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Make locks more reliable

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This change switches most of the core locks to be re-entrant, in order
to reduce the chance of deadlocking code that does, clever things with
asynchronous signal handlers. This change implements it it in pthreads
so we're one step closer to having a standardized threading primitives
This commit is contained in:
Justine Tunney 2022-06-11 01:59:26 -07:00
parent 5ea618f0af
commit c260345e06
35 changed files with 369 additions and 258 deletions
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21
libc/stdio/flockfile.c
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@ -16,30 +16,11 @@
│ TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR │
│ PERFORMANCE OF THIS SOFTWARE. │
╚─────────────────────────────────────────────────────────────────────────────*/
#include "libc/calls/calls.h"
#include "libc/intrin/cmpxchg.h"
#include "libc/intrin/lockcmpxchgp.h"
#include "libc/nexgen32e/threaded.h"
#include "libc/stdio/stdio.h"
/**
* Acquires reentrant lock on stdio object, blocking if needed.
*/
void flockfile(FILE *f) {
int me, owner;
unsigned tries;
if (__threaded) {
for (tries = 0, me = gettid();;) {
owner = 0;
if (_lockcmpxchgp(&f->lock, &owner, me) || owner == me) {
break;
}
if (++tries & 7) {
__builtin_ia32_pause();
} else {
sched_yield();
}
}
}
++f->reent;
pthread_mutex_lock(&f->lock);
}