linux-kernel - Re: [ANNOUNCE] mdb-2.6.27-rc2-ia32-08-07-08.patch

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Message-ID: <17159.166.70.238.44.1218131541.squirrel@webmail.wolfmountaingroup.com>
Date:	Thu, 7 Aug 2008 11:52:21 -0600 (MDT)
From:	jmerkey@...fmountaingroup.com
To:	"Stefan Richter" <stefanr@...6.in-berlin.de>
Cc:	jmerkey@...fmountaingroup.com, linux-kernel@...r.kernel.org
Subject: Re: [ANNOUNCE] mdb-2.6.27-rc2-ia32-08-07-08.patch

> jmerkey@...fmountaingroup.com wrote:
>>> jmerkey@...fmountaingroup.com wrote:
>>>> rspin locks are for these types of cases -- so if I fault on the same
>>>> processor I took the lock on it just bumps a counter -- yes, it is
>>>> atomic
>>>> and SMP safe to do it this way.
>>> Only if all contexts which take rlocks are not preemptible.
> [...]
>> check mdb-main.c -- I disable preemption before rspin_lock is attempted.
>> Since the only processor which sets the proc number does do inside the
>> spin lock, and the other processors only read it, unless memory is
>> corrupted or the machine is severely broken, its SMP safe to this.
>
> Then it is recommendable that you document the call context requirements
> at the functions.  And you can and IMO should drop the _irq_save and
> _irq_restore from the spinlock accessors in the rlock accessors.  And
> drop the volatile qualifier of the rlock accessor argument while you are
> at it.
>
> I see that you are calling save_flags/ restore_flags in
> mdb-main.c::mdb().  These are marked as deprecated.  Would
> local_irq_save/ local_irq_restore be correct at these places?


You have sharp eyes.  Yes, you are correct.  added to the list of
corrections.

Jeff

> --
> Stefan Richter
> -=====-==--- =--- --===
> http://arcgraph.de/sr/
>


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