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Message-ID: <20120919175753.GL8474@google.com>
Date: Wed, 19 Sep 2012 10:57:53 -0700
From: Tejun Heo <tj@...nel.org>
To: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: "Rafael J. Wysocki" <rjw@...k.pl>, linux-kernel@...r.kernel.org,
cpufreq@...r.kernel.org, linux-pm@...r.kernel.org,
Duncan <1i5t5.duncan@....net>,
Andreas Herrmann <andreas.herrmann3@....com>,
Jiri Kosina <trivial@...nel.org>
Subject: [GIT PULL] workqueue / powernow-k8 fix for v3.6-rc6
Hello, Linus.
This is the fix for the bug where cpufreq/powernow-k8 was tripping
BUG_ON() in try_to_wake_up_local() by migrating workqueue worker to a
different CPU.
https://bugzilla.kernel.org/show_bug.cgi?id=47301
As discussed, the fix is now two parts - one to reimplement
work_on_cpu() so that it doesn't create a new kthread each time and
the actual fix which makes powernow-k8 use work_on_cpu() instead of
performing manual migration.
While pretty late in the merge cycle, both changes are on the safer
side. Jiri and I verified two existing users of work_on_cpu() and
Duncan confirmed that the powernow-k8 fix survived about 18 hours of
testing.
Please consider pulling from the following branch to receive the fix.
git://git.kernel.org/pub/scm/linux/kernel/git/tj/wq.git for-3.6-fixes
Thanks.
Tejun Heo (2):
workqueue: reimplement work_on_cpu() using system_wq
cpufreq/powernow-k8: workqueue user shouldn't migrate the kworker to another CPU
drivers/cpufreq/powernow-k8.c | 63 ++++++++++++++++++++++-------------------
kernel/workqueue.c | 25 +++++-----------
2 files changed, 42 insertions(+), 46 deletions(-)
diff --git a/drivers/cpufreq/powernow-k8.c b/drivers/cpufreq/powernow-k8.c
index c0e8164..1a40935 100644
--- a/drivers/cpufreq/powernow-k8.c
+++ b/drivers/cpufreq/powernow-k8.c
@@ -35,7 +35,6 @@
#include <linux/slab.h>
#include <linux/string.h>
#include <linux/cpumask.h>
-#include <linux/sched.h> /* for current / set_cpus_allowed() */
#include <linux/io.h>
#include <linux/delay.h>
@@ -1139,16 +1138,23 @@ static int transition_frequency_pstate(struct powernow_k8_data *data,
return res;
}
-/* Driver entry point to switch to the target frequency */
-static int powernowk8_target(struct cpufreq_policy *pol,
- unsigned targfreq, unsigned relation)
+struct powernowk8_target_arg {
+ struct cpufreq_policy *pol;
+ unsigned targfreq;
+ unsigned relation;
+};
+
+static long powernowk8_target_fn(void *arg)
{
- cpumask_var_t oldmask;
+ struct powernowk8_target_arg *pta = arg;
+ struct cpufreq_policy *pol = pta->pol;
+ unsigned targfreq = pta->targfreq;
+ unsigned relation = pta->relation;
struct powernow_k8_data *data = per_cpu(powernow_data, pol->cpu);
u32 checkfid;
u32 checkvid;
unsigned int newstate;
- int ret = -EIO;
+ int ret;
if (!data)
return -EINVAL;
@@ -1156,29 +1162,16 @@ static int powernowk8_target(struct cpufreq_policy *pol,
checkfid = data->currfid;
checkvid = data->currvid;
- /* only run on specific CPU from here on. */
- /* This is poor form: use a workqueue or smp_call_function_single */
- if (!alloc_cpumask_var(&oldmask, GFP_KERNEL))
- return -ENOMEM;
-
- cpumask_copy(oldmask, tsk_cpus_allowed(current));
- set_cpus_allowed_ptr(current, cpumask_of(pol->cpu));
-
- if (smp_processor_id() != pol->cpu) {
- printk(KERN_ERR PFX "limiting to cpu %u failed\n", pol->cpu);
