Commit c5c473e2 authored by Linus Torvalds's avatar Linus Torvalds
Browse files

Merge branch 'for-3.6-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/wq 

Pull workqueue / powernow-k8 fix from Tejun Heo:
 "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."

* 'for-3.6-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/wq:
  cpufreq/powernow-k8: workqueue user shouldn't migrate the kworker to another CPU
  workqueue: reimplement work_on_cpu() using system_wq
parents 925a6f0b 6889125b

drivers/cpufreq/powernow-k8.c

+34 −29
Original line number Diff line number Diff line
@@ -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 */

kernel/workqueue.c

+8 −17
Original line number Diff line number Diff line
@@ -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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