From: "Roger Pau Monné" <roger.pau@citrix.com>
To: Jan Beulich <jbeulich@suse.com>
Cc: Stefano Stabellini <sstabellini@kernel.org>,
Julien Grall <julien@xen.org>, Wei Liu <wl@xen.org>,
Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>,
George Dunlap <George.Dunlap@eu.citrix.com>,
Andrew Cooper <andrew.cooper3@citrix.com>,
Ian Jackson <ian.jackson@eu.citrix.com>,
xen-devel@lists.xenproject.org
Subject: Re: [Xen-devel] [PATCH 1/2] smp: convert the cpu maps lock into a rw lock
Date: Wed, 19 Feb 2020 14:19:08 +0100 [thread overview]
Message-ID: <20200219131908.GA4679@Air-de-Roger> (raw)
In-Reply-To: <d1ab3bc4-5b9e-25c7-130d-c64e91f7705c@suse.com>
On Wed, Feb 19, 2020 at 01:56:02PM +0100, Jan Beulich wrote:
> On 13.02.2020 12:32, Roger Pau Monne wrote:
> > void __init register_cpu_notifier(struct notifier_block *nb)
> > {
> > - if ( !spin_trylock(&cpu_add_remove_lock) )
> > + if ( !write_trylock(&cpu_add_remove_lock) )
> > BUG(); /* Should never fail as we are called only during boot. */
> > notifier_chain_register(&cpu_chain, nb);
> > - spin_unlock(&cpu_add_remove_lock);
> > + write_unlock(&cpu_add_remove_lock);
> > }
>
> So why a write lock here?
notifier_chain_register calls cannot be made in parallel, as they
modify the underlying notifier list without taking any additional
locks.
Thanks, Roger.
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next prev parent reply other threads:[~2020-02-19 13:19 UTC|newest]
Thread overview: 30+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-02-13 11:32 [Xen-devel] [PATCH 0/2] smp: convert cpu_add_remove_lock int a rw lock Roger Pau Monne
2020-02-13 11:32 ` [Xen-devel] [PATCH 1/2] smp: convert the cpu maps lock into " Roger Pau Monne
2020-02-19 12:08 ` Julien Grall
2020-02-19 12:56 ` Jan Beulich
2020-02-19 13:19 ` Roger Pau Monné [this message]
2020-02-19 13:42 ` Jan Beulich
2020-02-19 14:38 ` Roger Pau Monné
2020-02-20 8:13 ` Jan Beulich
2020-02-20 8:27 ` Jürgen Groß
2020-02-20 8:36 ` Jan Beulich
2020-02-20 8:57 ` Julien Grall
2020-02-20 9:20 ` Roger Pau Monné
2020-02-13 11:32 ` [Xen-devel] [PATCH 2/2] smp: convert cpu_hotplug_begin into a blocking lock acquisition Roger Pau Monne
2020-02-19 12:59 ` Jan Beulich
2020-02-19 13:22 ` Roger Pau Monné
2020-02-19 13:44 ` Jan Beulich
2020-02-19 14:45 ` Roger Pau Monné
2020-02-19 14:57 ` Jan Beulich
2020-02-19 15:07 ` Andrew Cooper
2020-02-19 16:06 ` Jan Beulich
2020-02-19 16:26 ` Roger Pau Monné
2020-02-19 17:06 ` Jan Beulich
2020-02-19 16:54 ` Andrew Cooper
2020-02-19 16:08 ` Roger Pau Monné
2020-02-19 17:03 ` Jan Beulich
2020-02-20 8:16 ` Jan Beulich
2020-02-21 10:23 ` Roger Pau Monné
2020-02-21 13:06 ` Jan Beulich
2020-02-19 14:58 ` Andrew Cooper
2020-02-19 12:22 ` [Xen-devel] [PATCH 0/2] smp: convert cpu_add_remove_lock int a rw lock Andrew Cooper
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