[RFC PATCH v4 03/11] lib: vdso: only read hrtimer_res when needed in __cvdso_clock_getres()

Christophe Leroy christophe.leroy at c-s.fr
Thu Jan 16 09:58:27 PST 2020


Only perform READ_ONCE(vd[CS_HRES_COARSE].hrtimer_res) for
HRES and RAW clocks.

Signed-off-by: Christophe Leroy <christophe.leroy at c-s.fr>
---
 lib/vdso/gettimeofday.c | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/lib/vdso/gettimeofday.c b/lib/vdso/gettimeofday.c
index 9563be3cb5fa..8b3084d9a3ec 100644
--- a/lib/vdso/gettimeofday.c
+++ b/lib/vdso/gettimeofday.c
@@ -326,7 +326,6 @@ 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;
 
@@ -338,7 +337,6 @@ int __cvdso_clock_getres_common(clockid_t clock, struct __kernel_timespec *res)
 	    vd->clock_mode == VDSO_CLOCKMODE_TIMENS)
 		vd = __arch_get_timens_vdso_data();
 
-	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.
@@ -348,7 +346,7 @@ int __cvdso_clock_getres_common(clockid_t clock, struct __kernel_timespec *res)
 		/*
 		 * 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().
-- 
2.13.3




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