@@ -110,9 +110,10 @@ extern void warn_slowpath_null(const char *file, const int line);
static bool __section(.data.unlikely) __warned; \
int __ret_warn_once = !!(condition); \
\
- if (unlikely(__ret_warn_once)) \
- if (WARN_ON(!__warned)) \
- __warned = true; \
+ if (unlikely(__ret_warn_once) && !__warned) { \
+ __warned = true; \
+ WARN_ON(true); \
+ } \
unlikely(__ret_warn_once); \
})
@@ -120,9 +121,10 @@ extern void warn_slowpath_null(const char *file, const int line);
static bool __section(.data.unlikely) __warned; \
int __ret_warn_once = !!(condition); \
\
- if (unlikely(__ret_warn_once)) \
- if (WARN(!__warned, format)) \
- __warned = true; \
+ if (unlikely(__ret_warn_once) && !__warned) { \
+ __warned = true; \
+ WARN(true, format); \
+ } \
unlikely(__ret_warn_once); \
})
@@ -130,9 +132,10 @@ extern void warn_slowpath_null(const char *file, const int line);
static bool __section(.data.unlikely) __warned; \
int __ret_warn_once = !!(condition); \
\
- if (unlikely(__ret_warn_once)) \
- if (WARN_TAINT(!__warned, taint, format)) \
- __warned = true; \
+ if (unlikely(__ret_warn_once) && !__warned) { \
+ __warned = true; \
+ WARN_TAINT(true, taint, format); \
+ } \
unlikely(__ret_warn_once); \
})
Currently WARN_ONCE() and similar macros set __warned *after* calling the underlying macro. This risks infinite recursion if WARN_ONCE() is used to implement sanity tests in any code that can be called by printk. This can be fixed by restructuring the macros to set __warned before calling further macros. Signed-off-by: Daniel Thompson <daniel.thompson@linaro.org> --- Notes: I discovered this problem when I temporarily added sanity tests to the irqflags macros during some of my development work but I suspect the scope is a little wider. I admit I was tempted to throw this change away after I had finished debugging but for two things prompted me to post it. 1. It did cost me a few minutes head scratching and I'd like to spare others the pain. 2. I realized the new code is potentially (and very fractionally) more efficient: the register containing address of __warned can be reused and a cache hit is a near certainty for the write. Don't get too excited about the efficiency gains though they are extremely modest. Measures as code size benefit and using v4.0-rc4 the results are: Kernel GCC version Code size reduction arm multi_v7_defconfig Linaro 4.8-2014.01 224 bytes arm64 defconfig Linaro 4.9-2014.09 32 bytes i386_defconfig Redhat 4.9.2-6 62 bytes x86_64_defconfig Redhat 4.9.2-6 380 bytes include/asm-generic/bug.h | 21 ++++++++++++--------- 1 file changed, 12 insertions(+), 9 deletions(-) -- 2.1.0