linux-kernel - [RFC PATCH v3 05/12] lib: vdso: Avoid duplication in __cvdso_clock

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Date:   Mon, 13 Jan 2020 17:08:43 +0000 (UTC)
From:   Christophe Leroy <christophe.leroy@....fr>
To:     Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        Michael Ellerman <mpe@...erman.id.au>, arnd@...db.de,
        tglx@...utronix.de, vincenzo.frascino@....com, luto@...nel.org
Cc:     linux-kernel@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
        linux-arm-kernel@...ts.infradead.org, linux-mips@...r.kernel.org,
        x86@...nel.org
Subject: [RFC PATCH v3 05/12] lib: vdso: Avoid duplication in
 __cvdso_clock_getres()

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.leroy@....fr>
Reviewed-by: Andy Lutomirski <luto@...nel.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