Andrew Morton wrote:
Yup, this change will fix some compile warnings which will never be
fixed in any other way for mips.
+static inline void __noreturn BUG(void)
+{
+ __asm__ __volatile__("break %0" : : "i" (BRK_BUG));
+ /* Fool GCC into thinking the function doesn't return. */
+ while (1)
+ ;
+}
This kind of sucks, doesn't it? It adds instructions into the kernel
text, very frequently on fast paths. Those instructions are never
executed, and we're blowing away i-cache just to quash compiler
warnings.
For example, this:
--- a/arch/x86/include/asm/bug.h~a
+++ a/arch/x86/include/asm/bug.h
@@ -22,14 +22,12 @@ do {
\
".popsection" \
: : "i" (__FILE__), "i" (__LINE__), \
"i" (sizeof(struct bug_entry))); \
- for (;;) ; \
} while (0)
#else
#define BUG() \
do { \
asm volatile("ud2"); \
- for (;;) ; \
} while (0)
#endif
_
reduces the size of i386 mm/vmalloc.o text by 56 bytes.
I wonder if there is any clever way in which we can do this without
introducing additional runtime cost.
As I said in the other part of the thread, We are working on a GCC patch
that adds a new built-in function '__builtin_noreturn()', that you could
substitute for 'for(;;);' that emits no instructions in this case.
David Daney
