Re: [PATCH] sparc64: vdso: Flush the D-cache after updating the time data

[Imre Kaloz]

On Thu, 17 Sep 2026 10:25:47 +0200
Stian Halseth <stian@xxxxxx> wrote:

> On a Sun Fire V240 (UltraSPARC IIIi, clocksource stick) this makes
> clock_gettime(CLOCK_MONOTONIC) via the vDSO wrong for most calls on
> the tick CPU, by multiples of the 10 ms tick and up to a second, in
> about half of all processes: those that drew the other colour at
> exec.

Hi Stian,

Confirmed on a Sun Ultra 45 (UltraSPARC IIIi, SMP). The unpatched
kernel's vDSO clock_gettime() went stale on 3 out of 3 boots, up to
85% of CLOCK_MONOTONIC/CLOCK_REALTIME reads on the affected CPU, with
a lag up to 1492 ms. A kernel carrying this patch showed 0% stale
reads on 3 out of 3 boots.

Tested-by: Imre Kaloz <kaloz@xxxxxxxxxx>


Best,
Imre