From 030fe31760169783537162b83af89e551bf120f6 Mon Sep 17 00:00:00 2001 From: Denys Vlasenko Date: Fri, 11 Dec 2020 16:48:47 +0100 Subject: libbb: make msleep() result in only one syscall instead of looping function old new delta msleep 45 52 +7 Signed-off-by: Denys Vlasenko --- libbb/bb_do_delay.c | 18 ++++++++++++++++++ libbb/platform.c | 1 - networking/ifupdown.c | 6 +++--- 3 files changed, 21 insertions(+), 4 deletions(-) diff --git a/libbb/bb_do_delay.c b/libbb/bb_do_delay.c index 3dbf032db..9a84fa24b 100644 --- a/libbb/bb_do_delay.c +++ b/libbb/bb_do_delay.c @@ -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 } diff --git a/libbb/platform.c b/libbb/platform.c index d2b263a6d..329b0237e 100644 --- a/libbb/platform.c +++ b/libbb/platform.c @@ -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; diff --git a/networking/ifupdown.c b/networking/ifupdown.c index 60ceb5a1f..fedf05aaf 100644 --- a/networking/ifupdown.c +++ b/networking/ifupdown.c @@ -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); -- cgit v1.2.3