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Re: [PATCH] xen/sched: fix rare error case in cpu_schedule_down()
- To: Jan Beulich <jbeulich@xxxxxxxx>
- From: Juergen Gross <jgross@xxxxxxxx>
- Date: Tue, 25 Jun 2024 12:16:58 +0200
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- Cc: George Dunlap <george.dunlap@xxxxxxxxxx>, Dario Faggioli <dfaggioli@xxxxxxxx>, xen-devel@xxxxxxxxxxxxxxxxxxxx
- Delivery-date: Tue, 25 Jun 2024 10:17:05 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
On 25.06.24 10:33, Jan Beulich wrote:
On 25.06.2024 10:27, Juergen Gross wrote:
In case cpu_schedule_up() is failing to allocate memory for struct
sched_resource,
Or (just to mention it again) in case the function isn't called at all
because some earlier CPU_UP_PREPARE handler fails.
This remark made me looking into the notifier implementation.
I think this patch should be reworked significantly:
In cpu_up() the CPU_UP_CANCELED notifier call is using the same
notifier_block as the one used by CPU_UP_PREPARE before. This means,
that only the handlers which didn't fail for CPU_UP_PREPARE will be
called with CPU_UP_CANCELED.
So there is no such case as "in case the function isn't called at all
because some earlier CPU_UP_PREPARE handler fails".
And a failure of cpu_schedule_up() needs to undo all externally visible
modifications instead of hoping that the CPU_UP_CANCELED notifier will
do that.
So: V2 of the patch will be needed.
Juergen
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