From: Benjamin Herrenschmidt <benh@kernel.crashing.org>
To: Chirag Jog <chirag@linux.vnet.ibm.com>
Cc: linux-rt-users@vger.kernel.org,
Josh Triplett <josht@linux.vnet.ibm.com>,
Steven Rostedt <rostedt@goodmis.org>,
linuxppc-dev@ozlabs.org, Nivedita Singhvi <niv@us.ibm.com>,
"Timothy R. Chavez" <tim.chavez@linux.vnet.ibm.com>,
Thomas Gleixner <tglx@linutronix.de>,
paulmck@linux.vnet.ibm.com, linux.kernel@vger.kernel.org
Subject: Re: [PATCH][RT][PPC64] Fix preempt unsafe paths accessing per_cpu variables
Date: Fri, 18 Jul 2008 06:14:31 +1000 [thread overview]
Message-ID: <1216325671.7740.359.camel@pasglop> (raw)
In-Reply-To: <20080717125645.GN20277@linux.vnet.ibm.com>
> All these operations are done assuming that tlb_gather_mmu disables
> preemption and tlb_finish_mmu enables preemption again.
> This is not true for -rt.
> For x86, none of the code paths between tlb_gather_mmu and
> tlb_finish_mmu access any per_cpu variables.
> But this is not true for powerpc64 as we can see.
>
> One way could be to make tlb_gather_mmu disable preemption as it does
> in mainline but only for powerpc.
> Although i am not sure, if this is the right step ahead.
>
> I am attaching a patch below for the same.
> I have left out the tce bits, as they are fine.
>
> Note: I haven't extensively tested the patch
A better option is to make sure that a context switch does the right
thing, flushing the pending batch. I think that's already the case,
which means that your original patch may work, but that needs to
be double-checked and commented properly.
Cheers,
Ben.
WARNING: multiple messages have this Message-ID (diff)
From: Benjamin Herrenschmidt <benh@kernel.crashing.org>
To: Chirag Jog <chirag@linux.vnet.ibm.com>
Cc: linux.kernel@vger.kernel.org, linux-rt-users@vger.kernel.org,
linuxppc-dev@ozlabs.org, Josh Triplett <josht@linux.vnet.ibm.com>,
Steven Rostedt <rostedt@goodmis.org>,
Nivedita Singhvi <niv@us.ibm.com>,
"Timothy R. Chavez" <tim.chavez@linux.vnet.ibm.com>,
paulmck@linux.vnet.ibm.com, Thomas Gleixner <tglx@linutronix.de>
Subject: Re: [PATCH][RT][PPC64] Fix preempt unsafe paths accessing per_cpu variables
Date: Fri, 18 Jul 2008 06:14:31 +1000 [thread overview]
Message-ID: <1216325671.7740.359.camel@pasglop> (raw)
In-Reply-To: <20080717125645.GN20277@linux.vnet.ibm.com>
> All these operations are done assuming that tlb_gather_mmu disables
> preemption and tlb_finish_mmu enables preemption again.
> This is not true for -rt.
> For x86, none of the code paths between tlb_gather_mmu and
> tlb_finish_mmu access any per_cpu variables.
> But this is not true for powerpc64 as we can see.
>
> One way could be to make tlb_gather_mmu disable preemption as it does
> in mainline but only for powerpc.
> Although i am not sure, if this is the right step ahead.
>
> I am attaching a patch below for the same.
> I have left out the tce bits, as they are fine.
>
> Note: I haven't extensively tested the patch
A better option is to make sure that a context switch does the right
thing, flushing the pending batch. I think that's already the case,
which means that your original patch may work, but that needs to
be double-checked and commented properly.
Cheers,
Ben.
next prev parent reply other threads:[~2008-07-17 20:23 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-07-09 16:05 [PATCH][RT][PPC64] Fix preempt unsafe paths accessing per_cpu variables Chirag Jog
2008-07-09 16:05 ` Chirag Jog
2008-07-11 8:19 ` Sebastien Dugue
2008-07-11 8:19 ` Sebastien Dugue
2008-07-15 1:32 ` Benjamin Herrenschmidt
2008-07-15 1:32 ` Benjamin Herrenschmidt
2008-07-17 12:56 ` Chirag Jog
2008-07-17 12:56 ` Chirag Jog
2008-07-17 20:14 ` Benjamin Herrenschmidt [this message]
2008-07-17 20:14 ` Benjamin Herrenschmidt
2008-07-18 10:11 ` Chirag Jog
2008-07-18 10:11 ` Chirag Jog
2008-07-18 22:05 ` Benjamin Herrenschmidt
2008-07-18 22:05 ` Benjamin Herrenschmidt
2008-07-19 1:26 ` Steven Rostedt
2008-07-19 1:26 ` Steven Rostedt
2008-07-19 3:53 ` Benjamin Herrenschmidt
2008-07-19 3:53 ` Benjamin Herrenschmidt
2008-07-21 10:23 ` Chirag Jog
-- strict thread matches above, loose matches on Subject: below --
2008-07-09 15:33 Chirag Jog
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