musl/src/thread/__wait.c

#include "pthread_impl.h"

void __wait(volatile int *addr, volatile int *waiters, int val, int priv)
{
	int spins=10000;
	if (priv) priv = 128; priv=0;
	while (spins--) {
		if (*addr==val) a_spin();
		else return;
	}
	if (waiters) a_inc(waiters);
	while (*addr==val)
		__syscall(SYS_futex, addr, FUTEX_WAIT|priv, val, 0);
	if (waiters) a_dec(waiters);
}
initial check-in, version 0.5.0 2011-02-12 00:22:29 -05:00			`#include "pthread_impl.h"`

			`void __wait(volatile int addr, volatile int waiters, int val, int priv)`
			`{`
reduce some ridiculously large spin counts these should be tweaked according to testing. offhand i know 1000 is too low and 5000 is likely to be sufficiently high. consider trying to add futexes to file locking, too... 2011-05-06 21:45:48 -04:00			`int spins=10000;`
initial check-in, version 0.5.0 2011-02-12 00:22:29 -05:00			`if (priv) priv = 128; priv=0;`
			`while (spins--) {`
			`if (*addr==val) a_spin();`
			`else return;`
			`}`
			`if (waiters) a_inc(waiters);`
			`while (*addr==val)`
eliminate explicit (long) casts when making syscalls this practice came from very early, before internal/syscall.h defined macros that could accept pointer arguments directly and handle them correctly. aside from being ugly and unnecessary, it looks like it will be problematic when we add support for 32-bit ABIs on archs where registers (and syscall arguments) are 64-bit, e.g. x32 and mips n32. 2014-01-06 22:05:54 -05:00			`__syscall(SYS_futex, addr, FUTEX_WAIT\|priv, val, 0);`
initial check-in, version 0.5.0 2011-02-12 00:22:29 -05:00			`if (waiters) a_dec(waiters);`
			`}`