linux-kernel - Re: [PATCH] cpufreq, powernow-k8: Initialize per-cpu data-structures properly

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Message-ID: <CAKohpo=nYQpZFh5=2g=REDyf-LKaMqJvnZ=pSncawLFpr1K_+Q@mail.gmail.com>
Date:	Mon, 17 Feb 2014 16:35:08 +0530
From:	Viresh Kumar <viresh.kumar@...aro.org>
To:	"Srivatsa S. Bhat" <srivatsa.bhat@...ux.vnet.ibm.com>
Cc:	Pierre Ossman <pierre-list@...man.eu>,
	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	"linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] cpufreq, powernow-k8: Initialize per-cpu data-structures properly

On 17 February 2014 16:18, Srivatsa S. Bhat
<srivatsa.bhat@...ux.vnet.ibm.com> wrote:
> The powernow-k8 driver maintains a per-cpu data-structure called powernow_data
> that is used to perform the frequency transitions. It initializes this data-
> structure only for the policy->cpu. So, accesses to this data-structure by
> other CPUs results in various problems because they would have been
> uninitialized.
>
> Specifically, if a cpu (!= policy->cpu) invokes the drivers' ->get() function,
> it returns 0 as the KHz value, since its per-cpu memory doesn't point to
> anything valid. This causes problems during suspend/resume since
> cpufreq_update_policy() tries to enforce this (0 KHz) as the current frequency
> of the CPU, and this madness gets propagated to adjust_jiffies() as well.
> Eventually, lots of things start breaking down, including the r8169 ethernet
> card, in one particularly interesting case reported by Pierre Ossman.
>
> https://bugzilla.kernel.org/show_bug.cgi?id=70311
>
> Fix this by initializing the per-cpu data-structures of _all_ the CPUs
> in the policy appropriately.
>
> Cc: stable@...r.kernel.org
> Reported-by: Pierre Ossman <pierre@...man.eu>
> Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@...ux.vnet.ibm.com>
> ---
>
>  drivers/cpufreq/powernow-k8.c |   10 +++++++---
>  1 file changed, 7 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/cpufreq/powernow-k8.c b/drivers/cpufreq/powernow-k8.c
> index e10b646..6684e03 100644
> --- a/drivers/cpufreq/powernow-k8.c
> +++ b/drivers/cpufreq/powernow-k8.c
> @@ -1076,7 +1076,7 @@ static int powernowk8_cpu_init(struct cpufreq_policy *pol)
>  {
>         struct powernow_k8_data *data;
>         struct init_on_cpu init_on_cpu;
> -       int rc;
> +       int rc, cpu;
>
>         smp_call_function_single(pol->cpu, check_supported_cpu, &rc, 1);
>         if (rc)
> @@ -1140,7 +1140,9 @@ static int powernowk8_cpu_init(struct cpufreq_policy *pol)
>         pr_debug("cpu_init done, current fid 0x%x, vid 0x%x\n",
>                  data->currfid, data->currvid);
>
> -       per_cpu(powernow_data, pol->cpu) = data;
> +       /* Point all the CPUs in this policy to the same data */
> +       for_each_cpu(cpu, pol->cpus)
> +               per_cpu(powernow_data, cpu) = data;
>
>         return 0;
>
> @@ -1155,6 +1157,7 @@ err_out:
>  static int powernowk8_cpu_exit(struct cpufreq_policy *pol)
>  {
>         struct powernow_k8_data *data = per_cpu(powernow_data, pol->cpu);
> +       int cpu;
>
>         if (!data)
>                 return -EINVAL;
> @@ -1165,7 +1168,8 @@ static int powernowk8_cpu_exit(struct cpufreq_policy *pol)
>
>         kfree(data->powernow_table);
>         kfree(data);
> -       per_cpu(powernow_data, pol->cpu) = NULL;
> +       for_each_cpu(cpu, pol->cpus)
> +               per_cpu(powernow_data, cpu) = NULL;
>
>         return 0;

Acked-by: Viresh Kumar <viresh.kumar@...aro.org>
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