[3.11.y.z extended stable] Patch "cpufreq: powernow-k8: Initialize per-cpu data-structures properly" has been added to staging queue

[Luis Henriques]

This is a note to let you know that I have just added a patch titled

    cpufreq: powernow-k8: Initialize per-cpu data-structures properly

to the linux-3.11.y-queue branch of the 3.11.y.z extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.11.y-queue

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.11.y.z tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Luis

------

>From 36325cd0c31d448a610cfbc849fd653e5e007914 Mon Sep 17 00:00:00 2001
From: "Srivatsa S. Bhat" <srivatsa.bhat at linux.vnet.ibm.com>
Date: Mon, 17 Feb 2014 16:18:21 +0530
Subject: cpufreq: powernow-k8: Initialize per-cpu data-structures properly

commit c3274763bfc3bf1ececa269ed6e6c4d7ec1c3e5e upstream.

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.

Fix this by initializing the per-cpu data-structures of all the CPUs
in the policy appropriately.

References: https://bugzilla.kernel.org/show_bug.cgi?id=70311
Reported-by: Pierre Ossman <pierre at ossman.eu>
Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat at linux.vnet.ibm.com>
Acked-by: Viresh Kumar <viresh.kumar at linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki at intel.com>
Signed-off-by: Luis Henriques <luis.henriques at canonical.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 c39d189..9292f1f 100644
--- a/drivers/cpufreq/powernow-k8.c
+++ b/drivers/cpufreq/powernow-k8.c
@@ -1100,7 +1100,7 @@ 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)
@@ -1169,7 +1169,9 @@ 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;

@@ -1184,6 +1186,7 @@ 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;
@@ -1194,7 +1197,8 @@ 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;
 }
--
1.9.0