From 9a6b55ac4a44060bcb782baf002859b2a2c63267 Mon Sep 17 00:00:00 2001 From: Thomas Gleixner Date: Tue, 14 Jan 2020 19:52:38 +0100 Subject: lib/vdso: Make __arch_update_vdso_data() logic understandable The function name suggests that this is a boolean checking whether the architecture asks for an update of the VDSO data, but it works the other way round. To spare further confusion invert the logic. Fixes: 44f57d788e7d ("timekeeping: Provide a generic update_vsyscall() implementation") Signed-off-by: Thomas Gleixner Link: https://lore.kernel.org/r/20200114185946.656652824@linutronix.de --- kernel/time/vsyscall.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'kernel') diff --git a/kernel/time/vsyscall.c b/kernel/time/vsyscall.c index 5ee0f7709410..f0aab6182824 100644 --- a/kernel/time/vsyscall.c +++ b/kernel/time/vsyscall.c @@ -84,7 +84,7 @@ void update_vsyscall(struct timekeeper *tk) struct vdso_timestamp *vdso_ts; u64 nsec; - if (__arch_update_vdso_data()) { + if (!__arch_update_vdso_data()) { /* * Some architectures might want to skip the update of the * data page. -- cgit v1.2.3 From 9f24c540f7f8eb3a981528da9a9a636a5bdf5987 Mon Sep 17 00:00:00 2001 From: Thomas Gleixner Date: Tue, 14 Jan 2020 19:52:39 +0100 Subject: lib/vdso: Update coarse timekeeper unconditionally The low resolution parts of the VDSO, i.e.: clock_gettime(CLOCK_*_COARSE), clock_getres(), time() can be used even if there is no VDSO capable clocksource. But if an architecture opts out of the VDSO data update then this information becomes stale. This affects ARM when there is no architected timer available. The lack of update causes userspace to use stale data forever. Make the update of the low resolution parts unconditional and only skip the update of the high resolution parts if the architecture requests it. Fixes: 44f57d788e7d ("timekeeping: Provide a generic update_vsyscall() implementation") Signed-off-by: Thomas Gleixner Link: https://lore.kernel.org/r/20200114185946.765577901@linutronix.de --- kernel/time/vsyscall.c | 37 +++++++++++++++++-------------------- 1 file changed, 17 insertions(+), 20 deletions(-) (limited to 'kernel') diff --git a/kernel/time/vsyscall.c b/kernel/time/vsyscall.c index f0aab6182824..9577c89179cd 100644 --- a/kernel/time/vsyscall.c +++ b/kernel/time/vsyscall.c @@ -28,11 +28,6 @@ static inline void update_vdso_data(struct vdso_data *vdata, vdata[CS_RAW].mult = tk->tkr_raw.mult; vdata[CS_RAW].shift = tk->tkr_raw.shift; - /* CLOCK_REALTIME */ - vdso_ts = &vdata[CS_HRES_COARSE].basetime[CLOCK_REALTIME]; - vdso_ts->sec = tk->xtime_sec; - vdso_ts->nsec = tk->tkr_mono.xtime_nsec; - /* CLOCK_MONOTONIC */ vdso_ts = &vdata[CS_HRES_COARSE].basetime[CLOCK_MONOTONIC]; vdso_ts->sec = tk->xtime_sec + tk->wall_to_monotonic.tv_sec; @@ -70,12 +65,6 @@ static inline void update_vdso_data(struct vdso_data *vdata, vdso_ts = &vdata[CS_HRES_COARSE].basetime[CLOCK_TAI]; vdso_ts->sec = tk->xtime_sec + (s64)tk->tai_offset; vdso_ts->nsec = tk->tkr_mono.xtime_nsec; - - /* - * Read without the seqlock held by clock_getres(). - * Note: No need to have a second copy. - */ - WRITE_ONCE(vdata[CS_HRES_COARSE].hrtimer_res, hrtimer_resolution); } void update_vsyscall(struct timekeeper *tk) @@ -84,20 +73,17 @@ void update_vsyscall(struct timekeeper *tk) struct vdso_timestamp *vdso_ts; u64 nsec; - if (!__arch_update_vdso_data()) { - /* - * Some architectures might want to skip the update of the - * data page. - */ - return; - } - /* copy vsyscall data */ vdso_write_begin(vdata); vdata[CS_HRES_COARSE].clock_mode = __arch_get_clock_mode(tk); vdata[CS_RAW].clock_mode = __arch_get_clock_mode(tk); + /* CLOCK_REALTIME also required for time() */ + vdso_ts = &vdata[CS_HRES_COARSE].basetime[CLOCK_REALTIME]; + vdso_ts->sec = tk->xtime_sec; + vdso_ts->nsec = tk->tkr_mono.xtime_nsec; + /* CLOCK_REALTIME_COARSE */ vdso_ts = &vdata[CS_HRES_COARSE].basetime[CLOCK_REALTIME_COARSE]; vdso_ts->sec = tk->xtime_sec; @@ -110,7 +96,18 @@ void update_vsyscall(struct timekeeper *tk) nsec = nsec + tk->wall_to_monotonic.tv_nsec; vdso_ts->sec += __iter_div_u64_rem(nsec, NSEC_PER_SEC, &vdso_ts->nsec); - update_vdso_data(vdata, tk); + /* + * Read without the seqlock held by clock_getres(). + * Note: No need to have a second copy. + */ + WRITE_ONCE(vdata[CS_HRES_COARSE].hrtimer_res, hrtimer_resolution); + + /* + * Architectures can opt out of updating the high resolution part + * of the VDSO. + */ + if (__arch_update_vdso_data()) + update_vdso_data(vdata, tk); __arch_update_vsyscall(vdata, tk); -- cgit v1.2.3