From: Catalin Marinas <catalin.marinas@arm.com>
To: Mark Rutland <mark.rutland@arm.com>
Cc: linux-arm-kernel@lists.infradead.org, andre.przywara@arm.com,
ardb@kernel.org, james.morse@arm.com, joey.gouly@arm.com,
suzuki.poulose@arm.com, will@kernel.org
Subject: Re: [PATCH 1/4] arm64: alternative: wait for other CPUs before patching
Date: Fri, 10 Dec 2021 14:49:59 +0000 [thread overview]
Message-ID: <YbNpF6t4DQ4aTqrs@arm.com> (raw)
In-Reply-To: <20211203104723.3412383-2-mark.rutland@arm.com>
On Fri, Dec 03, 2021 at 10:47:20AM +0000, Mark Rutland wrote:
> In __apply_alternatives_multi_stop() we have a "really simple polling
> protocol" to avoid patching code that is concurrently executed on other
> CPUs. Secondary CPUs wait for the boot CPU to signal that patching is
> complete, but the boot CPU doesn't wait for secondaries to enter the
> polling loop, and it's possible that patching starts while secondaries
> are still within the stop_machine logic.
>
> Let's fix this by adding a vaguely simple polling protocol where the
> boot CPU waits for secondaries to signal that they have entered the
> unpatchable stop function. We can use the arch_atomic_*() functions for
> this, as they are not patched with alternatives.
>
> At the same time, let's make `all_alternatives_applied` local to
> __apply_alternatives_multi_stop(), since it is only used there, and this
> makes the code a little clearer.
Doesn't the stop_machine() mechanism wait for the CPUs to get in the
same state before calling our function or we need another stop at a
lower level in the arch code?
--
Catalin
_______________________________________________
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:[~2021-12-10 14:51 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-12-03 10:47 [PATCH 0/4] arm64: ensure CPUs are quiescent before patching Mark Rutland
2021-12-03 10:47 ` [PATCH 1/4] arm64: alternative: wait for other CPUs " Mark Rutland
2021-12-10 14:49 ` Catalin Marinas [this message]
2021-12-13 13:01 ` Mark Rutland
2021-12-13 13:27 ` Will Deacon
2021-12-13 13:31 ` Will Deacon
2021-12-13 13:41 ` Will Deacon
2021-12-13 13:54 ` Mark Rutland
2021-12-14 16:01 ` Will Deacon
2021-12-13 13:49 ` Mark Rutland
2021-12-03 10:47 ` [PATCH 2/4] arm64: insn: " Mark Rutland
2021-12-03 10:47 ` [PATCH 3/4] arm64: patching: unify stop_machine() patch synchronization Mark Rutland
2021-12-03 10:47 ` [PATCH 4/4] arm64: patching: mask exceptions in patch_machine() Mark Rutland
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=YbNpF6t4DQ4aTqrs@arm.com \
--to=catalin.marinas@arm.com \
--cc=andre.przywara@arm.com \
--cc=ardb@kernel.org \
--cc=james.morse@arm.com \
--cc=joey.gouly@arm.com \
--cc=linux-arm-kernel@lists.infradead.org \
--cc=mark.rutland@arm.com \
--cc=suzuki.poulose@arm.com \
--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).