From: Ben Harris <bjh21@bjh21.me.uk>
Date: Fri, 23 Nov 2018 21:27:47 +0000 (+0000)
Subject: Take advantage of sigtimedwait().
X-Git-Url: https://www.chiark.greenend.org.uk/ucgi/~bjharris/git?a=commitdiff_plain;h=183ed928a18a8fa4c59f7705108f0a5efb7782ba;p=clunk.git

Take advantage of sigtimedwait().

This saves the need for two separate timers, since the sigtimedwait()
timeout can serve the purpose of the fallback timer.
---

diff --git a/clunk.c b/clunk.c
index 8fa0d19..7f10dc9 100644
--- a/clunk.c
+++ b/clunk.c
@@ -37,12 +37,7 @@ static char statebuf[10];
 
 static sigset_t signals_to_block, timing_signals;
 
-/*
- * The fallback timer protects us from occasions when CLOCK_REALTIME
- * goes backwards so our nice absolute clock_nanosleep() end up
- * sleeping far too long.
- */
-static timer_t main_timer, fallback_timer;
+static timer_t main_timer;
 
 static void
 dummy_out(bool state)
@@ -202,8 +197,6 @@ init(int argc, char **argv)
 		err(1, "sigprocmask");
 	if (timer_create(CLOCK_REALTIME, &sev, &main_timer) != 0)
 		err(1, "timer_create");
-	if (timer_create(CLOCK_MONOTONIC, &sev, &fallback_timer) != 0)
-		err(1, "timer_create");
 
 	if (clock_gettime(CLOCK_REALTIME, &ts) != 0)
 		err(1, "clock_gettime");
@@ -263,13 +256,10 @@ run()
 	struct itimerspec its_main = {
 		.it_interval = { .tv_sec = 0, .tv_nsec = 0}
 	};
-	const struct itimerspec its_fallback = {
-		.it_value    = { .tv_sec = 35, .tv_nsec = 0},
-		.it_interval = { .tv_sec = 0,  .tv_nsec = 0},
-	};
 	const struct itimerspec its_disarm = {
 		.it_value =  { .tv_sec = 0, .tv_nsec = 0 },
 	};
+	struct timespec const timeout = { .tv_sec = 31, .tv_nsec = 0 };
 	struct tm tm;
 	int tick;
 	sigset_t pending_signals;
@@ -302,22 +292,22 @@ run()
 		if (timer_settime(main_timer, TIMER_ABSTIME, &its_main, NULL)
 		    != 0)
 			err(1, "timer_settime (arm main)");
-		if (timer_settime(fallback_timer, 0, &its_fallback, NULL) != 0)
-			err(1, "timer_settime (arm fallback)");
-		errno = sigwait(&timing_signals, &signo);
-		if (errno != 0)
-			err(1, "sigwait");
-		if (timer_settime(main_timer, 0, &its_disarm, NULL) != 0)
-			err(1, "timer_settime (disarm)");
-		if (timer_settime(fallback_timer, 0, &its_disarm, NULL) != 0)
-			err(1, "timer_settime (disarm)");
-		/* Clear any pending SIGALRM */
-		if (sigpending(&pending_signals) == -1)
-			err(1, "sigpending");
-		if (sigismember(&pending_signals, SIGALRM)) {
-			errno = sigwait(&timing_signals, &signo);
-			if (errno != 0)
-				err(1, "sigwait");
+		if (sigtimedwait(&timing_signals, NULL, &timeout) == -1) {
+			if (errno != EAGAIN)
+				err(1, "sigtimedwait");
+			/* Fallback timeout expired. */
+			/* Disarm the main timer. */
+			if (timer_settime(main_timer, 0,
+					  &its_disarm, NULL) != 0)
+				err(1, "timer_settime (disarm)");
+			/* Clear any pending SIGALRM. */
+			if (sigpending(&pending_signals) == -1)
+				err(1, "sigpending");
+			if (sigismember(&pending_signals, SIGALRM)) {
+				errno = sigwait(&timing_signals, &signo);
+				if (errno != 0)
+					err(1, "sigwait");
+			}
 		}
 	}
 }