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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: 44f57d788e ("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
This commit is contained in:
Arnd Bergmann 2019-07-10 15:01:53 +02:00 committed by Thomas Gleixner
parent 9bdd7bb3a8
commit 0df1c9868c
1 changed files with 1 additions and 5 deletions
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6
kernel/time/vsyscall.c
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@ -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);