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

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Date:	Mon, 17 Feb 2014 16:18:21 +0530
From:	"Srivatsa S. Bhat" <srivatsa.bhat@...ux.vnet.ibm.com>
To:	pierre-list@...man.eu, rjw@...ysocki.net
Cc:	viresh.kumar@...aro.org, linux-pm@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	"Srivatsa S. Bhat" <srivatsa.bhat@...ux.vnet.ibm.com>
Subject: [PATCH] cpufreq,
 powernow-k8: Initialize per-cpu data-structures properly

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;
 }

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