Linux-MIPS Archive on lore.kernel.org
 help / color / Atom feed
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,
	len.brown@intel.com, axboe@kernel.dk, dledford@redhat.com,
	jeffrey.t.kirsher@intel.com, linux-alpha@vger.kernel.org,
	naveen.n.rao@linux.vnet.ibm.com, mwb@linux.vnet.ibm.com,
	linuxppc-dev@lists.ozlabs.org, linux-s390@vger.kernel.org,
	linux-sh@vger.kernel.org, sparclinux@vger.kernel.org,
	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
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

  reply index

Thread overview: 53+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-09-17 12:48 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

Reply instructions:

You may reply publically to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20190923152856.GB17206@dhcp22.suse.cz \
    --to=mhocko@kernel.org \
    --cc=akpm@linux-foundation.org \
    --cc=anshuman.khandual@arm.com \
    --cc=axboe@kernel.dk \
    --cc=benh@kernel.crashing.org \
    --cc=borntraeger@de.ibm.com \
    --cc=bp@alien8.de \
    --cc=cai@lca.pw \
    --cc=catalin.marinas@arm.com \
    --cc=chenhc@lemote.com \
    --cc=dalias@libc.org \
    --cc=dave.hansen@linux.intel.com \
    --cc=davem@davemloft.net \
    --cc=dledford@redhat.com \
    --cc=gor@linux.ibm.com \
    --cc=gregkh@linuxfoundation.org \
    --cc=heiko.carstens@de.ibm.com \
    --cc=hpa@zytor.com \
    --cc=ink@jurassic.park.msu.ru \
    --cc=jeffrey.t.kirsher@intel.com \
    --cc=jhogan@kernel.org \
    --cc=jiaxun.yang@flygoat.com \
    --cc=len.brown@intel.com \
    --cc=linux-alpha@vger.kernel.org \
    --cc=linux-arm-kernel@lists.infradead.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linux-mips@vger.kernel.org \
    --cc=linux-s390@vger.kernel.org \
    --cc=linux-sh@vger.kernel.org \
    --cc=linuxppc-dev@lists.ozlabs.org \
    --cc=linyunsheng@huawei.com \
    --cc=luto@kernel.org \
    --cc=mattst88@gmail.com \
    --cc=mingo@redhat.com \
    --cc=mpe@ellerman.id.au \
    --cc=mwb@linux.vnet.ibm.com \
    --cc=naveen.n.rao@linux.vnet.ibm.com \
    --cc=paul.burton@mips.com \
    --cc=paulus@samba.org \
    --cc=peterz@infradead.org \
    --cc=rafael@kernel.org \
    --cc=ralf@linux-mips.org \
    --cc=robin.murphy@arm.com \
    --cc=rppt@linux.ibm.com \
    --cc=rth@twiddle.net \
    --cc=sparclinux@vger.kernel.org \
    --cc=tbogendoerfer@suse.de \
    --cc=tglx@linutronix.de \
    --cc=will@kernel.org \
    --cc=x86@kernel.org \
    --cc=ysato@users.sourceforge.jp \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

Linux-MIPS Archive on lore.kernel.org

Archives are clonable:
	git clone --mirror https://lore.kernel.org/linux-mips/0 linux-mips/git/0.git

	# If you have public-inbox 1.1+ installed, you may
	# initialize and index your mirror using the following commands:
	public-inbox-init -V2 linux-mips linux-mips/ https://lore.kernel.org/linux-mips \
		linux-mips@vger.kernel.org
	public-inbox-index linux-mips

Example config snippet for mirrors

Newsgroup available over NNTP:
	nntp://nntp.lore.kernel.org/org.kernel.vger.linux-mips


AGPL code for this site: git clone https://public-inbox.org/public-inbox.git