From: Benjamin Herrenschmidt <benh@kernel.crashing.org>
To: Paul Mackerras <paulus@samba.org>
Cc: linuxppc-dev list <linuxppc-dev@ozlabs.org>,
Anton Blanchard <anton@samba.org>,
linux-mm@kvack.org
Subject: Re: [RFC/PATCH] powerpc: tlb flush batch use lazy MMU mode
Date: Thu, 12 Apr 2007 11:35:26 +1000 [thread overview]
Message-ID: <1176341727.8061.112.camel@localhost.localdomain> (raw)
In-Reply-To: <1176188977.8061.48.camel@localhost.localdomain>
On Tue, 2007-04-10 at 17:09 +1000, Benjamin Herrenschmidt wrote:
> The current tlb flush code on powerpc 64 bits has a subtle race since we
> lost the page table lock due to the possible faulting in of new PTEs
> after a previous one has been removed but before the corresponding hash
> entry has been evicted, which can leads to all sort of fatal problems.
>
> This patch reworks the batch code completely. It doesn't use the mmu_gather
> stuff anymore. Instead, we use the lazy mmu hooks that were added by the
> paravirt code. They have the nice property that the enter/leave lazy mmu
> mode pair is always fully contained by the PTE lock for a given range
> of PTEs. Thus we can guarantee that all batches are flushed on a given
> CPU before it drops that lock.
.../...
Ran for a little while on a P5 partition with a few sdet runs and it
seems to be fine. You can apply :-)
Despite the bug being present in 2.6.21 (and earlier), I still think
however that this is .22 material, at least for now.
Ben.
WARNING: multiple messages have this Message-ID (diff)
From: Benjamin Herrenschmidt <benh@kernel.crashing.org>
To: Paul Mackerras <paulus@samba.org>
Cc: linuxppc-dev list <linuxppc-dev@ozlabs.org>,
Anton Blanchard <anton@samba.org>,
linux-mm@kvack.org
Subject: Re: [RFC/PATCH] powerpc: tlb flush batch use lazy MMU mode
Date: Thu, 12 Apr 2007 11:35:26 +1000 [thread overview]
Message-ID: <1176341727.8061.112.camel@localhost.localdomain> (raw)
In-Reply-To: <1176188977.8061.48.camel@localhost.localdomain>
On Tue, 2007-04-10 at 17:09 +1000, Benjamin Herrenschmidt wrote:
> The current tlb flush code on powerpc 64 bits has a subtle race since we
> lost the page table lock due to the possible faulting in of new PTEs
> after a previous one has been removed but before the corresponding hash
> entry has been evicted, which can leads to all sort of fatal problems.
>
> This patch reworks the batch code completely. It doesn't use the mmu_gather
> stuff anymore. Instead, we use the lazy mmu hooks that were added by the
> paravirt code. They have the nice property that the enter/leave lazy mmu
> mode pair is always fully contained by the PTE lock for a given range
> of PTEs. Thus we can guarantee that all batches are flushed on a given
> CPU before it drops that lock.
.../...
Ran for a little while on a P5 partition with a few sdet runs and it
seems to be fine. You can apply :-)
Despite the bug being present in 2.6.21 (and earlier), I still think
however that this is .22 material, at least for now.
Ben.
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next prev parent reply other threads:[~2007-04-12 1:35 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-04-10 7:09 [RFC/PATCH] powerpc: tlb flush batch use lazy MMU mode Benjamin Herrenschmidt
2007-04-10 7:09 ` Benjamin Herrenschmidt
2007-04-12 1:35 ` Benjamin Herrenschmidt [this message]
2007-04-12 1:35 ` Benjamin Herrenschmidt
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