From: Dietmar Eggemann <dietmar.eggemann@arm.com>
To: Phil Auld <pauld@redhat.com>, linux-kernel@vger.kernel.org
Cc: Catalin Marinas <catalin.marinas@arm.com>,
Will Deacon <will@kernel.org>,
Mark Rutland <mark.rutland@arm.com>,
Peter Zijlstra <peterz@infradead.org>,
linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH v2] arch/arm64: Fix topology initialization for core scheduling
Date: Thu, 31 Mar 2022 11:04:31 +0200 [thread overview]
Message-ID: <66f29bee-e26c-b40e-c3af-79d5297565d8@arm.com> (raw)
In-Reply-To: <20220330155611.30216-1-pauld@redhat.com>
On 30/03/2022 17:56, Phil Auld wrote:
> Arm64 systems rely on store_cpu_topology() to call update_siblings_masks()
> to transfer the toplogy to the various cpu masks. This needs to be done
> before the call to notify_cpu_starting() which tells the scheduler about
> each cpu found, otherwise the core scheduling data structures are setup
> in a way that does not match the actual topology.
>
> Without this change stress-ng (which enables core scheduling in its prctl
> tests) causes a warning and then a crash (trimmed for legibility):
>
> [ 1853.805168] ------------[ cut here ]------------
> [ 1853.809784] task_rq(b)->core != rq->core
> [ 1853.809792] WARNING: CPU: 117 PID: 0 at kernel/sched/fair.c:11102 cfs_prio_less+0x1b4/0x1c4
> ...
> [ 1854.015210] Unable to handle kernel NULL pointer dereference at virtual address 0000000000000010
> ...
> [ 1854.231256] Call trace:
> [ 1854.233689] pick_next_task+0x3dc/0x81c
> [ 1854.237512] __schedule+0x10c/0x4cc
> [ 1854.240988] schedule_idle+0x34/0x54
>
> Fixes: 9edeaea1bc45 ("sched: Core-wide rq->lock")
> Signed-off-by: Phil Auld <pauld@redhat.com>
> ---
> This is a similar issue to
> f2703def339c ("MIPS: smp: fill in sibling and core maps earlier")
> which fixed it for MIPS.
>
> v2: Fixed the commit message. No code change.
Ah, the reason is that smt_mask is not correctly setup, so we bail on
`cpumask_weight(smt_mask) == 1` for !leaders in:
notify_cpu_starting()
cpuhp_invoke_callback_range()
sched_cpu_starting()
sched_core_cpu_starting()
which leads to rq->core not being correctly set for !leader-rq's.
LGTM. Tested on: HPE Apollo 70 X1
Reviewed-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
Tested-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
[...]
_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
next prev parent reply other threads:[~2022-03-31 9:05 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-03-30 15:56 [PATCH v2] arch/arm64: Fix topology initialization for core scheduling Phil Auld
2022-03-31 9:04 ` Dietmar Eggemann [this message]
2022-03-31 13:21 ` Phil Auld
2022-03-31 14:37 ` Dietmar Eggemann
2022-03-31 14:53 ` Phil Auld
2022-03-31 15:49 ` Dietmar Eggemann
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=66f29bee-e26c-b40e-c3af-79d5297565d8@arm.com \
--to=dietmar.eggemann@arm.com \
--cc=catalin.marinas@arm.com \
--cc=linux-arm-kernel@lists.infradead.org \
--cc=linux-kernel@vger.kernel.org \
--cc=mark.rutland@arm.com \
--cc=pauld@redhat.com \
--cc=peterz@infradead.org \
--cc=will@kernel.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;
as well as URLs for NNTP newsgroup(s).