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Introduce pthread_condattr_setclock()

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This is one of the few POSIX APIs that was missing. It lets you choose a
monotonic clock for your condition variables. This might improve perf on
some platforms. It might also grant more flexibility with NTP configs. I
know Qt is one project that believes it needs this. To introduce this, I
needed to change some the *NSYNC APIs, to support passing a clock param.
There's also new benchmarks, demonstrating Cosmopolitan's supremacy over
many libc implementations when it comes to mutex performance. Cygwin has
an alarmingly bad pthread_mutex_t implementation. It is so bad that they
would have been significantly better off if they'd used naive spinlocks.
This commit is contained in:
Justine Tunney 2024-09-02 23:37:50 -07:00
parent 79516bf08e
commit 3c61a541bd
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GPG key ID: BE714B4575D6E328
55 changed files with 449 additions and 155 deletions
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32
libc/calls/clock_gettime.c
View file

@ -24,6 +24,7 @@
#include "libc/intrin/describeflags.h"
#include "libc/intrin/strace.h"
#include "libc/runtime/syslib.internal.h"
#include "libc/sysv/consts/clock.h"
#ifdef __aarch64__
#define CGT_VDSO __vdsosym("LINUX_2.6.39", "__kernel_clock_gettime")
@ -58,14 +59,43 @@ static int __clock_gettime_init(int clockid, struct timespec *ts) {
return cgt(clockid, ts);
}
static int clock_gettime_impl(int clock, struct timespec *ts) {
int rc;
if (!IsLinux())
return __clock_gettime(clock, ts);
TryAgain:
// Ensure fallback for old Linux sticks.
if (clock == 4 /* CLOCK_MONOTONIC_RAW */)
clock = CLOCK_MONOTONIC_RAW;
// Call appropriate implementation.
rc = __clock_gettime(clock, ts);
// CLOCK_MONOTONIC_RAW is Linux 2.6.28+ so not available on RHEL5
if (rc == -EINVAL && clock == 4 /* CLOCK_MONOTONIC_RAW */) {
CLOCK_MONOTONIC_RAW = CLOCK_MONOTONIC;
CLOCK_MONOTONIC_RAW_APPROX = CLOCK_MONOTONIC;
goto TryAgain;
}
return rc;
}
/**
* Returns nanosecond time.
*
* @param clock supports the following values across OSes:
* - `CLOCK_REALTIME`
* - `CLOCK_MONOTONIC`
* - `CLOCK_MONOTONIC_RAW`
* - `CLOCK_MONOTONIC_RAW_APPROX`
* - `CLOCK_REALTIME_FAST`
* - `CLOCK_REALTIME_COARSE`
* - `CLOCK_REALTIME_PRECISE`
* - `CLOCK_MONOTONIC_FAST`
* - `CLOCK_MONOTONIC_COARSE`
* - `CLOCK_MONOTONIC_PRECISE`
* - `CLOCK_THREAD_CPUTIME_ID`
* - `CLOCK_PROCESS_CPUTIME_ID`
* @param ts is where the result is stored (or null to do clock check)
@ -80,7 +110,7 @@ static int __clock_gettime_init(int clockid, struct timespec *ts) {
*/
int clock_gettime(int clock, struct timespec *ts) {
// threads on win32 stacks call this so we can't asan check *ts
int rc = __clock_gettime(clock, ts);
int rc = clock_gettime_impl(clock, ts);
if (rc) {
errno = -rc;
rc = -1;