From: Frederic Weisbecker <frederic@kernel.org>
To: hpa@zytor.com, tglx@linutronix.de, mingo@kernel.org,
linux-kernel@vger.kernel.org, rafael.j.wysocki@intel.com,
npiggin@gmail.com, fweisbec@gmail.com, peterz@infradead.org,
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, 4 May 2019 02:27:34 +0200 [thread overview]
Message-ID: <20190504002733.GB19076@lenoir> (raw)
In-Reply-To: <tip-9219565aa89033a9cfdae788c1940473a1253d6c@git.kernel.org>
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).
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?
Thanks.
next prev parent reply other threads:[~2019-05-04 0:27 UTC|newest]
Thread overview: 38+ 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 ` 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
2019-04-11 3:34 ` 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
2019-04-11 3:34 ` 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
2019-04-11 3:34 ` Nicholas Piggin
2019-04-25 12:02 ` Peter Zijlstra
2019-04-25 12:02 ` Peter Zijlstra
2019-04-26 4:32 ` Nicholas Piggin
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
2019-04-11 3:34 ` 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 [this message]
2019-05-04 6:59 ` Nicholas Piggin
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
2019-04-11 3:34 ` 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
2019-04-25 12:04 ` Peter Zijlstra
2019-04-30 2:46 ` Nicholas Piggin
2019-04-30 2:46 ` Nicholas Piggin
2019-04-30 12:07 ` Peter Zijlstra
2019-04-30 12:07 ` Peter Zijlstra
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