The patch titled
Subject: kernel debug: support resetting WARN*_ONCE
has been added to the -mm tree. Its filename is
support-resetting-warn_once.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/support-resetting-warn_once.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/support-resetting-warn_once.patch
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*** Remember to use Documentation/SubmitChecklist when testing your code ***
The -mm tree is included into linux-next and is updated
there every 3-4 working days
------------------------------------------------------
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.
Link: http://lkml.kernel.org/r/20171017221455.6740-1-andi@xxxxxxxxxxxxxx
Signed-off-by: Andi Kleen <ak@xxxxxxxxxxxxxxx>
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
@@ -129,7 +129,7 @@ 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)) { \
@@ -141,7 +141,7 @@ 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)) { \
@@ -152,7 +152,7 @@ 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
@@ -43,6 +43,7 @@ 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;
+}
+
+__initcall(register_warn_debugfs);
+#endif
+
#ifdef CONFIG_CC_STACKPROTECTOR
/*
_
Patches currently in -mm which might be from ak@xxxxxxxxxxxxxxx are
support-resetting-warn_once.patch
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