Re: [linux-pm] [PATCH 0/8] Suspend block api (version 8)

Florian Mickler
2010-06-01T07:07:50Z

On Mon, 31 May 2010 16:26:17 -0700
mark gross <640e9920@gmail.com> wrote:

> On Mon, May 31, 2010 at 11:38:55PM +0200, Rafael J. Wysocki wrote:
> > On Monday 31 May 2010, Arve Hjønnevåg wrote:
> > > 2010/5/29 Alan Stern <stern@rowland.harvard.edu>:
> > > > On Sat, 29 May 2010, Arve Hjønnevåg wrote:
> > > >
> > > >> > In place of in-kernel suspend blockers, there will be a new type of QoS
> > > >> > constraint -- call it QOS_EVENTUALLY. It's a very weak constraint,
> > > >> > compatible with all cpuidle modes in which runnable threads are allowed
> > > >> > to run (which is all of them), but not compatible with suspend.
> > > >> >
> > > >> This sound just like another API rename. It will work, but given that
> > > >> suspend blockers was the name least objectionable last time around,
> > > >> I'm not sure what this would solve.
> > > >
> > > > It's not just a rename. By changing this into a QoS constraint, we
> > > > make it more generally useful. Instead of standing on its own, it
> > > > becomes part of the PM-QOS framework.
> > > >
> > >
> > > We cannot use the existing pm-qos framework. It is not safe to call
> > > from atomic context.
> >
> > We've just merged a patch that fixed that if I'm not mistaken. Mark, did your
> > PM QoS update fix that?
> >
>
> I'm pretty sure it can be called in atomic context, and if its not I'm
> sure we can fix that. It can be called in atomic context. I don't
> think it was ever a problem to call it in atomic context. The problem it
> had was that crappy list of string compares. Thats been fixed.
>
> --mgross
>

Well, the register call uses kzalloc. Apart from that I
think we're good.

The outstanding list traversals can be fixed also. (see below)

Cheers,
Flo

>From 66fdd76f8cc4be722dba3859ddadfe07e7a4b755 Mon Sep 17 00:00:00 2001
From: Florian Mickler <florian@mickler.org>
Date: Tue, 1 Jun 2010 09:04:26 +0200
Subject: [PATCH] pm_qos: remove unnecessary list-traversal

The new extreme_value is only depending on the old extreme_value and
the changing value.

Signed-off-by: Florian Mickler <florian@mickler.org>
---
kernel/pm_qos_params.c | 20 ++++++++++++++------
1 files changed, 14 insertions(+), 6 deletions(-)

diff --git a/kernel/pm_qos_params.c b/kernel/pm_qos_params.c
index f42d3f7..6618e2c 100644
--- a/kernel/pm_qos_params.c
+++ b/kernel/pm_qos_params.c
@@ -136,6 +136,16 @@ static s32 min_compare(s32 v1, s32 v2)
}

+static void update_target_val(int pm_qos_class, s32 val)
+{
+ s32 extreme_value;
+ s32 new_value;
+ extreme_value = atomic_read(&pm_qos_array[pm_qos_class]->target_value);
+ new_value = pm_qos_array[pm_qos_class]->comparitor(val,extreme_value);
+ if (extreme_value != new_value)
+ atomic_set(&pm_qos_array[pm_qos_class]->target_value,new_value);
+}
+
static void update_target(int pm_qos_class)
{
s32 extreme_value;
@@ -227,8 +237,8 @@ struct pm_qos_request_list *pm_qos_add_request(int pm_qos_class, s32 value)
spin_lock_irqsave(&pm_qos_lock, flags);
list_add(&dep->list,
&pm_qos_array[pm_qos_class]->requests.list);
+ update_target_val(pm_qos_class,dep->value);
spin_unlock_irqrestore(&pm_qos_lock, flags);
- update_target(pm_qos_class);
}

return dep;
@@ -249,23 +259,21 @@ void pm_qos_update_request(struct pm_qos_request_list *pm_qos_req,
s32 new_value)
{
unsigned long flags;
- int pending_update = 0;
s32 temp;

if (pm_qos_req) { /*guard against callers passing in null */
+ int target = pm_qos_req->pm_qos_class;
spin_lock_irqsave(&pm_qos_lock, flags);
if (new_value == PM_QOS_DEFAULT_VALUE)
- temp = pm_qos_array[pm_qos_req->pm_qos_class]->default_value;
+ temp = pm_qos_array[target]->default_value;
else
temp = new_value;

if (temp != pm_qos_req->value) {
- pending_update = 1;
pm_qos_req->value = temp;
+ update_target_val(target,temp);
}
spin_unlock_irqrestore(&pm_qos_lock, flags);
- if (pending_update)
- update_target(pm_qos_req->pm_qos_class);
}
}
EXPORT_SYMBOL_GPL(pm_qos_update_request);
--
1.7.1