Re: [PATCH 12/14] vdso/gettimeofday: Add support for auxiliary clocks

On Tue, Jul 01 2025 at 10:58, Thomas Weißschuh wrote:

+static __always_inline +bool do_aux(const struct vdso_time_data *vd, clockid_t clock, struct __kernel_timespec *ts) +{

• const struct vdso_clock *vc;
• u64 sec, ns;
• u32 seq;
• u8 idx;
• if (!IS_ENABLED(CONFIG_POSIX_AUX_CLOCKS))

• return false;
  

• idx = clock - CLOCK_AUX;
• vc = &vd->aux_clock_data[idx];
• do {

• /*
  

•  * Open coded function vdso_read_begin() to handle
  

•  * VDSO_CLOCK_TIMENS. See comment in do_hres().
  

•  */
  

• while ((seq = READ_ONCE(vc->seq)) & 1) {
  

• 	if (IS_ENABLED(CONFIG_TIME_NS) && vc->clock_mode == VDSO_CLOCKMODE_TIMENS) {
  

• 		vd = __arch_get_vdso_u_timens_data(vd);
  

• 		vc = &vd->aux_clock_data[idx];
  

• 		break;
  

This actually wants to be a continue because otherwise @seq contains the stale value from the initial read of the TIMENS page, which is 0x1. That's a pointless extra round through the below.

With continue it re-reads, but this time the actual value from the time data page and also takes an eventual odd value into account properly.

I fixed it up locally already.

Thanks,

tglx