From: Gautham R Shenoy <ego@linux.vnet.ibm.com>
To: Denis Kirjanov <kda@linux-powerpc.org>
Cc: linuxppc-dev@lists.ozlabs.org, ego@linux.vnet.ibm.com
Subject: Re: [PATCH v2] ppc: cpufreq: disable preemption while checking CPU throttling state
Date: Mon, 7 Nov 2016 08:01:47 +0530 [thread overview]
Message-ID: <20161107023147.GA14131@in.ibm.com> (raw)
In-Reply-To: <1478257718-14923-1-git-send-email-kda@linux-powerpc.org>
Hi Denis,
On Fri, Nov 04, 2016 at 07:08:38AM -0400, Denis Kirjanov wrote:
You can provide the config option with which this bug was found in the
change log. I suppose you had enabled CONFIG_DEBUG_PREEMPT.
> [ 67.700897] BUG: using smp_processor_id() in preemptible [00000000] code: cat/7343
> [ 67.700988] caller is .powernv_cpufreq_throttle_check+0x2c/0x710
> [ 67.700998] CPU: 13 PID: 7343 Comm: cat Not tainted 4.8.0-rc5-dirty #1
> [ 67.701038] Call Trace:
> [ 67.701066] [c0000007d25b75b0] [c000000000971378] .dump_stack+0xe4/0x150 (unreliable)
> [ 67.701153] [c0000007d25b7640] [c0000000005162e4] .check_preemption_disabled+0x134/0x150
> [ 67.701238] [c0000007d25b76e0] [c0000000007b63ac] .powernv_cpufreq_throttle_check+0x2c/0x710
> [ 67.701322] [c0000007d25b7790] [c0000000007b6d18] .powernv_cpufreq_target_index+0x288/0x360
> [ 67.701407] [c0000007d25b7870] [c0000000007acee4] .__cpufreq_driver_target+0x394/0x8c0
> [ 67.701491] [c0000007d25b7920] [c0000000007b22ac] .cpufreq_set+0x7c/0xd0
> [ 67.701565] [c0000007d25b79b0] [c0000000007adf50] .store_scaling_setspeed+0x80/0xc0
> [ 67.701650] [c0000007d25b7a40] [c0000000007ae270] .store+0xa0/0x100
> [ 67.701723] [c0000007d25b7ae0] [c0000000003566e8] .sysfs_kf_write+0x88/0xb0
> [ 67.701796] [c0000007d25b7b70] [c0000000003553b8] .kernfs_fop_write+0x178/0x260
> [ 67.701881] [c0000007d25b7c10] [c0000000002ac3cc] .__vfs_write+0x3c/0x1c0
> [ 67.701954] [c0000007d25b7cf0] [c0000000002ad584] .vfs_write+0xc4/0x230
> [ 67.702027] [c0000007d25b7d90] [c0000000002aeef8] .SyS_write+0x58/0x100
> [ 67.702101] [c0000007d25b7e30] [c00000000000bfec] system_call+0x38/0xfc
>
> Signed-off-by: Denis Kirjanov <kda@linux-powerpc.org>
>
> v2: wrap powernv_cpufreq_throttle_check()
> as suggested by Gautham R Shenoy
Looks good otherwise.
Reviewed-by: Gautham R. Shenoy <ego@linux.vnet.ibm.com>
> ---
> drivers/cpufreq/powernv-cpufreq.c | 9 ++++++++-
> 1 file changed, 8 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/cpufreq/powernv-cpufreq.c b/drivers/cpufreq/powernv-cpufreq.c
> index d3ffde8..112e0e2 100644
> --- a/drivers/cpufreq/powernv-cpufreq.c
> +++ b/drivers/cpufreq/powernv-cpufreq.c
> @@ -647,8 +647,15 @@ static int powernv_cpufreq_target_index(struct cpufreq_policy *policy,
> if (unlikely(rebooting) && new_index != get_nominal_index())
> return 0;
>
> - if (!throttled)
> + if (!throttled) {
> + /*
> + * we don't want to be preempted while
> + * checking if the CPU frequency has been throttled
> + */
> + preempt_disable();
> powernv_cpufreq_throttle_check(NULL);
> + preempt_enable();
> + }
>
> cur_msec = jiffies_to_msecs(get_jiffies_64());
>
> --
> 1.8.3.1
>
next prev parent reply other threads:[~2016-11-07 2:31 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-11-04 11:08 [PATCH v2] ppc: cpufreq: disable preemption while checking CPU throttling state Denis Kirjanov
2016-11-07 2:31 ` Gautham R Shenoy [this message]
2016-11-07 5:15 ` Denis Kirjanov
2016-11-07 7:36 ` Michael Ellerman
2016-11-07 8:02 ` Denis Kirjanov
2016-11-08 0:21 ` Michael Ellerman
2016-11-08 3:17 ` Gautham R Shenoy
2016-11-08 8:27 ` Michael Ellerman
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=20161107023147.GA14131@in.ibm.com \
--to=ego@linux.vnet.ibm.com \
--cc=kda@linux-powerpc.org \
--cc=linuxppc-dev@lists.ozlabs.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).