From: "levi.yun" <yeoreum.yun@arm.com>
To: Will Deacon <will@kernel.org>
Cc: catalin.marinas@arm.com, mark.rutland@arm.com,
peterz@infradead.org, mathieu.desnoyers@efficios.com,
linux-arm-kernel@lists.infradead.org,
linux-kernel@vger.kernel.org, nd@arm.com, stable@vger.kernel.org,
Aaron Lu <aaron.lu@intel.com>
Subject: Re: [PATCH] arm64/mm: Add memory barrier for mm_cid
Date: Tue, 5 Mar 2024 18:52:54 +0000 [thread overview]
Message-ID: <4a6bf7f4-afa2-4c7f-b923-d67d48f41954@arm.com> (raw)
In-Reply-To: <20240305171324.GA22616@willie-the-truck>
Hi will.
> We already have a stronger barrier than smp_mb() (dsb ish) in __switch_to().
> Is that not sufficient?
IIUC, It's not sufficient with smp_mb() in __switch_to().
Because, it can be broken in sched_mm_cid_remote_clear()
CPU0 in __schedule() CPU1 in
sched_mm_cid_remote_clear()
rq->curr = new_task;
<no barrier>
mm_get_cid remote_clear
- check valid cid and use it. Invalidate CID.
<barrier>
rq->curr (not observed).
unset the cid
(<<BUG).
If change of rq->curr couldn't be observed in sched_mm_cid_remote_clear(),
It could unset actively used cid.
Note that __switch_to()'s smp_mb() is called AFTER switch_mm_cid().
That means before __switch_to(), there's possibility that
sched_mm_cid_remote_clear() couldn't observe new active task,
after it sets lazy_put on active cid used by new active task.
_______________________________________________
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:[~2024-03-05 18:53 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-03-05 14:53 [PATCH] arm64/mm: Add memory barrier for mm_cid levi.yun
2024-03-05 17:13 ` Will Deacon
2024-03-05 18:52 ` levi.yun [this message]
2024-03-05 20:01 ` Mathieu Desnoyers
2024-03-05 21:07 ` levi.yun
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=4a6bf7f4-afa2-4c7f-b923-d67d48f41954@arm.com \
--to=yeoreum.yun@arm.com \
--cc=aaron.lu@intel.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=mathieu.desnoyers@efficios.com \
--cc=nd@arm.com \
--cc=peterz@infradead.org \
--cc=stable@vger.kernel.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