From: Michal Hocko <mhocko@kernel.org>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Yunsheng Lin <linyunsheng@huawei.com>,
catalin.marinas@arm.com, will@kernel.org, mingo@redhat.com,
bp@alien8.de, rth@twiddle.net, ink@jurassic.park.msu.ru,
mattst88@gmail.com, benh@kernel.crashing.org, paulus@samba.org,
mpe@ellerman.id.au, heiko.carstens@de.ibm.com, gor@linux.ibm.com,
borntraeger@de.ibm.com, ysato@users.sourceforge.jp,
dalias@libc.org, davem@davemloft.net, ralf@linux-mips.org,
paul.burton@mips.com, jhogan@kernel.org, jiaxun.yang@flygoat.com,
chenhc@lemote.com, akpm@linux-foundation.org, rppt@linux.ibm.com,
anshuman.khandual@arm.com, tglx@linutronix.de, cai@lca.pw,
robin.murphy@arm.com, linux-arm-kernel@lists.infradead.org,
linux-kernel@vger.kernel.org, hpa@zytor.com, x86@kernel.org,
dave.hansen@linux.intel.com, luto@kernel.org,
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jeffrey.t.kirsher@intel.com, linux-alpha@vger.kernel.org,
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linuxppc-dev@lists.ozlabs.org, linux-s390@vger.kernel.org,
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tbogendoerfer@suse.de, linux-mips@vger.kernel.org,
rafael@kernel.org, gregkh@linuxfoundation.org
Subject: Re: [PATCH v6] numa: make node_to_cpumask_map() NUMA_NO_NODE aware
Date: Mon, 23 Sep 2019 17:28:56 +0200 [thread overview]
Message-ID: <20190923152856.GB17206@dhcp22.suse.cz> (raw)
In-Reply-To: <20190923151519.GE2369@hirez.programming.kicks-ass.net>
On Mon 23-09-19 17:15:19, Peter Zijlstra wrote:
> On Tue, Sep 17, 2019 at 08:48:54PM +0800, Yunsheng Lin wrote:
> > When passing the return value of dev_to_node() to cpumask_of_node()
> > without checking if the device's node id is NUMA_NO_NODE, there is
> > global-out-of-bounds detected by KASAN.
> >
> > From the discussion [1], NUMA_NO_NODE really means no node affinity,
> > which also means all cpus should be usable. So the cpumask_of_node()
> > should always return all cpus online when user passes the node id as
> > NUMA_NO_NODE, just like similar semantic that page allocator handles
> > NUMA_NO_NODE.
> >
> > But we cannot really copy the page allocator logic. Simply because the
> > page allocator doesn't enforce the near node affinity. It just picks it
> > up as a preferred node but then it is free to fallback to any other numa
> > node. This is not the case here and node_to_cpumask_map will only restrict
> > to the particular node's cpus which would have really non deterministic
> > behavior depending on where the code is executed. So in fact we really
> > want to return cpu_online_mask for NUMA_NO_NODE.
> >
> > Also there is a debugging version of node_to_cpumask_map() for x86 and
> > arm64, which is only used when CONFIG_DEBUG_PER_CPU_MAPS is defined, this
> > patch changes it to handle NUMA_NO_NODE as normal node_to_cpumask_map().
> >
> > [1] https://lore.kernel.org/patchwork/patch/1125789/
>
> That is bloody unusable, don't do that. Use:
>
> https://lkml.kernel.org/r/$MSGID
>
> if anything. Then I can find it in my local mbox without having to
> resort to touching a mouse and shitty browser software.
>
> (also patchwork is absolute crap for reading email threads)
>
> Anyway, I found it -- I think, I refused to click the link. I replied
> there.
