Re: [RFC, PATCH] locks: remove posix deadlock detection

Jiri Kosina
2007-10-28T22:56:48Z

On Sun, 28 Oct 2007, Matthew Wilcox wrote:

> Bzzt. You get a false deadlock with multiple threads like so:
> Thread A of task B takes lock 1
> Thread C of task D takes lock 2
> Thread C of task D blocks on lock 1
> Thread E of task B blocks on lock 2

A potential for deadlock occurs if a process controlling a locked
region is put to sleep by attempting to lock another process'
locked region. If the system detects that sleeping until a locked
region is unlocked would cause a deadlock, fcntl() shall fail with
an [EDEADLK] error.

This is what POSIX says [1], even after being modified with respect to
POSIX Threads Extension, right?

So it doesn't deal with threads at all, just processess are taken into
account. Probably for a reason :)

[1] http://www.opengroup.org/onlinepubs/009695399/functions/fcntl.html

--
Jiri Kosina