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

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function                                             old     new   delta
msleep                                                45      52      +7

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
This commit is contained in:
Denys Vlasenko 2020-12-11 16:48:47 +01:00
parent 56ee576507
commit 030fe31760
3 changed files with 21 additions and 4 deletions
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18
libbb/bb_do_delay.c
View File

@ -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
}

1
libbb/platform.c
View File

@ -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;

6
networking/ifupdown.c
View File

@ -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);