Date: Tue, 09 Jun 2015 16:04:40 -0700 From: "Russell L. Carter" <rcarter@pinyon.org> To: freebsd-hackers@freebsd.org Subject: umtx_lock and friends Message-ID: <55777108.5020206@pinyon.org>
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Hi,
I'm investigating what the most lightweight inter-process mutex
technique on FreeBSD and have been looking at the
infrastructure in /usr/include/sys/umtx.h
However, my simple test program fails to link:
#include <stdio.h>
#include <sys/types.h>
#include <machine/atomic.h>
#include <errno.h>
#include <sys/umtx.h>
int main(int, char **)
{
printf("Testing...");
struct umtx m;
umtx_init(&m);
u_long id=5;
umtx_lock(&m, id);
umtx_unlock(&m, id);
printf("Test done.");
return 0;
}
produces the following:
tester.cpp:(.text+0x36): undefined reference to `_umtx_lock(umtx*)'
tester.cpp:(.text+0x5f): undefined reference to `_umtx_unlock(umtx*)'
I've tried linking against a variety of suspects in /usr/lib but
no luck.
go-lang uses _umtx_op but they make the syscall directly via asm,
it seems.
I can build an inter-process mutex over semaphores but the umtx
stuff looks perfect if I can get it to work.
Thanks,
Russell
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