linux-kernel - Re: [BUG on PREEMPT_RT, 2.6.23.1-rt5] in rt-mutex code and signals

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Message-ID: <3efb10970711190455n5e635823t40a320c4b444fa57@mail.gmail.com>
Date:	Mon, 19 Nov 2007 13:55:45 +0100
From:	"Remy Bohmer" <linux@...mer.net>
To:	"Steven Rostedt" <rostedt@...dmis.org>
Cc:	"Ingo Molnar" <mingo@...e.hu>,
	"Thomas Gleixner" <tglx@...utronix.de>,
	RT <linux-rt-users@...r.kernel.org>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	"Daniel Walker" <dwalker@...sta.com>
Subject: Re: [BUG on PREEMPT_RT, 2.6.23.1-rt5] in rt-mutex code and signals

Hello Steven,

> > OK, I wont be able to work on this this weekend, but I'll try to get to it
> > on Monday.  A better example to show the bug you are looking for is simply
> > create a mutex and create a thread that grabs that mutex and goes to
> > sleep. Have your driver read grab that mutex with
> > mutex_lock_interruptible. And if the signal code is broken with this, then
> > you definitely got a point that the inerruptible code is broken.

I removed the 'struct semaphore' completely from my driver, using real
mutexes now instead, replace the signalling semaphores by 'struct
completion' mechanisms and got rid of the possible race I saw with the
completions in a different way, and now the problem is completely
gone!

Posix Signals work properly now (no OOPS anymore), so the problem was
likely related to the way I used the 'struct semaphore' types, which
is thus different compared to the non-RT kernel and therefor quite
confusing.

So, thank you (and Daniel) for pointing me into the right direction.

Now lets get rid of the 'struct semaphore' completely in the kernel :-))

Kind Regards,

Remy Bohmer
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