From: Nicholas Piggin <npiggin@gmail.com>
To: Frederic Weisbecker <frederic@kernel.org>,
fweisbec@gmail.com, hpa@zytor.com, linux-kernel@vger.kernel.org,
mingo@kernel.org, peterz@infradead.org,
rafael.j.wysocki@intel.com, tglx@linutronix.de,
torvalds@linux-foundation.org
Cc: linux-tip-commits@vger.kernel.org
Subject: Re: [tip:sched/core] sched/isolation: Require a present CPU in housekeeping mask
Date: Sat, 04 May 2019 16:59:12 +1000 [thread overview]
Message-ID: <1556952021.2xpa7joi2y.astroid@bobo.none> (raw)
In-Reply-To: <20190504002733.GB19076@lenoir>
Frederic Weisbecker's on May 4, 2019 10:27 am:
> On Fri, May 03, 2019 at 10:47:37AM -0700, tip-bot for Nicholas Piggin wrote:
>> Commit-ID: 9219565aa89033a9cfdae788c1940473a1253d6c
>> Gitweb: https://git.kernel.org/tip/9219565aa89033a9cfdae788c1940473a1253d6c
>> Author: Nicholas Piggin <npiggin@gmail.com>
>> AuthorDate: Thu, 11 Apr 2019 13:34:47 +1000
>> Committer: Ingo Molnar <mingo@kernel.org>
>> CommitDate: Fri, 3 May 2019 19:42:58 +0200
>>
>> sched/isolation: Require a present CPU in housekeeping mask
>>
>> During housekeeping mask setup, currently a possible CPU is required.
>> That does not guarantee the CPU would be available at boot time, so
>> check to ensure that at least one present CPU is in the mask.
>
> I have a doubt about the requirements and semantics of cpu_present_mask.
> IIUC a present CPU means that it is physically plugged in (from ACPI
> perspective) but might not be logically plugged in (set on cpu_online_mask).
Right, a superset of cpu_possible_mask, subset of cpu_online_mask. It
means that CPU can be brought online at any time.
> But do we have the guarantee that a present CPU _will_ be online at least once
> right after the boot? After all, kernel parameters such as "maxcpus=" can prevent
> from turning some CPUs on. I guess there are even more creative ways to achieve
> that.
>
> In any case we really require the housekeeper to be forced online. Perhaps
> I missed that enforcement somewhere in the patchset?
No I think you're right, that may be able to boot without anything in
the housekeeping mask. Maybe we can just cpu_up() a CPU in the
housekeeping mask with a warning that it has overidden their SMP
command line option. I'll take a look at it.
Thanks,
Nick
next prev parent reply other threads:[~2019-05-04 6:59 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-04-11 3:34 [PATCH v2 0/5] Allow CPU0 to be nohz full Nicholas Piggin
2019-04-11 3:34 ` [PATCH v2 1/5] sched/core: allow the remote scheduler tick to be started on CPU0 Nicholas Piggin
2019-05-03 11:28 ` [tip:sched/core] sched/core: Allow " tip-bot for Nicholas Piggin
2019-04-11 3:34 ` [PATCH v2 2/5] PM / suspend: add function to disable secondaries for suspend Nicholas Piggin
2019-05-03 11:29 ` [tip:sched/core] power/suspend: Add " tip-bot for Nicholas Piggin
2019-05-03 17:46 ` tip-bot for Nicholas Piggin
2019-04-11 3:34 ` [PATCH v2 3/5] kernel/cpu: Allow non-zero CPU to be primary for suspend / kexec freeze Nicholas Piggin
2019-04-25 12:02 ` Peter Zijlstra
2019-04-26 4:32 ` Nicholas Piggin
2019-05-03 11:29 ` [tip:sched/core] " tip-bot for Nicholas Piggin
2019-05-03 17:46 ` tip-bot for Nicholas Piggin
2019-04-11 3:34 ` [PATCH v2 4/5] kernel/sched/isolation: require a present CPU in housekeeping mask Nicholas Piggin
2019-05-03 11:30 ` [tip:sched/core] sched/isolation: Require " tip-bot for Nicholas Piggin
2019-05-03 17:47 ` tip-bot for Nicholas Piggin
2019-05-03 23:52 ` Frederic Weisbecker
2019-05-04 0:27 ` Frederic Weisbecker
2019-05-04 6:59 ` Nicholas Piggin [this message]
2019-05-06 15:16 ` Frederic Weisbecker
2019-05-06 23:50 ` Nicholas Piggin
2019-05-08 0:35 ` Frederic Weisbecker
2019-05-08 1:38 ` Nicholas Piggin
2019-04-11 3:34 ` [PATCH v2 5/5] nohz_full: Allow the boot CPU to be nohz_full Nicholas Piggin
2019-05-03 11:31 ` [tip:sched/core] " tip-bot for Nicholas Piggin
2019-05-03 17:48 ` tip-bot for Nicholas Piggin
2019-04-25 12:04 ` [PATCH v2 0/5] Allow CPU0 to be nohz full Peter Zijlstra
2019-04-30 2:46 ` Nicholas Piggin
2019-04-30 12:07 ` Peter Zijlstra
Reply instructions:
You may reply publicly 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=1556952021.2xpa7joi2y.astroid@bobo.none \
--to=npiggin@gmail.com \
--cc=frederic@kernel.org \
--cc=fweisbec@gmail.com \
--cc=hpa@zytor.com \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-tip-commits@vger.kernel.org \
--cc=mingo@kernel.org \
--cc=peterz@infradead.org \
--cc=rafael.j.wysocki@intel.com \
--cc=tglx@linutronix.de \
--cc=torvalds@linux-foundation.org \
/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
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox
all inboxes | Powered by JetHome®