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List:       uclinux-dev
Subject:    Re: [uClinux-dev] patch for semaphore of pthread lib
From:       Mike Frysinger <vapier () gentoo ! org>
Date:       2006-10-26 14:28:20
Message-ID: 200610261028.23974.vapier () gentoo ! org
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On Thursday 26 October 2006 04:40, Falk Brettschneider wrote:
> Mike Frysinger <vapier@gentoo.org> wrote:
> > On Wednesday 25 October 2006 16:50, Falk Brettschneider wrote:
> > > 1) I replaced all occurrences of the internally used helper mutex
> > > __sem_lock with local_[dis|en]able_irq() in semaphore.c
> >
> > that'll never fly in general ... irq control is the domain of
> > kernel space and no where else
>
> one solution to fix thread priority inversion is to make the problematic
> code atomic. The only alternative to a mutex is to use IRQ-disabling to let
> it be atomic also. Well, the pthread lib is not part of the kernel, but in
> my opinion lowlevel thread management actually sounds much like a kernel
> job. Do you have an idea how semaphores can be IRQ-safe?

semaphores are atomic ... regardless, you dont do IRQ handling in userspace, 
end of story
-mike

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