- goto err_out;
- }
-
if (pending_bit_stuck()) {
printk(KERN_ERR PFX "failing targ, change pending bit set\n");
- goto err_out;
+ return -EIO;
}
pr_debug("targ: cpu %d, %d kHz, min %d, max %d, relation %d\n",
pol->cpu, targfreq, pol->min, pol->max, relation);
if (query_current_values_with_pending_wait(data))
- goto err_out;
+ return -EIO;
if (cpu_family != CPU_HW_PSTATE) {
pr_debug("targ: curr fid 0x%x, vid 0x%x\n",
@@ -1196,7 +1189,7 @@ static int powernowk8_target(struct cpufreq_policy *pol,
if (cpufreq_frequency_table_target(pol, data->powernow_table,
targfreq, relation, &newstate))
- goto err_out;
+ return -EIO;
mutex_lock(&fidvid_mutex);
@@ -1209,9 +1202,8 @@ static int powernowk8_target(struct cpufreq_policy *pol,
ret = transition_frequency_fidvid(data, newstate);
if (ret) {
printk(KERN_ERR PFX "transition frequency failed\n");
- ret = 1;
mutex_unlock(&fidvid_mutex);
- goto err_out;
+ return 1;
}
mutex_unlock(&fidvid_mutex);
@@ -1220,12 +1212,25 @@ static int powernowk8_target(struct cpufreq_policy *pol,
data->powernow_table[newstate].index);
else
pol->cur = find_khz_freq_from_fid(data->currfid);
- ret = 0;
-err_out:
- set_cpus_allowed_ptr(current, oldmask);
- free_cpumask_var(oldmask);
- return ret;
+ return 0;
+}
+
+/* Driver entry point to switch to the target frequency */
+static int powernowk8_target(struct cpufreq_policy *pol,
+ unsigned targfreq, unsigned relation)
+{
+ struct powernowk8_target_arg pta = { .pol = pol, .targfreq = targfreq,
+ .relation = relation };
+
+ /*
+ * Must run on @pol->cpu. cpufreq core is responsible for ensuring
+ * that we're bound to the current CPU and pol->cpu stays online.
+ */
+ if (smp_processor_id() == pol->cpu)
+ return powernowk8_target_fn(&pta);
+ else
+ return work_on_cpu(pol->cpu, powernowk8_target_fn, &pta);
}
/* Driver entry point to verify the policy and range of frequencies */
diff --git a/kernel/workqueue.c b/kernel/workqueue.c
index b80065a..3c5a79e 100644
--- a/kernel/workqueue.c
+++ b/kernel/workqueue.c
@@ -3576,18 +3576,17 @@ static int __devinit workqueue_cpu_down_callback(struct notifier_block *nfb,
#ifdef CONFIG_SMP
struct work_for_cpu {
- struct completion completion;
+ struct work_struct work;
long (*fn)(void *);
void *arg;
long ret;
};
-static int do_work_for_cpu(void *_wfc)
+static void work_for_cpu_fn(struct work_struct *work)
{
- struct work_for_cpu *wfc = _wfc;
+ struct work_for_cpu *wfc = container_of(work, struct work_for_cpu, work);
+
wfc->ret = wfc->fn(wfc->arg);
- complete(&wfc->completion);
- return 0;
}
/**
@@ -3602,19 +3601,11 @@ static int do_work_for_cpu(void *_wfc)
*/
long work_on_cpu(unsigned int cpu, long (*fn)(void *), void *arg)
{
- struct task_struct *sub_thread;
- struct work_for_cpu wfc = {
- .completion = COMPLETION_INITIALIZER_ONSTACK(wfc.completion),
- .fn = fn,
- .arg = arg,
- };
+ struct work_for_cpu wfc = { .fn = fn, .arg = arg };
- sub_thread = kthread_create(do_work_for_cpu, &wfc, "work_for_cpu");
- if (IS_ERR(sub_thread))
- return PTR_ERR(sub_thread);
- kthread_bind(sub_thread, cpu);
- wake_up_process(sub_thread);
- wait_for_completion(&wfc.completion);
+ INIT_WORK_ONSTACK(&wfc.work, work_for_cpu_fn);
+ schedule_work_on(cpu, &wfc.work);
+ flush_work(&wfc.work);
return wfc.ret;
}
EXPORT_SYMBOL_GPL(work_on_cpu);
--
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