030fe3176

Denys Vlasenko

2020-12-11

SUCCESS Duration: 150s

Subject

libbb: make msleep() result in only one syscall instead of looping

No binary (build failed)

Architecture: x86_64-linux-gnu Compiler: gcc (Ubuntu 11.4.0-1ubuntu1~22.04.3) 11.4.0

—

(log yok)

libbb/bb_do_delay.c+18 -0

@@ -36,6 +36,7 @@ void FAST_FUNC sleep1(void)

	void FAST_FUNC msleep(unsigned ms)
	{
+	#if 0
	/* 1. usleep(n) is not guaranteed by standards to accept n >= 1000000
	* 2. multiplication in usleep(ms * 1000) can overflow if ms > 4294967
	* (sleep of ~71.5 minutes)
@@ -46,4 +47,21 @@ void FAST_FUNC msleep(unsigned ms)
	ms -= 500;
	}
	usleep(ms * 1000);
+	#else
+	//usleep is often implemented as a call to nanosleep.
+	//Simply do the same to implement msleep.
+	//it's marginally larger, but wakes your CPU less often:
+	//function old new delta
+	//msleep 45 52 +7
+	struct timespec ts;
+	ts.tv_sec = ms / 1000;
+	ts.tv_nsec = (ms % 1000) * 1000000;
+	/*
+	* If a signal has non-default handler, nanosleep returns early.
+	* Our version of msleep doesn't return early
+	* if interrupted by such signals:
+	*/
+	while (nanosleep(&ts, &ts) != 0)
+	continue;
+	#endif
	}

libbb/platform.c+0 -1

@@ -27,7 +27,6 @@ int FAST_FUNC usleep(unsigned usec)
	* If a signal has non-default handler, nanosleep returns early.
	* Our version of usleep doesn't return early
	* if interrupted by such signals:
-	*
	*/
	while (nanosleep(&ts, &ts) != 0)
	continue;

networking/ifupdown.c+3 -3

@@ -1357,15 +1357,15 @@ static FILE *open_new_state_file(void)
	IFSTATE_FILE_PATH".new");
	}
	/* Someone else created the .new file */
-	if (cnt > 30 * 1000) {
+	if (cnt > 30) {
	/* Waited for 30*30/2 = 450 milliseconds, still EEXIST.
	* Assuming a stale file, rewriting it.
	*/
	flags = (O_WRONLY \| O_CREAT \| O_TRUNC);
	continue;
	}
-	usleep(cnt);
-	cnt += 1000;
+	msleep(cnt);
+	cnt++;
	}

	return xfdopen_for_write(fd);