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https://github.com/fluencelabs/musl
synced 2025-06-02 01:21:34 +00:00
4750cf4202
i did some testing trying to switch malloc to use the new internal lock with priority inheritance, and my malloc contention test got 20-100 times slower. if priority inheritance futexes are this slow, it's simply too high a price to pay for avoiding priority inversion. maybe we can consider them somewhere down the road once the kernel folks get their act together on this (and perferably don't link it to glibc's inefficient lock API)... as such, i've switch __lock to use malloc's implementation of lightweight locks, and updated all the users of the code to use an array with a waiter count for their locks. this should give optimal performance in the vast majority of cases, and it's simple. malloc is still using its own internal copy of the lock code because it seems to yield measurably better performance with -O3 when it's inlined (20% or more difference in the contention stress test).
49 lines
911 B
C
49 lines
911 B
C
#include <pthread.h>
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#include "libc.h"
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static struct atfork_funcs {
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void (*prepare)(void);
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void (*parent)(void);
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void (*child)(void);
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struct atfork_funcs *prev, *next;
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} *funcs;
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static int lock[2];
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void __fork_handler(int who)
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{
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struct atfork_funcs *p;
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if (!funcs) return;
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if (who < 0) {
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LOCK(lock);
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for (p=funcs; p; p = p->next) {
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if (p->prepare) p->prepare();
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funcs = p;
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}
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} else {
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for (p=funcs; p; p = p->prev) {
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if (!who && p->parent) p->parent();
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else if (who && p->child) p->child();
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funcs = p;
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}
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UNLOCK(lock);
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}
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}
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int pthread_atfork(void (*prepare)(void), void (*parent)(void), void (*child)(void))
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{
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struct atfork_funcs *new = malloc(sizeof *new);
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if (!new) return -1;
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LOCK(lock);
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new->next = funcs;
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new->prev = 0;
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new->prepare = prepare;
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new->parent = parent;
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new->child = child;
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if (funcs) funcs->prev = new;
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funcs = new;
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UNLOCK(lock);
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return 0;
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}
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