The branch main has been updated by mav: URL: https://cgit.FreeBSD.org/src/commit/?id=56070dd2e4df70e4de2a10c7ace684ceb8b0f0bd
commit 56070dd2e4df70e4de2a10c7ace684ceb8b0f0bd Author: Alexander Motin <[email protected]> AuthorDate: 2022-03-04 03:03:09 +0000 Commit: Alexander Motin <[email protected]> CommitDate: 2022-03-04 03:03:09 +0000 Improve timeout precision of pthread_cond_timedwait(). This code was not touched when all other user-space sleep functions were switched to sbintime_t and decoupled from hardclock. When it is possible, convert supplied times into sbinuptime to supply directly to msleep_sbt() with C_ABSOLUTE. This provides the timeout resolution of few microseconds instead of 2 milliseconds, plus avoids few clock reads and conversions. Reviewed by: vangyzen MFC after: 1 month Differential Revision: https://reviews.freebsd.org/D34163 --- sys/kern/kern_umtx.c | 130 ++++++++++++++++++++++++++++++++------------------- 1 file changed, 82 insertions(+), 48 deletions(-) diff --git a/sys/kern/kern_umtx.c b/sys/kern/kern_umtx.c index 97673ed77e11..b864e6fe9e49 100644 --- a/sys/kern/kern_umtx.c +++ b/sys/kern/kern_umtx.c @@ -175,8 +175,6 @@ static SYSCTL_NODE(_debug_umtx, OID_AUTO, chains, CTLFLAG_RD | CTLFLAG_MPSAFE, 0 static inline void umtx_abs_timeout_init2(struct umtx_abs_timeout *timo, const struct _umtx_time *umtxtime); -static int umtx_abs_timeout_gethz(struct umtx_abs_timeout *timo); -static inline void umtx_abs_timeout_update(struct umtx_abs_timeout *timo); static void umtx_shm_init(void); static void umtxq_sysinit(void *); @@ -683,20 +681,14 @@ umtx_abs_timeout_init(struct umtx_abs_timeout *timo, int clockid, timo->clockid = clockid; if (!absolute) { timo->is_abs_real = false; - umtx_abs_timeout_update(timo); + kern_clock_gettime(curthread, timo->clockid, &timo->cur); timespecadd(&timo->cur, timeout, &timo->end); } else { timo->end = *timeout; timo->is_abs_real = clockid == CLOCK_REALTIME || clockid == CLOCK_REALTIME_FAST || - clockid == CLOCK_REALTIME_PRECISE; - /* - * If is_abs_real, umtxq_sleep will read the clock - * after setting td_rtcgen; otherwise, read it here. - */ - if (!timo->is_abs_real) { - umtx_abs_timeout_update(timo); - } + clockid == CLOCK_REALTIME_PRECISE || + clockid == CLOCK_SECOND; } } @@ -709,22 +701,71 @@ umtx_abs_timeout_init2(struct umtx_abs_timeout *timo, (umtxtime->_flags & UMTX_ABSTIME) != 0, &umtxtime->_timeout); } -static void -umtx_abs_timeout_update(struct umtx_abs_timeout *timo) -{ - - kern_clock_gettime(curthread, timo->clockid, &timo->cur); -} - static int -umtx_abs_timeout_gethz(struct umtx_abs_timeout *timo) +umtx_abs_timeout_getsbt(struct umtx_abs_timeout *timo, sbintime_t *sbt, + int *flags) { + struct bintime bt, bbt; struct timespec tts; - if (timespeccmp(&timo->end, &timo->cur, <=)) - return (-1); - timespecsub(&timo->end, &timo->cur, &tts); - return (tstohz(&tts)); + switch (timo->clockid) { + + /* Clocks that can be converted into absolute time. */ + case