Messages in this thread | | | Subject | Re: [PATCH 2/3] x86/vdso: Rearrange do_hres() to improve code generation | From | Andy Lutomirski <> | Date | Fri, 5 Oct 2018 06:05:19 -0700 |
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> On Oct 4, 2018, at 11:00 PM, Thomas Gleixner <tglx@linutronix.de> wrote: > >> On Thu, 4 Oct 2018, Andy Lutomirski wrote: >> index 18c8a78d1ec9..419de7552c2f 100644 >> --- a/arch/x86/entry/vdso/vclock_gettime.c >> +++ b/arch/x86/entry/vdso/vclock_gettime.c >> @@ -147,10 +147,9 @@ notrace static int do_hres(clockid_t clk, struct timespec *ts) >> >> do { >> seq = gtod_read_begin(gtod); >> - ts->tv_sec = base->sec; >> + cycles = vgetcyc(gtod->vclock_mode); >> ns = base->nsec; >> last = gtod->cycle_last; >> - cycles = vgetcyc(gtod->vclock_mode); >> if (unlikely((s64)cycles < 0)) >> return vdso_fallback_gettime(clk, ts); >> if (cycles > last) >> @@ -158,7 +157,7 @@ notrace static int do_hres(clockid_t clk, struct timespec *ts) >> ns >>= gtod->shift; >> } while (unlikely(gtod_read_retry(gtod, seq))); >> >> - ts->tv_sec += __iter_div_u64_rem(ns, NSEC_PER_SEC, &ns); >> + ts->tv_sec = base->sec + __iter_div_u64_rem(ns, NSEC_PER_SEC, &ns); > > You cannot access base->sec outside of the seqcount protected region. It > might have been incremented by now and you'll get a time jump by a full > second.
Duh. Let me try this again.
> > Thanks, > > tglx > >
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