From f5b973489beb1a1239dfad53e3ad6e36ff7ee958 Mon Sep 17 00:00:00 2001 From: Segher Boessenkool Date: Thu, 9 Oct 2008 21:18:27 +0100 Subject: [PATCH] fix-gcc-4.3-false-modulo-optimization.patch I tried to compile the current stable kernel (a2ef813d2f439a3e9f377d33a2e5baad098afb7e) and get the following errors: kernel/built-in.o: In function `timespec_add_ns': /mnt/data/Freerunner/Gentoo/rootinstall/usr/src/linux/include/linux/time.h:174: undefined reference to `__aeabi_uldivmod' /mnt/data/Freerunner/Gentoo/rootinstall/usr/src/linux/include/linux/time.h:179: undefined reference to `__aeabi_uldivmod' /mnt/data/Freerunner/Gentoo/rootinstall/usr/src/linux/include/linux/time.h:174: undefined reference to `__aeabi_uldivmod' /mnt/data/Freerunner/Gentoo/rootinstall/usr/src/linux/include/linux/time.h:179: undefined reference to `__aeabi_uldivmod' applying the following patch solved the problem: -------- Prevent gcc-4.3 form "optimizing" the while loop into a costly modulo operation. Patch found at http://lkml.org/lkml/2008/2/22/464. Reported-by: Sven Rebhan Signed-off-by: Segher Boessenkool --- include/linux/time.h | 4 ++++ 1 files changed, 4 insertions(+), 0 deletions(-) diff --git a/include/linux/time.h b/include/linux/time.h index b04136d..3e8fd9e 100644 --- a/include/linux/time.h +++ b/include/linux/time.h @@ -173,6 +173,10 @@ static inline void timespec_add_ns(struct timespec *a, u64 ns) { ns += a->tv_nsec; while(unlikely(ns >= NSEC_PER_SEC)) { + /* The following asm() prevents the compiler from + * optimising this loop into a modulo operation. */ + asm("" : "+r"(ns)); + ns -= NSEC_PER_SEC; a->tv_sec++; } -- 1.5.6.5