timekeeping/vsyscall: Use __iter_div_u64_rem()

On 32-bit x86 when building with clang-9, the 'division' loop gets turned
back into an inefficient division that causes a link error:

kernel/time/vsyscall.o: In function `update_vsyscall':
vsyscall.c:(.text+0xe3): undefined reference to `__udivdi3'

Use the existing __iter_div_u64_rem() function which is used to address the
same issue in other places.

Fixes: 44f57d788e7d ("timekeeping: Provide a generic update_vsyscall() implementation")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Nathan Chancellor <natechancellor@gmail.com>
Tested-by: Nathan Chancellor <natechancellor@gmail.com>
Link: https://lkml.kernel.org/r/20190710130206.1670830-1-arnd@arndb.de

1 files changed, 1 insertions, 5 deletions

diff --git a/kernel/time/vsyscall.c b/kernel/time/vsyscall.c
index a80893180826..8cf3596a4ce6 100644
--- a/kernel/time/vsyscall.c
+++ b/kernel/time/vsyscall.c
@@ -104,11 +104,7 @@ void update_vsyscall(struct timekeeper *tk)
         vdso_ts->sec    = tk->xtime_sec + tk->wall_to_monotonic.tv_sec;
         nsec            = tk->tkr_mono.xtime_nsec >> tk->tkr_mono.shift;
         nsec            = nsec + tk->wall_to_monotonic.tv_nsec;
-        while (nsec >= NSEC_PER_SEC) {
-                nsec = nsec - NSEC_PER_SEC;
-                vdso_ts->sec++;
-        }
-        vdso_ts->nsec   = nsec;
+        vdso_ts->sec    += __iter_div_u64_rem(nsec, NSEC_PER_SEC, &vdso_ts->nsec);
 
         if (__arch_use_vsyscall(vdata))
                 update_vdso_data(vdata, tk);