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Message-ID: <4EB677CB.20608@linux.vnet.ibm.com>
Date: Sun, 06 Nov 2011 17:34:27 +0530
From: "Srivatsa S. Bhat" <srivatsa.bhat@...ux.vnet.ibm.com>
To: Tejun Heo <tj@...nel.org>
CC: rjw@...k.pl, paul@...lmenage.org, linux-kernel@...r.kernel.org,
linux-pm@...r.kernel.org, arnd@...db.de, oleg@...hat.com,
matthltc@...ibm.com, Paul Menage <menage@...gle.com>
Subject: Re: [PATCH 05/17] freezer: rename thaw_process() to __thaw_task()
and simplify the implementation
On 11/01/2011 12:35 AM, Tejun Heo wrote:
> thaw_process() now has only internal users - system and cgroup
> freezers. Remove the unnecessary return value, rename, unexport and
> collapse __thaw_process() into it. This will help further updates to
> the freezer code.
>
> -v2: minor style update as suggested by Matt.
>
> Signed-off-by: Tejun Heo <tj@...nel.org>
> Cc: Paul Menage <menage@...gle.com>
> Cc: Matt Helsley <matthltc@...ibm.com>
> ---
> include/linux/freezer.h | 3 +--
> kernel/cgroup_freezer.c | 7 +++----
> kernel/freezer.c | 31 ++++++++++++-------------------
> kernel/power/process.c | 2 +-
> 4 files changed, 17 insertions(+), 26 deletions(-)
>
> diff --git a/include/linux/freezer.h b/include/linux/freezer.h
> index 4a73dd2..253bcfe 100644
> --- a/include/linux/freezer.h
> +++ b/include/linux/freezer.h
> @@ -45,7 +45,7 @@ static inline bool should_send_signal(struct task_struct *p)
> }
>
> /* Takes and releases task alloc lock using task_lock() */
> -extern int thaw_process(struct task_struct *p);
> +extern void __thaw_task(struct task_struct *t);
>
> extern bool __refrigerator(bool check_kthr_stop);
> extern int freeze_processes(void);
> @@ -183,7 +183,6 @@ static inline int frozen(struct task_struct *p) { return 0; }
> static inline int freezing(struct task_struct *p) { return 0; }
> static inline void set_freeze_flag(struct task_struct *p) {}
> static inline void clear_freeze_flag(struct task_struct *p) {}
> -static inline int thaw_process(struct task_struct *p) { return 1; }
>
> static inline bool __refrigerator(bool check_kthr_stop) { return false; }
> static inline int freeze_processes(void) { return -ENOSYS; }
> diff --git a/kernel/cgroup_freezer.c b/kernel/cgroup_freezer.c
> index e691818..e7fa0ec 100644
> --- a/kernel/cgroup_freezer.c
> +++ b/kernel/cgroup_freezer.c
> @@ -130,7 +130,7 @@ struct cgroup_subsys freezer_subsys;
> * write_lock css_set_lock (cgroup iterator start)
> * task->alloc_lock
> * read_lock css_set_lock (cgroup iterator start)
> - * task->alloc_lock (inside thaw_process(), prevents race with refrigerator())
> + * task->alloc_lock (inside __thaw_task(), prevents race with refrigerator())
^^^^^^^^^
Shouldn't this be __refrigerator()?
> * sighand->siglock
> */
> static struct cgroup_subsys_state *freezer_create(struct cgroup_subsys *ss,
> @@ -300,9 +300,8 @@ static void unfreeze_cgroup(struct cgroup *cgroup, struct freezer *freezer)
> struct task_struct *task;
>
> cgroup_iter_start(cgroup, &it);
> - while ((task = cgroup_iter_next(cgroup, &it))) {
> - thaw_process(task);
> - }
> + while ((task = cgroup_iter_next(cgroup, &it)))
> + __thaw_task(task);
> cgroup_iter_end(cgroup, &it);
>
> freezer->state = CGROUP_THAWED;
> diff --git a/kernel/freezer.c b/kernel/freezer.c
> index 57ba75f..8faa0e0 100644
> --- a/kernel/freezer.c
> +++ b/kernel/freezer.c
> @@ -145,18 +145,8 @@ void cancel_freezing(struct task_struct *p)
> }
> }
>
> -static int __thaw_process(struct task_struct *p)
> -{
> - if (frozen(p)) {
> - p->flags &= ~PF_FROZEN;
> - return 1;
> - }
> - clear_freeze_flag(p);
> - return 0;
> -}
> -
> /*
> - * Wake up a frozen process
> + * Wake up a frozen task
> *
> * task_lock() is needed to prevent the race with refrigerator() which may
^^^^^^
__refrigerator()?
> * occur if the freezing of tasks fails. Namely, without the lock, if the
> @@ -164,15 +154,18 @@ static int __thaw_process(struct task_struct *p)
> * refrigerator() could call frozen_process(), in which case the task would be
> * frozen and no one would thaw it.
> */
> -int thaw_process(struct task_struct *p)
> +void __thaw_task(struct task_struct *p)
> {
> + bool was_frozen;
> +
> task_lock(p);
> - if (__thaw_process(p) == 1) {
> - task_unlock(p);
> - wake_up_process(p);
> - return 1;
> - }
> + was_frozen = frozen(p);
> + if (was_frozen)
> + p->flags &= ~PF_FROZEN;
> + else
> + clear_freeze_flag(p);
> task_unlock(p);
> - return 0;
> +
> + if (was_frozen)
> + wake_up_process(p);
> }
> -EXPORT_SYMBOL(thaw_process);
> diff --git a/kernel/power/process.c b/kernel/power/process.c
> index addbbe5..fe27872 100644
> --- a/kernel/power/process.c
> +++ b/kernel/power/process.c
> @@ -186,7 +186,7 @@ static void thaw_tasks(bool nosig_only)
> if (cgroup_freezing_or_frozen(p))
> continue;
>
> - thaw_process(p);
> + __thaw_task(p);
> } while_each_thread(g, p);
> read_unlock(&tasklist_lock);
> }
Rebasing to latest kernel, we need to do the conversion in mm/oom_kill.c as well,
(and consequently add __thaw_task() empty function under !CONFIG_FREEZER, in
include/linux/freezer.h)
Thanks,
Srivatsa S. Bhat
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