[Patch] C1X threading support
Poul-Henning Kamp
phk at phk.freebsd.dk
Tue Dec 20 14:22:01 UTC 2011
In message <201112200822.26369.jhb at freebsd.org>, John Baldwin writes:
>The reason I can think of why you might not specify
>this is if you want to support machines that have very limited support for
>atomic operations (e.g. only an exchange instruction or a single-bit test-and-
>set as opposed to a full-world test-and-set such as cmpxchg on x86 or cas on
>sparc).
There is no way this can be impossible on a platform which can
implement a mutex in the first place:
mtx_lock(l)
{
atomic_magic_lock(l->lock_field)
l->id = thread_id;
}
mtx_unlock(l)
{
assert(l->id == thread_id);
l->id = NULL;
atomic_magic_unlock(l->lock_field)
}
mtx_assert_held(l)
{
assert(l->lock-field != 0);
assert(l->id == thread_id);
}
--
Poul-Henning Kamp | UNIX since Zilog Zeus 3.20
phk at FreeBSD.ORG | TCP/IP since RFC 956
FreeBSD committer | BSD since 4.3-tahoe
Never attribute to malice what can adequately be explained by incompetence.
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