From: Pavel Machek <pavel@ucw.cz>
To: Sasha Levin <sashal@kernel.org>
Cc: linux-kernel@vger.kernel.org, stable@vger.kernel.org,
Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>,
Chen Yu <yu.c.chen@intel.com>,
"Rafael J . Wysocki" <rafael.j.wysocki@intel.com>,
rafael@kernel.org, daniel.lezcano@linaro.org,
linux-pm@vger.kernel.org
Subject: Re: [PATCH AUTOSEL 4.9 4/4] thermal: intel_powerclamp: Use get_cpu() instead of smp_processor_id() to avoid crash
Date: Tue, 11 Oct 2022 13:36:46 +0200 [thread overview]
Message-ID: <20221011113646.GA12080@duo.ucw.cz> (raw)
In-Reply-To: <20221009205508.1204042-4-sashal@kernel.org>
[-- Attachment #1: Type: text/plain, Size: 1626 bytes --]
Hi!
> From: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>
>
> [ Upstream commit 68b99e94a4a2db6ba9b31fe0485e057b9354a640 ]
>
> When CPU 0 is offline and intel_powerclamp is used to inject
> idle, it generates kernel BUG:
>
> BUG: using smp_processor_id() in preemptible [00000000] code: bash/15687
> caller is debug_smp_processor_id+0x17/0x20
> CPU: 4 PID: 15687 Comm: bash Not tainted 5.19.0-rc7+ #57
> Call Trace:
> <TASK>
> dump_stack_lvl+0x49/0x63
> dump_stack+0x10/0x16
> check_preemption_disabled+0xdd/0xe0
> debug_smp_processor_id+0x17/0x20
> powerclamp_set_cur_state+0x7f/0xf9 [intel_powerclamp]
> ...
> ...
>
> Here CPU 0 is the control CPU by default and changed to the current CPU,
> if CPU 0 offlined. This check has to be performed under cpus_read_lock(),
> hence the above warning.
>
> Use get_cpu() instead of smp_processor_id() to avoid this BUG.
This has exactly the same problem as smp_processor_id(), you just
worked around the warning. If it is okay that control_cpu contains
stale value, could we have a comment explaining why?
Thanks,
Pavel
> +++ b/drivers/thermal/intel_powerclamp.c
> @@ -519,8 +519,10 @@ static int start_power_clamp(void)
>
> /* prefer BSP */
> control_cpu = 0;
> - if (!cpu_online(control_cpu))
> - control_cpu = smp_processor_id();
> + if (!cpu_online(control_cpu)) {
> + control_cpu = get_cpu();
> + put_cpu();
> + }
>
> clamping = true;
> schedule_delayed_work(&poll_pkg_cstate_work, 0);
> --
> 2.35.1
--
People of Russia, stop Putin before his war on Ukraine escalates.
[-- Attachment #2: signature.asc --]
[-- Type: application/pgp-signature, Size: 195 bytes --]
next prev parent reply other threads:[~2022-10-11 11:36 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-10-09 20:55 [PATCH AUTOSEL 4.9 1/4] ACPI: video: Add Toshiba Satellite/Portege Z830 quirk Sasha Levin
2022-10-09 20:55 ` [PATCH AUTOSEL 4.9 2/4] MIPS: BCM47XX: Cast memcmp() of function to (void *) Sasha Levin
2022-10-09 20:55 ` [PATCH AUTOSEL 4.9 3/4] powercap: intel_rapl: fix UBSAN shift-out-of-bounds issue Sasha Levin
2022-10-09 20:55 ` [PATCH AUTOSEL 4.9 4/4] thermal: intel_powerclamp: Use get_cpu() instead of smp_processor_id() to avoid crash Sasha Levin
2022-10-11 11:36 ` Pavel Machek [this message]
2022-10-11 13:22 ` Chen Yu
2022-10-12 5:33 ` srinivas pandruvada
2022-10-12 16:58 ` Rafael J. Wysocki
2022-10-13 3:06 ` srinivas pandruvada
2022-10-13 12:05 ` Rafael J. Wysocki
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=20221011113646.GA12080@duo.ucw.cz \
--to=pavel@ucw.cz \
--cc=daniel.lezcano@linaro.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-pm@vger.kernel.org \
--cc=rafael.j.wysocki@intel.com \
--cc=rafael@kernel.org \
--cc=sashal@kernel.org \
--cc=srinivas.pandruvada@linux.intel.com \
--cc=stable@vger.kernel.org \
--cc=yu.c.chen@intel.com \
/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