>
> > Signed-off-by: Yunsheng Lin <linyunsheng@huawei.com>
> > Suggested-by: Michal Hocko <mhocko@kernel.org>
> > Acked-by: Michal Hocko <mhocko@suse.com>
>
>
>
> > diff --git a/arch/x86/mm/numa.c b/arch/x86/mm/numa.c
> > index 4123100e..9859acb 100644
> > --- a/arch/x86/mm/numa.c
> > +++ b/arch/x86/mm/numa.c
> > @@ -861,6 +861,9 @@ void numa_remove_cpu(int cpu)
> > */
> > const struct cpumask *cpumask_of_node(int node)
> > {
> > + if (node == NUMA_NO_NODE)
> > + return cpu_online_mask;
>
> This mandates the caller holds cpus_read_lock() or something, I'm pretty
> sure that if I put:
>
> lockdep_assert_cpus_held();
Is this documented somewhere? Also how does that differ from a normal
case when a proper node is used? The cpumask will always be dynamic in
the cpu hotplug presence, right?
> here, it comes apart real quick. Without holding the cpu hotplug lock,
> the online mask is gibberish.
Can the returned cpu mask go away?
--
Michal Hocko
SUSE Labs
next prev parent reply other threads:[~2019-09-23 15:29 UTC|newest]
Thread overview: 53+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-09-17 12:48 [PATCH v6] numa: make node_to_cpumask_map() NUMA_NO_NODE aware Yunsheng Lin
2019-09-23 15:15 ` Peter Zijlstra
2019-09-23 15:28 ` Michal Hocko [this message]
2019-09-23 15:48 ` Peter Zijlstra
2019-09-23 16:52 ` Michal Hocko
2019-09-23 20:34 ` Peter Zijlstra
2019-09-24 1:29 ` Yunsheng Lin
2019-09-24 9:25 ` Peter Zijlstra
2019-09-24 11:07 ` Yunsheng Lin
2019-09-24 11:28 ` Peter Zijlstra
2019-09-24 11:44 ` Yunsheng Lin
2019-09-24 11:58 ` Peter Zijlstra
2019-09-24 12:09 ` Yunsheng Lin
2019-09-24 7:47 ` Michal Hocko
2019-09-24 9:17 ` Peter Zijlstra
2019-09-24 10:56 ` Michal Hocko
2019-09-24 11:23 ` Peter Zijlstra
2019-09-24 11:54 ` Michal Hocko
2019-09-24 12:09 ` Peter Zijlstra
2019-09-24 12:25 ` Michal Hocko
2019-09-24 12:43 ` Peter Zijlstra
2019-09-24 12:59 ` Peter Zijlstra
2019-09-24 13:19 ` Michal Hocko
2019-09-25 9:14 ` Yunsheng Lin
2019-09-25 10:41 ` Peter Zijlstra
2019-10-08 8:38 ` Yunsheng Lin
2019-10-09 12:25 ` Robin Murphy
2019-10-10 6:07 ` Yunsheng Lin
2019-10-10 7:32 ` Michal Hocko
2019-10-11 3:27 ` Yunsheng Lin
2019-10-11 11:15 ` Peter Zijlstra
2019-10-12 6:17 ` Yunsheng Lin
2019-10-12 7:40 ` Greg KH
2019-10-12 9:47 ` Yunsheng Lin
2019-10-12 10:40 ` Greg KH
2019-10-12 10:47 ` Greg KH
2019-10-14 8:00 ` Yunsheng Lin
2019-10-14 9:25 ` Greg KH
2019-10-14 9:49 ` Peter Zijlstra
2019-10-14 10:04 ` Greg KH
2019-10-15 10:40 ` Yunsheng Lin
2019-10-15 16:58 ` Greg KH
2019-10-16 12:07 ` Yunsheng Lin
2019-10-28 9:20 ` Yunsheng Lin
2019-10-29 8:53 ` Michal Hocko
2019-10-30 1:58 ` Yunsheng Lin
2019-10-10 8:56 ` Peter Zijlstra
2019-09-25 10:40 ` Peter Zijlstra
2019-09-25 13:25 ` Michal Hocko
2019-09-25 16:31 ` Peter Zijlstra
2019-09-25 21:45 ` Peter Zijlstra
2019-09-26 9:05 ` Peter Zijlstra
2019-09-26 12:10 ` Peter Zijlstra
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