+1 from me, too On Mon, Oct 26, 2026 at 7:25 PM Tomek CEDRO <[email protected]> wrote:
> +1 here because: > * it solves old ambiguity. > * clearly conforms to POSIX testing / requirements. > * makes ticks, clocks, and time relation/calculation clear. > > Thank you Marco for bringing up this issue, presenting example > implementation, and nicely marking this change as breaking for > attention of possible users where this part is critical (i.e. PX4, > drones, rockets, automotive, motor control, etc) :-) > > -- > CeDeROM, SQ7MHZ, http://www.tomek.cedro.info > > On Mon, Oct 26, 2026 at 7:33 PM Marco C. <[email protected]> wrote: > > > > Hello all, > > > > This is the vote for the breaking change in > > https://github.com/apache/nuttx/pull/20947, as CONTRIBUTING.md 1.13 > > step 5 requires. The discussion is in the [DISCUSS] thread "Breaking > > change: make CLOCKS_PER_SEC 1000000": > > https://lists.apache.org/thread/bqxry570g9t63j63zmk4c5l82lybtx4s > > > > In that thread, Xiang asked for no Kconfig option ("always conform the > > spec or not change it at all"), so the change applies to all > > configurations. Alan agreed and suggested the next major release. > > Greg asked about the timer interrupt rate: the change does not change > > the timer or its interrupt rate (my reply in the thread). Nobody > > objected. > > > > The change: > > CLOCKS_PER_SEC is 1000000 and clock() returns microseconds (from > > clock_systime_timespec()). Today CLOCKS_PER_SEC is the system tick rate > > (1000000 / CONFIG_USEC_PER_TICK, 100 by default), and clock() returns > > ticks. The tick rate does not change: it is CLK_TCK and TICK_PER_SEC, > > times() still returns ticks, and sysconf(_SC_CLK_TCK) returns CLK_TCK. > > The resolution of clock() does not change: it still advances once per > > tick. clock_t is int64_t, so the value does not overflow. > > > > Reference: <time.h> and clock() in POSIX.1-2024 (XSI: CLOCKS_PER_SEC > > is one million): > > https://pubs.opengroup.org/onlinepubs/9799919799/basedefs/time.h.html > > https://pubs.opengroup.org/onlinepubs/9799919799/functions/clock.html > > Issue: https://github.com/apache/nuttx/issues/3516 > > > > Why it is necessary: > > - Programs written for POSIX systems expect 1000000, and the Open > > POSIX Test Suite checks it (conformance/interfaces/clock/2-1.c). > > - One macro had two meanings in NuttX: the unit of clock() and the > > tick rate. The 15 in-tree tickless configurations with > > CONFIG_USEC_PER_TICK=1 already have CLOCKS_PER_SEC = 1000000, so code > > that mixes the two meanings works there and fails elsewhere. > > > > Non-breaking alternative: a Kconfig option. Xiang explained in the > > thread why it is worse: the meaning of a standard macro would then > > depend on the configuration. > > > > The earlier steps are merged and do not change behaviour: > > - nuttx #20923: the kernel and libc use CLK_TCK for the tick rate and > > the tick counter for tick values; new CLOCK2TICK(), CLOCK2MSEC() and > > CLOCK2USEC() in <nuttx/clock.h> convert clock() values. > > - nuttx-apps #3904 (ftpc, cpuload, dhcpc, ping) and #3906 (bas). > > After them, no code in nuttx or nuttx-apps uses CLOCKS_PER_SEC as the > > tick rate or a clock() value as ticks. resmonitor and testsuites divide > > clock() differences by CLOCKS_PER_SEC and need no change. i8shark puts > > the raw clock() value into the ZEP timestamp field, which changes unit > > (it is not NTP time today either). > > > > Quick fix for out-of-tree code: > > - CLOCKS_PER_SEC used as "ticks per second" (for example to convert > > seconds into a timeout for wd_start() or nxsig_usleep()): use CLK_TCK > > or TICK_PER_SEC. > > - A clock() value used as ticks: use clock_systime_ticks() in the > > kernel, CLOCK2TICK(clock()) in user space, or convert a difference of > > clock() values with CLOCK2MSEC(), CLOCK2USEC() or CLOCKS_PER_SEC. > > - Code that divides clock() by CLOCKS_PER_SEC needs no change. > > - In protected and kernel builds clock() is a system call: build > > programs again with the new header. > > > > Tests: build and runtime logs on real hardware (RP2350, Cortex-M33, and > > ESP32-S3, Xtensa LX7) are in the PR, with ostest and a test of > > CLOCKS_PER_SEC, clock() and times() (fails on master, passes with the > > PR). The PR also has QEMU runs and builds of flat, protected and kernel > > configurations on arm64, rv64 and armv7-m. > > > > The vote is open for at least 72 hours. > > > > [ ] +1 Accept the change > > [ ] 0 No opinion > > [ ] -1 Reject the change, because... > > > > NuttX PMC members cast binding votes. The change needs at least 4 > > binding +1 votes and no binding -1 vote. > > > > My vote: +1 (non-binding) > > > > Regards, > > Marco Casaroli >
