From: Dario Faggioli <dfaggioli@suse.com>
To: Juergen Gross <jgross@suse.com>, xen-devel@lists.xenproject.org
Cc: George Dunlap <george.dunlap@eu.citrix.com>,
Meng Xu <mengxu@cis.upenn.edu>
Subject: Re: [Xen-devel] [PATCH] xen/sched: remove sched_init_pdata()
Date: Tue, 11 Feb 2020 11:37:20 +0100 [thread overview]
Message-ID: <ab00b9b4e25d9d690c803ae5a986881cfa1b6fbd.camel@suse.com> (raw)
In-Reply-To: <20200210153920.4297-1-jgross@suse.com>
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On Mon, 2020-02-10 at 16:39 +0100, Juergen Gross wrote:
> sched_init_pdata() is used nowhere, it can be removed. Same applies
> to
> the .init_pdata hook of the per-scheduler interface.
>
Right, and that appear to be the case since
f855dd962523b6cb47a92037bdd28b1485141abe ("sched: add minimalistic idle
scheduler for free cpus"), which removed all call sites.
And that is because switching to a scheduler always happens via
switch_sched from the idle scheduler, and it's there that we do all the
initializations, right?
This change is obviously doing the right thing, removing code that is
never called! :-)
Can we, though:
- add a mention to the commit above and a quick explanation of things
in the changelog?
- update the following comments too:
1) in cpu_schedule_callback()
"* This happens by calling the deinit_pdata and free_pdata hooks, in this
* order. If no per-pCPU memory was allocated, there is no need to
* provide an implementation of free_pdata. deinit_pdata may, however,
* be necessary/useful in this case too (e.g., it can undo something done
* on scheduler wide data structure during init_pdata). Both deinit_pdata
* and free_pdata are called during CPU_DEAD."
2) schedule_cpu_add()
"* - a valid instance of per-CPU scheduler specific data, as it is
* allocated by sched_alloc_pdata(). Note that we do not want to
* initialize it yet (i.e., we are not calling sched_init_pdata()).
* That will be done by the target scheduler, in sched_switch_sched(),
* in proper ordering and with locking."
Regards
--
Dario Faggioli, Ph.D
http://about.me/dario.faggioli
Virtualization Software Engineer
SUSE Labs, SUSE https://www.suse.com/
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next prev parent reply other threads:[~2020-02-11 10:37 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-02-10 15:39 [Xen-devel] [PATCH] xen/sched: remove sched_init_pdata() Juergen Gross
2020-02-11 10:37 ` Dario Faggioli [this message]
2020-02-11 10:39 ` Jürgen Groß
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