[RFC PATCH v3 05/12] lib: vdso: Avoid duplication in __cvdso_clock_getres()

[Christophe Leroy]

VDSO_HRES and VDSO_RAW clocks are handled the same way.

Don't duplicate code.

Before the patch:
clock-getres-monotonic-raw:    vdso: 737 nsec/call
clock-getres-monotonic-coarse:    vdso: 753 nsec/call
clock-getres-monotonic:    vdso: 691 nsec/call

After the patch:
clock-getres-monotonic-raw:    vdso: 715 nsec/call
clock-getres-monotonic-coarse:    vdso: 715 nsec/call
clock-getres-monotonic:    vdso: 714 nsec/call

Signed-off-by: Christophe Leroy <christophe.le...@c-s.fr>
Reviewed-by: Andy Lutomirski <l...@kernel.org>
---
 lib/vdso/gettimeofday.c | 11 ++---------
 1 file changed, 2 insertions(+), 9 deletions(-)

diff --git a/lib/vdso/gettimeofday.c b/lib/vdso/gettimeofday.c
index d75e44ba716f..decd3f2b37af 100644
--- a/lib/vdso/gettimeofday.c
+++ b/lib/vdso/gettimeofday.c
@@ -184,7 +184,6 @@ static __maybe_unused
 int __cvdso_clock_getres_common(clockid_t clock, struct __kernel_timespec *res)
 {
        const struct vdso_data *vd = __arch_get_vdso_data();
-       u64 hrtimer_res;
        u32 msk;
        u64 ns;
 
@@ -192,27 +191,21 @@ int __cvdso_clock_getres_common(clockid_t clock, struct 
__kernel_timespec *res)
        if (unlikely((u32) clock >= MAX_CLOCKS))
                return -1;
 
-       hrtimer_res = READ_ONCE(vd[CS_HRES_COARSE].hrtimer_res);
        /*
         * Convert the clockid to a bitmask and use it to check which
         * clocks are handled in the VDSO directly.
         */
        msk = 1U << clock;
-       if (msk & VDSO_HRES) {
+       if (msk & (VDSO_HRES | VDSO_RAW)) {
                /*
                 * Preserves the behaviour of posix_get_hrtimer_res().
                 */
-               ns = hrtimer_res;
+               ns = READ_ONCE(vd[CS_HRES_COARSE].hrtimer_res);
        } else if (msk & VDSO_COARSE) {
                /*
                 * Preserves the behaviour of posix_get_coarse_res().
                 */
                ns = LOW_RES_NSEC;
-       } else if (msk & VDSO_RAW) {
-               /*
-                * Preserves the behaviour of posix_get_hrtimer_res().
-                */
-               ns = hrtimer_res;
        } else {
                return -1;
        }
-- 
2.13.3