Use do_div for a subtract loop

PATCH New Thiemo Seufer 1 participant 1 message May 1, 2007

Subsystems (2)

MIPS Timekeeping, clocksource core, NTP, alarmtimer

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Thiemo Seufer

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2007-05-01 18:10 UTC #0 lore raw

PATCH 1/1 Use do_div for a subtract loop

Hello All,

this patch switches the subtract loop in timespec_add_ns to use do_div. The latest GCC SVN version grew intelligent enough to optimize the loop to a division which calls libgcc's __udivdi3, which breaks kernel builds.

Tested by building and booting a little endian qemu MIPS kernel.

Thiemo

Signed-off-by Thiemo Seufer <[email protected]>

include/linux/time.h +5 -3

index 8ea8dea..e1a11d7 100644
@@ -5,6 +5,7 @@
 
 #ifdef __KERNEL__
 # include <linux/seqlock.h>
+# include <asm/div64.h>
 #endif
 
 #ifndef _STRUCT_TIMESPEC

@@ -169,9 +170,10 @@ extern struct timeval ns_to_timeval(const s64 nsec);
 static inline void timespec_add_ns(struct timespec *a, u64 ns)
 {
 	ns += a->tv_nsec;
-	while(unlikely(ns >= NSEC_PER_SEC)) {
-		ns -= NSEC_PER_SEC;
-		a->tv_sec++;
+	if(unlikely(ns >= NSEC_PER_SEC)) {
+		u64 tmp = ns;
+		ns = do_div(tmp, NSEC_PER_SEC);
+		a->tv_sec += tmp;
 	}
 	a->tv_nsec = ns;
 }