From: Siraaj Khandkar Date: Sun, 15 Mar 2020 00:06:57 +0000 (-0400) Subject: Pushback on data producers X-Git-Url: https://git.xandkar.net/?p=khatus.git;a=commitdiff_plain;h=b7487ec5a6f62c0c57836fff6cbaa52b116f0831 Pushback on data producers by refusing to read the pipe more frequently than the interval. --- diff --git a/x5/bsdtimespec.h b/x5/bsdtimespec.h new file mode 100644 index 0000000..88ee778 --- /dev/null +++ b/x5/bsdtimespec.h @@ -0,0 +1,73 @@ +/* $OpenBSD: time.h,v 1.36 2016/09/12 19:41:20 guenther Exp $ */ +/* $NetBSD: time.h,v 1.18 1996/04/23 10:29:33 mycroft Exp $ */ + +/* + * Copyright (c) 1982, 1986, 1993 + * The Regents of the University of California. All rights reserved. + * + * Redistribution and use in source and binary forms, with or without + * modification, are permitted provided that the following conditions + * are met: + * 1. Redistributions of source code must retain the above copyright + * notice, this list of conditions and the following disclaimer. + * 2. Redistributions in binary form must reproduce the above copyright + * notice, this list of conditions and the following disclaimer in the + * documentation and/or other materials provided with the distribution. + * 3. Neither the name of the University nor the names of its contributors + * may be used to endorse or promote products derived from this software + * without specific prior written permission. + * + * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND + * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE + * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE + * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE + * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL + * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS + * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) + * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT + * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY + * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF + * SUCH DAMAGE. + * + * @(#)time.h 8.2 (Berkeley) 7/10/94 + */ + +/* Operations on timespecs. */ +#ifndef timespecclear +#define timespecclear(tsp) (tsp)->tv_sec = (tsp)->tv_nsec = 0 +#endif + +#ifndef timespecisset +#define timespecisset(tsp) ((tsp)->tv_sec || (tsp)->tv_nsec) +#endif + +#ifndef timespeccmp +#define timespeccmp(tsp, usp, cmp) \ + (((tsp)->tv_sec == (usp)->tv_sec) ? \ + ((tsp)->tv_nsec cmp (usp)->tv_nsec) : \ + ((tsp)->tv_sec cmp (usp)->tv_sec)) +#endif + +#ifndef timespecadd +#define timespecadd(tsp, usp, vsp) \ + do { \ + (vsp)->tv_sec = (tsp)->tv_sec + (usp)->tv_sec; \ + (vsp)->tv_nsec = (tsp)->tv_nsec + (usp)->tv_nsec; \ + if ((vsp)->tv_nsec >= 1000000000L) { \ + (vsp)->tv_sec++; \ + (vsp)->tv_nsec -= 1000000000L; \ + } \ + } while (0) +#endif + +#ifndef timespecsub +#define timespecsub(tsp, usp, vsp) \ + do { \ + (vsp)->tv_sec = (tsp)->tv_sec - (usp)->tv_sec; \ + (vsp)->tv_nsec = (tsp)->tv_nsec - (usp)->tv_nsec; \ + if ((vsp)->tv_nsec < 0) { \ + (vsp)->tv_sec--; \ + (vsp)->tv_nsec += 1000000000L; \ + } \ + } while (0) +#endif diff --git a/x5/khatus.c b/x5/khatus.c index 6ecb1e7..cc28cba 100644 --- a/x5/khatus.c +++ b/x5/khatus.c @@ -8,10 +8,13 @@ #include #include #include +#include #include #include +#include "bsdtimespec.h" + #define debug(args...) {fprintf(stderr, "[debug] " args);} #define info( args...) {fprintf(stderr, "[info] " args);} #define error(args...) {fprintf(stderr, "[error] " args);} @@ -307,7 +310,6 @@ fifo_read_all(Config *cfg, char *buf) struct stat st; FD_ZERO(&fds); - /* TODO: Check TTL */ for (Fifo *f = cfg->fifos; f; f = f->next) { /* TODO: Create the FIFO if it doesn't already exist. */ if (lstat(f->name, &st) < 0) { @@ -347,6 +349,29 @@ fifo_read_all(Config *cfg, char *buf) } } +void +snooze(struct timespec *t) +{ + struct timespec remainder; + int result; + + result = nanosleep(t, &remainder); + + if (result < 0) { + if (errno == EINTR) { + info( + "nanosleep interrupted. Remainder: " + "{ tv_sec = %ld, tv_nsec = %ld }", + remainder.tv_sec, remainder.tv_nsec); + /* No big deal if we occasionally sleep less, + * so not attempting to correct after an interruption. + */ + } else { + fatal("nanosleep: %s\n", strerror(errno)); + } + } +} + int main(int argc, char *argv[]) { @@ -360,12 +385,23 @@ main(int argc, char *argv[]) Config *cfg = &cfg0; Display *display = NULL; struct stat st; + struct timespec + t0, /* time stamp. before reading fifos */ + t1, /* time stamp. after reading fifos */ + ti, /* time interval desired (t1 - t0) */ + td, /* time interval measured (t1 - t0) */ + tc; /* time interval correction (ti - td) when td < ti */ argv0 = argv[0]; opts_parse(cfg, argc, argv); debug("argv0 = %s\n", argv0); config_print(cfg); + + /* TODO: Support interval < 1. i.e. implement timespec_of_float */ + ti.tv_sec = cfg->interval; + ti.tv_nsec = 0; + if (cfg->fifos == NULL) usage("No fifo specs were given!\n"); @@ -410,14 +446,15 @@ main(int argc, char *argv[]) if (cfg->output_to_x_root_window && !(display = XOpenDisplay(NULL))) fatal("XOpenDisplay failed with: %p\n", display); - /* TODO: nanosleep and nano time diff */ /* TODO: Handle signals */ for (;;) { - /* TODO: Check TTL and maybe blank-out */ + clock_gettime(CLOCK_MONOTONIC, &t0); // FIXME: check errors + /* TODO: Cache expiration. i.e. use the TTL */ /* TODO: How to trigger TTL check? On select? Alarm signal? */ /* TODO: Set timeout on fifo_read_all based on diff of last time of * fifo_read_all and desired time of next TTL check. - * */ + */ + /* TODO: How long to wait on IO? Max TTL? */ fifo_read_all(cfg, buf); if (cfg->output_to_x_root_window) { if (XStoreName(display, DefaultRootWindow(display), buf) < 0) @@ -427,6 +464,18 @@ main(int argc, char *argv[]) puts(buf); fflush(stdout); } + clock_gettime(CLOCK_MONOTONIC, &t1); // FIXME: check errors + timespecsub(&t1, &t0, &td); + debug("td {tv_sec = %ld, tv_nsec = %ld}\n", td.tv_sec, td.tv_nsec); + if (timespeccmp(&td, &ti, <)) { + /* Pushback on data producers by refusing to read the + * pipe more frequently than the interval. + */ + timespecsub(&ti, &td, &tc); + debug("snooze YES\n"); + snooze(&tc); + } else + debug("snooze NO\n"); } return EXIT_SUCCESS;