On Mon, 1 Apr 2019 12:51:50 +0100 Vincenzo Frascino <vincenzo.frascino@xxxxxxx> wrote: > clock_getres in the vDSO library has to preserve the same behaviour > of posix_get_hrtimer_res(). > > In particular, posix_get_hrtimer_res() does: > sec = 0; > ns = hrtimer_resolution; > and hrtimer_resolution depends on the enablement of the high > resolution timers that can happen either at compile or at run time. > > Fix the s390 vdso implementation of clock_getres keeping a copy of > hrtimer_resolution in vdso data and using that directly. > > Cc: Martin Schwidefsky <schwidefsky@xxxxxxxxxx> > Cc: Heiko Carstens <heiko.carstens@xxxxxxxxxx> > Signed-off-by: Vincenzo Frascino <vincenzo.frascino@xxxxxxx> > --- > arch/s390/include/asm/vdso.h | 1 + > arch/s390/kernel/asm-offsets.c | 2 +- > arch/s390/kernel/time.c | 1 + > arch/s390/kernel/vdso32/clock_getres.S | 17 ++++++++++++----- > arch/s390/kernel/vdso64/clock_getres.S | 15 ++++++++++----- > 5 files changed, 25 insertions(+), 11 deletions(-) I tried this patch and in principle this works. In that regard Acked-by: Martin Schwidefsky <schwidefsky@xxxxxxxxxx> But I wonder if the loop to check the update counter is really necessary. The hrtimer_resolution value can only changes once with the first call to hrtimer_switch_to_hres(). With the TOD clock as the only clock available on s390 we always have the ability to do hrtimer. It then all depends on the highres=[on|off] kernel parameter what value we get with clock_getres(). -- blue skies, Martin. "Reality continues to ruin my life." - Calvin.
