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authorAndi Kleen <ak@linux.intel.com>2017-11-17 15:27:03 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2017-11-17 16:10:00 -0800
commitb1fca27d384e8418aac84b39f6f5179aecc1b64f (patch)
treee08be97de59a1cbb16df46273aadef161358b8ba
parentfb6cc4ac15c354fa1eb449f50a0dfe5f4bf0d42a (diff)
download96b-common-b1fca27d384e8418aac84b39f6f5179aecc1b64f.tar.gz
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@linux-foundation.org: coding-style fixes] Link: http://lkml.kernel.org/r/20171017221455.6740-1-andi@firstfloor.org Signed-off-by: Andi Kleen <ak@linux.intel.com> Tested-by: Michael Ellerman <mpe@ellerman.id.au> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
-rw-r--r--Documentation/clearing-warn-once.txt7
-rw-r--r--include/asm-generic/bug.h6
-rw-r--r--include/asm-generic/sections.h1
-rw-r--r--include/asm-generic/vmlinux.lds.h3
-rw-r--r--kernel/panic.c28
5 files changed, 42 insertions, 3 deletions
diff --git a/Documentation/clearing-warn-once.txt b/Documentation/clearing-warn-once.txt
new file mode 100644
index 000000000000..5b1f5d547be1
--- /dev/null
+++ b/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 --git a/include/asm-generic/bug.h b/include/asm-generic/bug.h
index af2cc94a61bf..7844b0df88cd 100644
--- a/include/asm-generic/bug.h
+++ b/include/asm-generic/bug.h
@@ -130,7 +130,7 @@ void __warn(const char *file, int line, void *caller, unsigned taint,
#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, void *caller, unsigned taint,
#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, void *caller, unsigned taint,
})
#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 --git a/include/asm-generic/sections.h b/include/asm-generic/sections.h
index 6d9576931084..03cc5f9bba71 100644
--- a/include/asm-generic/sections.h
+++ b/include/asm-generic/sections.h
@@ -44,6 +44,7 @@ extern char __entry_text_start[], __entry_text_end[];
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 --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h
index bdcd1caae092..ee8b707d9fa9 100644
--- a/include/asm-generic/vmlinux.lds.h
+++ b/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 --git a/kernel/panic.c b/kernel/panic.c
index bdd18afa19a4..672a91dc20fe 100644
--- a/kernel/panic.c
+++ b/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, int line)
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
/*