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SubjectRe: [PATCH v21 015/100] cgroup freezer: Update stale locking comments

On 05/06/2010 03:40 PM, Rafael J. Wysocki wrote:
> On Saturday 01 May 2010, Oren Laadan wrote:
>> From: Matt Helsley <matthltc@us.ibm.com>
>>
>> Update stale comments regarding locking order and add a little more detail
>> so it's easier to follow the locking between the cgroup freezer and the
>> power management freezer code.
>
> I guess these three patches are for me.
>
> Do you want me to handle them?

Yes, please, that would be great.

Thanks,

Oren.

>
> Rafael
>
>
>> Signed-off-by: Matt Helsley <matthltc@us.ibm.com>
>> Cc: Oren Laadan <orenl@cs.columbia.edu>
>> Cc: Cedric Le Goater <legoater@free.fr>
>> Cc: Paul Menage <menage@google.com>
>> Cc: Li Zefan <lizf@cn.fujitsu.com>
>> Cc: Rafael J. Wysocki <rjw@sisk.pl>
>> Cc: linux-pm@lists.linux-foundation.org
>> ---
>> kernel/cgroup_freezer.c | 21 +++++++++++++--------
>> 1 files changed, 13 insertions(+), 8 deletions(-)
>>
>> diff --git a/kernel/cgroup_freezer.c b/kernel/cgroup_freezer.c
>> index da5e139..85f19cc 100644
>> --- a/kernel/cgroup_freezer.c
>> +++ b/kernel/cgroup_freezer.c
>> @@ -89,10 +89,10 @@ struct cgroup_subsys freezer_subsys;
>>
>> /* Locks taken and their ordering
>> * ------------------------------
>> - * css_set_lock
>> * cgroup_mutex (AKA cgroup_lock)
>> - * task->alloc_lock (AKA task_lock)
>> * freezer->lock
>> + * css_set_lock
>> + * task->alloc_lock (AKA task_lock)
>> * task->sighand->siglock
>> *
>> * cgroup code forces css_set_lock to be taken before task->alloc_lock
>> @@ -100,33 +100,38 @@ struct cgroup_subsys freezer_subsys;
>> * freezer_create(), freezer_destroy():
>> * cgroup_mutex [ by cgroup core ]
>> *
>> - * can_attach():
>> - * cgroup_mutex
>> + * freezer_can_attach():
>> + * cgroup_mutex (held by caller of can_attach)
>> *
>> - * cgroup_frozen():
>> + * cgroup_freezing_or_frozen():
>> * task->alloc_lock (to get task's cgroup)
>> *
>> * freezer_fork() (preserving fork() performance means can't take cgroup_mutex):
>> - * task->alloc_lock (to get task's cgroup)
>> * freezer->lock
>> * sighand->siglock (if the cgroup is freezing)
>> *
>> * freezer_read():
>> * cgroup_mutex
>> * freezer->lock
>> + * write_lock css_set_lock (cgroup iterator start)
>> + * task->alloc_lock
>> * read_lock css_set_lock (cgroup iterator start)
>> *
>> * freezer_write() (freeze):
>> * cgroup_mutex
>> * freezer->lock
>> + * write_lock css_set_lock (cgroup iterator start)
>> + * task->alloc_lock
>> * read_lock css_set_lock (cgroup iterator start)
>> - * sighand->siglock
>> + * sighand->siglock (fake signal delivery inside freeze_task())
>> *
>> * freezer_write() (unfreeze):
>> * cgroup_mutex
>> * freezer->lock
>> + * write_lock css_set_lock (cgroup iterator start)
>> + * task->alloc_lock
>> * read_lock css_set_lock (cgroup iterator start)
>> - * task->alloc_lock (to prevent races with freeze_task())
>> + * task->alloc_lock (inside thaw_process(), prevents race with refrigerator())
>> * sighand->siglock
>> */
>> static struct cgroup_subsys_state *freezer_create(struct cgroup_subsys *ss,
>>
>
>


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