Date: Wed, 9 May 2012 20:15:26 +0000 (UTC) From: jb <jb.1234abcd@gmail.com> To: freebsd-questions@freebsd.org Subject: Re: Questions on adaptive mutexes and trylock Message-ID: <loom.20120509T213539-939@post.gmane.org> References: <4FAA8B8E.2070506@marcuscom.com>
next in thread | previous in thread | raw e-mail | index | archive | help
Joe Marcus Clarke <marcus <at> marcuscom.com> writes:
>
> The newest GLib (as well as PHP APC) is starting to use adaptive mutexes
> in their code. When a mutex type is set to adaptive and you try to call
> pthread_mutex_trylock() on it, you get back an EINVAL. Is this a bug,
> or should this really be happening (the code clearly indicates adaptive
> mutexes are not handled by trylock)?
Adaptive mutex is a combination of a mutex and a spinlock with adjusted
duration of spinning ("trylocking").
The primary purpose of a spinlock is to protect portions of the code that
implement other synchronization primitives such as a mutex, etc.
The pthread_mutex_trylock() attempts to acquire a lock on a mutex.
It follows it is proper to deny direct access to (adaptive) mutex by
pthread_mutex_trylock().
> I imagine Linux is not doing this since the code doesn't abort on Linux
> as it does on FreeBSD. Should we be silently allowing trylock to
> perform a no-op on adaptive mutexes, or should we be handling adaptive
> mutexes with trylock? Thanks.
I do not know why Linux handles it the way it does.
jb
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?loom.20120509T213539-939>