From: Andi Kleen <ak@xxxxxxxxxxxxxxx> Subject: kernel debug: support resetting WARN*_ONCE I like _ONCE warnings because it's guaranteed that they don't flood the log. During testing I find it useful to reset the state of the once warnings, so that I can rerun tests and see if they trigger again, or can guarantee that a test run always hits the same warnings. This patch adds a debugfs interface to reset all the _ONCE warnings so that they appear again: echo 1 > /sys/kernel/debug/clear_warn_once This is implemented by putting all the warning booleans into a special section, and clearing it. [akpm@xxxxxxxxxxxxxxxxxxxx: coding-style fixes] Link: http://lkml.kernel.org/r/20171017221455.6740-1-andi@xxxxxxxxxxxxxx Signed-off-by: Andi Kleen <ak@xxxxxxxxxxxxxxx> Tested-by: Michael Ellerman <mpe@xxxxxxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- Documentation/clearing-warn-once.txt | 7 ++++++ include/asm-generic/bug.h | 6 ++--- include/asm-generic/sections.h | 1 include/asm-generic/vmlinux.lds.h | 3 ++ kernel/panic.c | 28 +++++++++++++++++++++++++ 5 files changed, 42 insertions(+), 3 deletions(-) diff -puN /dev/null Documentation/clearing-warn-once.txt --- /dev/null +++ a/Documentation/clearing-warn-once.txt @@ -0,0 +1,7 @@ + +WARN_ONCE / WARN_ON_ONCE only print a warning once. + +echo 1 > /sys/kernel/debug/clear_warn_once + +clears the state and allows the warnings to print once again. +This can be useful after test suite runs to reproduce problems. diff -puN include/asm-generic/bug.h~support-resetting-warn_once include/asm-generic/bug.h --- a/include/asm-generic/bug.h~support-resetting-warn_once +++ a/include/asm-generic/bug.h @@ -130,7 +130,7 @@ void __warn(const char *file, int line, #ifndef WARN_ON_ONCE #define WARN_ON_ONCE(condition) ({ \ - static bool __section(.data.unlikely) __warned; \ + static bool __section(.data.once) __warned; \ int __ret_warn_once = !!(condition); \ \ if (unlikely(__ret_warn_once && !__warned)) { \ @@ -142,7 +142,7 @@ void __warn(const char *file, int line, #endif #define WARN_ONCE(condition, format...) ({ \ - static bool __section(.data.unlikely) __warned; \ + static bool __section(.data.once) __warned; \ int __ret_warn_once = !!(condition); \ \ if (unlikely(__ret_warn_once && !__warned)) { \ @@ -153,7 +153,7 @@ void __warn(const char *file, int line, }) #define WARN_TAINT_ONCE(condition, taint, format...) ({ \ - static bool __section(.data.unlikely) __warned; \ + static bool __section(.data.once) __warned; \ int __ret_warn_once = !!(condition); \ \ if (unlikely(__ret_warn_once && !__warned)) { \ diff -puN include/asm-generic/sections.h~support-resetting-warn_once include/asm-generic/sections.h --- a/include/asm-generic/sections.h~support-resetting-warn_once +++ a/include/asm-generic/sections.h @@ -44,6 +44,7 @@ extern char __entry_text_start[], __entr extern char __start_rodata[], __end_rodata[]; extern char __irqentry_text_start[], __irqentry_text_end[]; extern char __softirqentry_text_start[], __softirqentry_text_end[]; +extern char __start_once[], __end_once[]; /* Start and end of .ctors section - used for constructor calls. */ extern char __ctors_start[], __ctors_end[]; diff -puN include/asm-generic/vmlinux.lds.h~support-resetting-warn_once include/asm-generic/vmlinux.lds.h --- a/include/asm-generic/vmlinux.lds.h~support-resetting-warn_once +++ a/include/asm-generic/vmlinux.lds.h @@ -223,6 +223,9 @@ MEM_KEEP(init.data) \ MEM_KEEP(exit.data) \ *(.data.unlikely) \ + VMLINUX_SYMBOL(__start_once) = .; \ + *(.data.once) \ + VMLINUX_SYMBOL(__end_once) = .; \ STRUCT_ALIGN(); \ *(__tracepoints) \ /* implement dynamic printk debug */ \ diff -puN kernel/panic.c~support-resetting-warn_once kernel/panic.c --- a/kernel/panic.c~support-resetting-warn_once +++ a/kernel/panic.c @@ -27,6 +27,8 @@ #include <linux/console.h> #include <linux/bug.h> #include <linux/ratelimit.h> +#include <linux/debugfs.h> +#include <asm/sections.h> #define PANIC_TIMER_STEP 100 #define PANIC_BLINK_SPD 18 @@ -587,6 +589,32 @@ void warn_slowpath_null(const char *file EXPORT_SYMBOL(warn_slowpath_null); #endif +#ifdef CONFIG_BUG + +/* Support resetting WARN*_ONCE state */ + +static int clear_warn_once_set(void *data, u64 val) +{ + memset(__start_once, 0, __end_once - __start_once); + return 0; +} + +DEFINE_SIMPLE_ATTRIBUTE(clear_warn_once_fops, + NULL, + clear_warn_once_set, + "%lld\n"); + +static __init int register_warn_debugfs(void) +{ + /* Don't care about failure */ + debugfs_create_file("clear_warn_once", 0644, NULL, + NULL, &clear_warn_once_fops); + return 0; +} + +device_initcall(register_warn_debugfs); +#endif + #ifdef CONFIG_CC_STACKPROTECTOR /* _ -- To unsubscribe from this list: send the line "unsubscribe mm-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
