.c index 2807639aab51..f22d8f33ea14 100644 --- a/kernel/panic.c +++ b/kernel/panic.c @@ -446,6 +446,14 @@ void panic(const char *fmt, ...) /* Do not scroll important messages printed above */ suppress_printk = 1; + + /* + * The final messages may not have been printed if in a context that + * defers printing (such as NMI) and irq_work is not available. + * Explicitly flush the kernel log buffer one last time. + */ + console_flush_on_panic(CONSOLE_FLUSH_PENDING); + local_irq_enable(); for (i = 0; ; i += PANIC_TIMER_STEP) { touch_softlockup_watchdog(); -- cgit v1.2.3 From b73aa539a7789d2366aa7ffa627cede77d6f1c4e Mon Sep 17 00:00:00 2001 From: Baoquan He Date: Sun, 7 Jan 2024 17:16:41 +0800 Subject: panic: suppress gnu_printf warning with GCC 13.2.1 and W=1, there's compiling warning like this: kernel/panic.c: In function `__warn': kernel/panic.c:676:17: warning: function `__warn' might be a candidate for `gnu_printf' format attribute [-Wsuggest-attribute=format] 676 | vprintk(args->fmt, args->args); | ^~~~~~~ The normal __printf(x,y) adding can't fix it. So add workaround which disables -Wsuggest-attribute=format to mute it. Link: https://lkml.kernel.org/r/20240107091641.579849-1-bhe@redhat.com Signed-off-by: Baoquan He Signed-off-by: Andrew Morton --- kernel/panic.c | 5 +++++ 1 file changed, 5 insertions(+) (limited to 'kernel/panic.c') diff --git a/kernel/panic.c b/kernel/panic.c index 2807639aab51..d49b68184c56 100644 --- a/kernel/panic.c +++ b/kernel/panic.c @@ -666,8 +666,13 @@ void __warn(const char *file, int line, void *caller, unsigned taint, pr_warn("WARNING: CPU: %d PID: %d at %pS\n", raw_smp_processor_id(), current->pid, caller); +#pragma GCC diagnostic push +#ifndef __clang__ +#pragma GCC diagnostic ignored "-Wsuggest-attribute=format" +#endif if (args) vprintk(args->fmt, args->args); +#pragma GCC diagnostic pop print_modules(); -- cgit v1.2.3 From 2e3fc6ca521499a985a1829a21759ac25359c0f3 Mon Sep 17 00:00:00 2001 From: Feng Tang Date: Fri, 2 Feb 2024 21:20:42 +0800 Subject: panic: add option to dump blocked tasks in panic_print For debugging kernel panics and other bugs, there is already an option of panic_print to dump all tasks' call stacks. On today's large servers running many containers, there could be thousands of tasks or more, and this will print out huge amount of call stacks, taking a lot of time (for serial console which is main target user case of panic_print). And in many cases, only those several tasks being blocked are key for the panic, so add an option to only dump blocked tasks' call stacks. [akpm@linux-foundation.org: clarify documentation a little] Link: https://lkml.kernel.org/r/20240202132042.3609657-1-feng.tang@intel.com Signed-off-by: Feng Tang Tested-by: Guilherme G. Piccoli Cc: Jonathan Corbet Cc: Josh Poimboeuf Cc: Peter Zijlstra (Intel) Cc: Randy Dunlap Signed-off-by: Andrew Morton --- Documentation/admin-guide/kernel-parameters.txt | 1 + Documentation/admin-guide/sysctl/kernel.rst | 1 + kernel/panic.c | 4 ++++ 3 files changed, 6 insertions(+) (limited to 'kernel/panic.c') diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt index 31b3a25680d0..800b4b5dcbb4 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -4182,6 +4182,7 @@ bit 4: print ftrace buffer bit 5: print all printk messages in buffer bit 6: print all CPUs backtrace (if available in the arch) + bit 7: print only tasks in uninterruptible (blocked) state *Be aware* that this option may print a _lot_ of lines, so there are risks of losing older messages in the log. Use this option carefully, maybe worth to setup a diff --git a/Documentation/admin-guide/sysctl/kernel.rst b/Documentation/admin-guide/sysctl/kernel.rst index bc578663619d..a9b71190399d 100644 --- a/Documentation/admin-guide/sysctl/kernel.rst +++ b/Documentation/admin-guide/sysctl/kernel.rst @@ -853,6 +853,7 @@ bit 3 print locks info if ``CONFIG_LOCKDEP`` is on bit 4 print ftrace buffer bit 5 print all printk messages in buffer bit 6 print all CPUs backtrace (if available in the arch) +bit 7 print only tasks in uninterruptible (blocked) state ===== ============================================ So for example to print tasks and memory info on panic, user can:: diff --git a/kernel/panic.c b/kernel/panic.c index d49b68184c56..d4cb86d97f8f 100644 --- a/kernel/panic.c +++ b/kernel/panic.c @@ -73,6 +73,7 @@ EXPORT_SYMBOL_GPL(panic_timeout); #define PANIC_PRINT_FTRACE_INFO 0x00000010 #define PANIC_PRINT_ALL_PRINTK_MSG 0x00000020 #define PANIC_PRINT_ALL_CPU_BT 0x00000040 +#define PANIC_PRINT_BLOCKED_TASKS 0x00000080 unsigned long panic_print; ATOMIC_NOTIFIER_HEAD(panic_notifier_list); @@ -227,6 +228,9 @@ static void panic_print_sys_info(bool console_flush) if (panic_print & PANIC_PRINT_FTRACE_INFO) ftrace_dump(DUMP_ALL); + + if (panic_print & PANIC_PRINT_BLOCKED_TASKS) + show_state_filter(TASK_UNINTERRUPTIBLE); } void check_panic_on_warn(const char *origin) -- cgit v1.2.3