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SubjectRe: [linux-pm] [PATCH] Workqueue freezer support.
From
Date
Hi.

On Fri, 2005-07-22 at 05:42, Patrick Mochel wrote:
> On Thu, 21 Jul 2005, Nigel Cunningham wrote:
>
> > This patch implements freezer support for workqueues. The current
> > refrigerator implementation makes all workqueues NOFREEZE, regardless of
> > whether they need to be or not.
>
> A few comments..
>
> > Signed-off by: Nigel Cunningham <nigel@suspend2.net>
> >
> > drivers/acpi/osl.c | 2 +-
> > drivers/block/ll_rw_blk.c | 2 +-
> > drivers/char/hvc_console.c | 2 +-
> > drivers/char/hvcs.c | 2 +-
> > drivers/input/serio/serio.c | 2 +-
> > drivers/md/dm-crypt.c | 2 +-
> > drivers/scsi/hosts.c | 2 +-
> > drivers/usb/net/pegasus.c | 2 +-
>
> If you want some practice splitting things up, submit the patches above
> individually to the maintainers o the relevant code once the patches you
> submit below get merged to -mm.

Ok. Thanks for telling me.

> > include/linux/kthread.h | 20 ++++++++++++++++++--
> > include/linux/workqueue.h | 9 ++++++---
> > kernel/kmod.c | 4 ++++
> > kernel/kthread.c | 23 ++++++++++++++++++++++-
> > kernel/sched.c | 4 ++--
> > kernel/softirq.c | 3 +--
> > kernel/workqueue.c | 21 ++++++++++++---------
> > 15 files changed, 73 insertions(+), 27 deletions(-)
>
>
> You should make sure that you get an explicit ACK from people (Ingo et al)
> about whether this is an acceptable interface.

Ok. How do I know who to ask? (Who besides Ingo, and could I learn who
without help - Maintainers?)

> > --- 400-workthreads.patch-old/include/linux/kthread.h 2004-11-03 21:51:12.000000000 +1100
> > +++ 400-workthreads.patch-new/include/linux/kthread.h 2005-07-20 15:11:37.000000000 +1000
> > @@ -27,6 +27,14 @@ struct task_struct *kthread_create(int (
> > void *data,
> > const char namefmt[], ...);
> >
> > +struct task_struct *_kthread_create(int (*threadfn)(void *data),
> > + void *data,
> > + unsigned long freezer_flags,
> > + const char namefmt[], ...);
> > +
>
> This should be __kthread_create(...)

Ok. Fixed. Is one underscore ever right?

> > -#define kthread_run(threadfn, data, namefmt, ...) \
> > +#define kthread_run(threadfn, data, namefmt, args...) \
> > ({ \
> > struct task_struct *__k \
> > - = kthread_create(threadfn, data, namefmt, ## __VA_ARGS__); \
> > + = kthread_create(threadfn, data, namefmt, ##args); \
> > if (!IS_ERR(__k)) \
> > wake_up_process(__k); \
> > __k; \
> > })
> >
> > +#define kthread_nofreeze_run(threadfn, data, namefmt, args...) \
> > +({ \
> > + struct task_struct *__k = kthread_nofreeze_create(threadfn, data, \
> > + namefmt, ##args); \
> > + if (!IS_ERR(__k)) \
> > + wake_up_process(__k); \
> > + __k; \
> > +})
>
> Do these functions need to be inlined?

I tried to find out how to pass the va_list on nicely without using a
#define, but could find the info. If you're able to tell me, I'll make
them inline. Perhaps I could also improve the kthread_create call Pavel
and Ingo commented on.

> > @@ -86,6 +87,10 @@ static int kthread(void *_create)
> > /* By default we can run anywhere, unlike keventd. */
> > set_cpus_allowed(current, CPU_MASK_ALL);
> >
> > + /* Set our freezer flags */
> > + current->flags &= ~(PF_SYNCTHREAD | PF_NOFREEZE);
> > + current->flags |= (create->freezer_flags & PF_NOFREEZE);
> > +
>
> Maybe these should be encapsulated in a helper in include/linux/sched.h
> like some other flags manipulations are?

This would be the only place it's used. Does that matter? (And note from
the updated patch that the SYNCTHREAD wouldn't be there).

> > diff -ruNp 400-workthreads.patch-old/kernel/sched.c 400-workthreads.patch-new/kernel/sched.c
> > --- 400-workthreads.patch-old/kernel/sched.c 2005-07-21 04:00:02.000000000 +1000
> > +++ 400-workthreads.patch-new/kernel/sched.c 2005-07-21 04:00:19.000000000 +1000
> > @@ -4580,10 +4580,10 @@ static int migration_call(struct notifie
> >
> > switch (action) {
> > case CPU_UP_PREPARE:
> > - p = kthread_create(migration_thread, hcpu, "migration/%d",cpu);
> > + p = kthread_create(migration_thread, hcpu,
> > + "migration/%d",cpu);
>
> This is unnecessary.

Oops. Comes from adding an extra parameter, fixing line length and then
removing it. Fixed.

> Overall, it looks pretty good.

Thanks!

Nigel

> Thanks,
>
>
>
> Pat
--
Evolution.
Enumerate the requirements.
Consider the interdependencies.
Calculate the probabilities.

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