CLOCK_REALTIME: + case CLOCK_REALTIME_PRECISE: + case CLOCK_REALTIME_FAST: + case CLOCK_MONOTONIC: + case CLOCK_MONOTONIC_PRECISE: + case CLOCK_MONOTONIC_FAST: + case CLOCK_UPTIME: + case CLOCK_UPTIME_PRECISE: + case CLOCK_UPTIME_FAST: + case CLOCK_SECOND: + timespec2bintime(&timo->end, &bt); + switch (timo->clockid) { + case CLOCK_REALTIME: + case CLOCK_REALTIME_PRECISE: + case CLOCK_REALTIME_FAST: + case CLOCK_SECOND: + getboottimebin(&bbt); + bintime_sub(&bt, &bbt); + break; + } + if (bt.sec < 0) + return (ETIMEDOUT); + if (bt.sec >= (SBT_MAX >> 32)) { + *sbt = 0; + *flags = 0; + return (0); + } + *sbt = bttosbt(bt); + switch (timo->clockid) { + case CLOCK_REALTIME_FAST: + case CLOCK_MONOTONIC_FAST: + case CLOCK_UPTIME_FAST: + *sbt += tc_tick_sbt; + break; + case CLOCK_SECOND: + *sbt += SBT_1S; + break; + } + *flags = C_ABSOLUTE; + return (0); + + /* Clocks that has to be periodically polled. */ + case CLOCK_VIRTUAL: + case CLOCK_PROF: + case CLOCK_THREAD_CPUTIME_ID: + case CLOCK_PROCESS_CPUTIME_ID: + default: + kern_clock_gettime(curthread, timo->clockid, &timo->cur); + if (timespeccmp(&timo->end, &timo->cur, <=)) + return (ETIMEDOUT); + timespecsub(&timo->end, &timo->cur, &tts); + *sbt = tick_sbt * tstohz(&tts); + *flags = C_HARDCLOCK; + return (0); + } } static uint32_t @@ -746,15 +787,11 @@ umtx_unlock_val(uint32_t flags, bool rb) */ int umtxq_sleep(struct umtx_q *uq, const char *wmesg, - struct umtx_abs_timeout *abstime) + struct umtx_abs_timeout *timo) { struct umtxq_chain *uc; - int error, timo; - - if (abstime != NULL && abstime->is_abs_real) { - curthread->td_rtcgen = atomic_load_acq_int(&rtc_generation); - umtx_abs_timeout_update(abstime); - } + sbintime_t sbt = 0; + int error, flags = 0; uc = umtxq_getchain(&uq->uq_key); UMTXQ_LOCKED_ASSERT(uc); @@ -763,26 +800,22 @@ umtxq_sleep(struct umtx_q *uq, const char *wmesg, error = 0; break; } - if (abstime != NULL) { - timo = umtx_abs_timeout_gethz(abstime); - if (timo < 0) { - error = ETIMEDOUT; - break; - } - } else - timo = 0; - error = msleep(uq, &uc->uc_lock, PCATCH | PDROP, wmesg, timo); - if (error == EINTR || error == ERESTART) { - umtxq_lock(&uq->uq_key); - break; - } - if (abstime != NULL) { - if (abstime->is_abs_real) + if (timo != NULL) { + if (timo->is_abs_real) curthread->td_rtcgen = atomic_load_acq_int(&rtc_generation); - umtx_abs_timeout_update(abstime); + error = umtx_abs_timeout_getsbt(timo, &sbt, &flags); + if (error != 0) + break; + } + error = msleep_sbt(uq, &uc->uc_lock, PCATCH, wmesg, + sbt, 0, flags); + if (error == EINTR || error == ERESTART) + break; + if (error == EWOULDBLOCK && (flags & C_ABSOLUTE) != 0) { + error = ETIMEDOUT; + break; } - umtxq_lock(&uq->uq_key); } curthread->td_rtcgen = 0; @@ -3652,7 +3685,8 @@ again: if (error == ERESTART) error = EINTR; if (error == EINTR) { - umtx_abs_timeout_update(&timo); + kern_clock_gettime(curthread, timo.clockid, + &timo.cur); timespecsub(&timo.end, &timo.cur, &timeout->_timeout); }
