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Date: Fri, 3 Jul 2009 12:24:43 -0700
From: "Pallipadi, Venkatesh" <venkatesh.pallipadi@...el.com>
To: Mathieu Desnoyers <mathieu.desnoyers@...ymtl.ca>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
Dave Jones <davej@...hat.com>,
Thomas Renninger <trenn@...e.de>,
"cpufreq@...r.kernel.org" <cpufreq@...r.kernel.org>,
"kernel-testers@...r.kernel.org" <kernel-testers@...r.kernel.org>,
Ingo Molnar <mingo@...e.hu>, "rjw@...k.pl" <rjw@...k.pl>,
Dave Young <hidave.darkstar@...il.com>,
Pekka Enberg <penberg@...helsinki.fi>
CC: "Li, Shaohua" <shaohua.li@...el.com>,
Rusty Russell <rusty@...tcorp.com.au>,
"sven.wegener@...aler.net" <sven.wegener@...aler.net>
Subject: RE: [patch 2.6.30 2/4] CPUFREQ: fix (utter) cpufreq_add_dev mess
>-----Original Message-----
>From: Mathieu Desnoyers [mailto:mathieu.desnoyers@...ymtl.ca]
>Sent: Friday, July 03, 2009 8:25 AM
>To: linux-kernel@...r.kernel.org; Pallipadi, Venkatesh; Dave
>Jones; Thomas Renninger; cpufreq@...r.kernel.org;
>kernel-testers@...r.kernel.org; Ingo Molnar; rjw@...k.pl; Dave
>Young; Pekka Enberg
>Cc: Mathieu Desnoyers; Li, Shaohua; Rusty Russell;
>sven.wegener@...aler.net
>Subject: [patch 2.6.30 2/4] CPUFREQ: fix (utter) cpufreq_add_dev mess
>
>OK, I've tried to clean it up the best I could, but please
>test this with
>concurrent cpu hotplug and cpufreq add/remove in loops. I'm
>sure we will make
>other interesting findings.
>
This is a good and needed cleanup of cpufreq_add_dev.
>This is step one of fixing the overall locking dependency mess
>in cpufreq.
>
>Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@...ymtl.ca>
>CC: Venkatesh Pallipadi <venkatesh.pallipadi@...el.com>
>CC: rjw@...k.pl
>CC: mingo@...e.hu
>CC: Shaohua Li <shaohua.li@...el.com>
>CC: Pekka Enberg <penberg@...helsinki.fi>
>CC: Dave Young <hidave.darkstar@...il.com>
>CC: "Rafael J. Wysocki" <rjw@...k.pl>
>CC: Rusty Russell <rusty@...tcorp.com.au>
>CC: sven.wegener@...aler.net
>CC: cpufreq@...r.kernel.org
>CC: Thomas Renninger <trenn@...e.de>
>---
> drivers/cpufreq/cpufreq.c | 65
>++++++++++++++++++++++++++++------------------
> 1 file changed, 40 insertions(+), 25 deletions(-)
>
>Index: linux-2.6-lttng/drivers/cpufreq/cpufreq.c
>===================================================================
>--- linux-2.6-lttng.orig/drivers/cpufreq/cpufreq.c
>2009-07-02 23:59:08.000000000 -0400
>+++ linux-2.6-lttng/drivers/cpufreq/cpufreq.c 2009-07-02
>23:59:09.000000000 -0400
>@@ -763,6 +763,10 @@ static struct kobj_type ktype_cpufreq =
> * cpufreq_add_dev - add a CPU device
> *
> * Adds the cpufreq interface for a CPU device.
>+ *
>+ * The Oracle says: try running cpufreq
>registration/unregistration concurrently
>+ * with with cpu hotplugging and all hell will break loose.
>Tried to clean this
>+ * mess up, but more thorough testing is needed. - Mathieu
> */
> static int cpufreq_add_dev(struct sys_device *sys_dev)
> {
>@@ -806,15 +810,12 @@ static int cpufreq_add_dev(struct sys_de
> goto nomem_out;
> }
> if (!alloc_cpumask_var(&policy->cpus, GFP_KERNEL)) {
>- kfree(policy);
> ret = -ENOMEM;
>- goto nomem_out;
>+ goto err_free_policy;
> }
> if (!zalloc_cpumask_var(&policy->related_cpus, GFP_KERNEL)) {
>- free_cpumask_var(policy->cpus);
>- kfree(policy);
> ret = -ENOMEM;
>- goto nomem_out;
>+ goto err_free_cpumask;
> }
>
> policy->cpu = cpu;
>@@ -822,7 +823,8 @@ static int cpufreq_add_dev(struct sys_de
>
> /* Initially set CPU itself as the policy_cpu */
> per_cpu(policy_cpu, cpu) = cpu;
>- lock_policy_rwsem_write(cpu);
>+ ret = (lock_policy_rwsem_write(cpu) < 0);
>+ WARN_ON(ret);
>
> init_completion(&policy->kobj_unregister);
> INIT_WORK(&policy->update, handle_update);
>@@ -835,7 +837,7 @@ static int cpufreq_add_dev(struct sys_de
> ret = cpufreq_driver->init(policy);
> if (ret) {
> dprintk("initialization failed\n");
>- goto err_out;
>+ goto err_unlock_policy;
> }
> policy->user_policy.min = policy->min;
> policy->user_policy.max = policy->max;
>@@ -860,15 +862,21 @@ static int cpufreq_add_dev(struct sys_de
> /* Check for existing affected CPUs.
