mirror of
https://github.com/jart/cosmopolitan.git
synced 2025-02-07 15:03:34 +00:00
2f48a02b44
Recursive mutexes now go as fast as normal mutexes. The tradeoff is they are no longer safe to use in signal handlers. However you can still have signal safe mutexes if you set your mutex to both recursive and pshared. You can also make functions that use recursive mutexes signal safe using sigprocmask to ensure recursion doesn't happen due to any signal handler The impact of this change is that, on Windows, many functions which edit the file descriptor table rely on recursive mutexes, e.g. open(). If you develop your app so it uses pread() and pwrite() then your app should go very fast when performing a heavily multithreaded and contended workload For example, when scaling to 40+ cores, *NSYNC mutexes can go as much as 1000x faster (in CPU time) than the naive recursive lock implementation. Now recursive will use *NSYNC under the hood when it's possible to do so
86 lines
1.8 KiB
C
86 lines
1.8 KiB
C
#include <pthread.h>
|
|
#include <signal.h>
|
|
#include <stdatomic.h>
|
|
#include <stdbool.h>
|
|
#include <stdlib.h>
|
|
#include <unistd.h>
|
|
|
|
// tests that recursive mutexes are implemented atomically
|
|
//
|
|
// glibc fails this test
|
|
// musl passes this test
|
|
// cosmo only guarantees this in process shared mode
|
|
|
|
atomic_bool done;
|
|
atomic_bool ready;
|
|
pthread_mutex_t lock;
|
|
|
|
void hand(int sig) {
|
|
if (pthread_mutex_lock(&lock))
|
|
_Exit(50);
|
|
if (pthread_mutex_unlock(&lock))
|
|
_Exit(51);
|
|
}
|
|
|
|
void* work(void* arg) {
|
|
ready = true;
|
|
while (!done) {
|
|
if (pthread_mutex_lock(&lock))
|
|
_Exit(60);
|
|
if (pthread_mutex_unlock(&lock))
|
|
_Exit(61);
|
|
}
|
|
return 0;
|
|
}
|
|
|
|
int main() {
|
|
|
|
struct sigaction sa;
|
|
sa.sa_handler = hand;
|
|
sa.sa_flags = SA_NODEFER;
|
|
sigemptyset(&sa.sa_mask);
|
|
if (sigaction(SIGUSR1, &sa, 0))
|
|
_Exit(1);
|
|
|
|
pthread_mutexattr_t attr;
|
|
if (pthread_mutexattr_init(&attr))
|
|
_Exit(2);
|
|
if (pthread_mutexattr_settype(&attr, PTHREAD_MUTEX_RECURSIVE))
|
|
_Exit(3);
|
|
if (pthread_mutexattr_setpshared(&attr, PTHREAD_PROCESS_SHARED))
|
|
_Exit(3);
|
|
if (pthread_mutex_init(&lock, &attr))
|
|
_Exit(4);
|
|
if (pthread_mutexattr_destroy(&attr))
|
|
_Exit(5);
|
|
|
|
pthread_t th;
|
|
pthread_attr_t tattr;
|
|
if (pthread_attr_init(&tattr))
|
|
_Exit(6);
|
|
if (pthread_attr_setstacksize(&tattr, 8 * 1024 * 1024))
|
|
_Exit(7);
|
|
if (pthread_attr_setguardsize(&tattr, 64 * 1024))
|
|
_Exit(8);
|
|
if (pthread_create(&th, &tattr, work, 0))
|
|
_Exit(9);
|
|
if (pthread_attr_destroy(&tattr))
|
|
_Exit(10);
|
|
for (;;)
|
|
if (ready)
|
|
break;
|
|
|
|
for (int i = 0; i < 100; ++i) {
|
|
if (pthread_kill(th, SIGUSR1))
|
|
_Exit(11);
|
|
if (pthread_kill(th, SIGUSR1))
|
|
_Exit(12);
|
|
usleep(1);
|
|
}
|
|
|
|
done = true;
|
|
if (pthread_join(th, 0))
|
|
_Exit(13);
|
|
if (pthread_mutex_destroy(&lock))
|
|
_Exit(14);
|
|
}
|