libbb: make msleep() result in only one syscall instead of looping
function old new delta
msleep 45 52 +7
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
diff --git a/libbb/bb_do_delay.c b/libbb/bb_do_delay.c
index 3dbf032..9a84fa2 100644
--- a/libbb/bb_do_delay.c
+++ b/libbb/bb_do_delay.c
@@ -36,6 +36,7 @@
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 @@
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
}