> * They may not be aware of it due to CPU Hotplug.
> */
>- managed_policy = cpufreq_cpu_get(j);
>/* FIXME: Where is this released? What about error paths? */
>+ managed_policy = cpufreq_cpu_get(j);
> if (unlikely(managed_policy)) {
>
> /* Set proper policy_cpu */
> unlock_policy_rwsem_write(cpu);
> per_cpu(policy_cpu, cpu) = managed_policy->cpu;
>
>- if (lock_policy_rwsem_write(cpu) < 0)
>- goto err_out_driver_exit;
>+ if (lock_policy_rwsem_write(cpu) < 0) {
>+ /* Should not go through policy
>unlock path */
>+ if (cpufreq_driver->exit)
>+ cpufreq_driver->exit(policy);
>+ ret = -EBUSY;
>+ cpufreq_cpu_put(managed_policy);
>+ goto err_free_cpumask;
>+ }
>
> spin_lock_irqsave(&cpufreq_driver_lock, flags);
> cpumask_copy(managed_policy->cpus,
>policy->cpus);
>@@ -879,12 +887,14 @@ static int cpufreq_add_dev(struct sys_de
> ret = sysfs_create_link(&sys_dev->kobj,
> &managed_policy->kobj,
> "cpufreq");
>- if (ret)
>- goto err_out_driver_exit;
>-
>- cpufreq_debug_enable_ratelimit();
>- ret = 0;
>- goto err_out_driver_exit; /* call
>driver->exit() */
>+ if (!ret)
>+ cpufreq_cpu_put(managed_policy);
Looks like cpufreq_cpu_put is needed both with ret and !ret. No?
Thanks,
Venki
>+ /*
>+ * Success. We only needed to be added
>to the mask.
>+ * Call driver->exit() because only the
>cpu parent of
>+ * the kobj needed to call init().
>+ */
>+ goto out_driver_exit; /* call driver->exit() */
> }
> }
> #endif
>@@ -894,25 +904,25 @@ static int cpufreq_add_dev(struct sys_de
> ret = kobject_init_and_add(&policy->kobj,
>&ktype_cpufreq, &sys_dev->kobj,
> "cpufreq");
> if (ret)
>- goto err_out_driver_exit;
>+ goto out_driver_exit;
>
> /* set up files for this cpu device */
> drv_attr = cpufreq_driver->attr;
> while ((drv_attr) && (*drv_attr)) {
> ret = sysfs_create_file(&policy->kobj,
>&((*drv_attr)->attr));
> if (ret)
>- goto err_out_driver_exit;
>+ goto err_out_kobj_put;
> drv_attr++;
> }
> if (cpufreq_driver->get) {
> ret = sysfs_create_file(&policy->kobj,
>&cpuinfo_cur_freq.attr);
> if (ret)
>- goto err_out_driver_exit;
>+ goto err_out_kobj_put;
> }
> if (cpufreq_driver->target) {
> ret = sysfs_create_file(&policy->kobj,
>&scaling_cur_freq.attr);
> if (ret)
>- goto err_out_driver_exit;
>+ goto err_out_kobj_put;
> }
>
> spin_lock_irqsave(&cpufreq_driver_lock, flags);
>@@ -930,12 +940,14 @@ static int cpufreq_add_dev(struct sys_de
> continue;
>
> dprintk("CPU %u already managed, adding link\n", j);
>- cpufreq_cpu_get(cpu);
>+ managed_policy = cpufreq_cpu_get(cpu);
> cpu_sys_dev = get_cpu_sysdev(j);
> ret = sysfs_create_link(&cpu_sys_dev->kobj,
>&policy->kobj,
> "cpufreq");
>- if (ret)
>+ if (ret) {
>+ cpufreq_cpu_put(managed_policy);
> goto err_out_unregister;
>+ }
> }
>
> policy->governor = NULL; /* to assure that the starting
>sequence is
>@@ -967,17 +979,20 @@ err_out_unregister:
> per_cpu(cpufreq_cpu_data, j) = NULL;
> spin_unlock_irqrestore(&cpufreq_driver_lock, flags);
>
>+err_out_kobj_put:
> kobject_put(&policy->kobj);
> wait_for_completion(&policy->kobj_unregister);
>
>-err_out_driver_exit:
>+out_driver_exit:
> if (cpufreq_driver->exit)
> cpufreq_driver->exit(policy);
>
>-err_out:
>+err_unlock_policy:
> unlock_policy_rwsem_write(cpu);
>+err_free_cpumask:
>+ free_cpumask_var(policy->cpus);
>+err_free_policy:
> kfree(policy);
>-
> nomem_out:
> module_put(cpufreq_driver->owner);
> module_out:
>
--
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