Re: [PATCH 1/3] acpi: add real mutex function calls

Daniel Walker
2008-07-21T13:56:18Z

On Mon, 2008-07-21 at 09:51 +0800, Zhao Yakui wrote:
> On Sat, 2008-07-19 at 11:16 -0700, Daniel Walker wrote:
> > Instead of re-using semaphores for the mutex operation, I've
> > added usage of the kernel mutex for the os mutex implementation.
> >
> What is the advantage that the kernel mutex is used for the ACPI mutex
> implementation instead of using semaphore?
> And it seems that too much ACPICA source code is touched.

In general you would want to use a mutex whenever your using mutex-like
semantics. If I see a mutex used in code then I have a pretty good idea
the locking is sane.. As Peter mentioned , you also get lockdep which
helps to find lots of different locking problems.

You can also look at Documentation/mutex-design.txt which has a fairly
big list of benefits over the semaphore. (tho when that was written the
semaphore implementation was different.)

Daniel