From: "Jürgen Groß" <jgross@suse.com>
To: Julien Grall <julien@xen.org>, xen-devel@lists.xenproject.org
Cc: "Stefano Stabellini" <sstabellini@kernel.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>,
"Jan Beulich" <jbeulich@suse.com>,
"Roger Pau Monné" <roger.pau@citrix.com>
Subject: Re: [Xen-devel] [PATCH] xen: make sure stop_machine_run() is always called in a tasklet
Date: Thu, 13 Feb 2020 11:01:15 +0100 [thread overview]
Message-ID: <fd9c5b57-001c-cecb-d42f-ab02ef6e8f36@suse.com> (raw)
In-Reply-To: <d11ca0a6-652a-13d8-864a-82893f0969cc@xen.org>
On 13.02.20 10:01, Julien Grall wrote:
> Hi,
>
> On 11/02/2020 10:35, Juergen Gross wrote:
>> With core scheduling active it is mandatory for stop_machine_run() to
>> be called in a tasklet only, as otherwise a scheduling deadlock would
>> occur: stop_machine_run() does a cpu rendezvous by activating a tasklet
>> on all other cpus. In case stop_machine_run() was not called in an idle
>> vcpu it would block scheduling the idle vcpu on its siblings with core
>> scheduling being active, resulting in a hang.
>
> This suggests it is not safe to call stop_machine_run() outside a
> tasklet but still under "idle vCPU" context. However, alternative
> patching on Arm during boot will not be in a tasklet. Is it going to be
> safe?
Yes.
I can rephrase that part to make it clear.
Juergen
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next prev parent reply other threads:[~2020-02-13 10:01 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-02-11 9:35 [Xen-devel] [PATCH] xen: make sure stop_machine_run() is always called in a tasklet Juergen Gross
2020-02-13 9:01 ` Julien Grall
2020-02-13 10:01 ` Jürgen Groß [this message]
2020-02-13 10:09 ` Julien Grall
2020-02-14 14:06 ` Igor Druzhinin
2020-02-14 16:39 ` Jürgen Groß
2020-02-14 17:34 ` Igor Druzhinin
2020-02-15 7:06 ` Jürgen Groß
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