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Date: Wed, 14 Mar 2012 12:21:31 -0700
From: Stephen Boyd <sboyd@...eaurora.org>
To: "Rafael J. Wysocki" <rjw@...k.pl>
CC: Saravana Kannan <skannan@...eaurora.org>,
Kay Sievers <kay.sievers@...y.org>,
Greg KH <gregkh@...uxfoundation.org>,
Christian Lamparter <chunkeey@...glemail.com>,
linux-kernel@...r.kernel.org,
"Srivatsa S. Bhat" <srivatsa.bhat@...ux.vnet.ibm.com>,
alan@...rguk.ukuu.org.uk,
Linus Torvalds <torvalds@...ux-foundation.org>,
Linux PM mailing list <linux-pm@...r.kernel.org>
Subject: Re: [PATCH] firmware loader: don't cancel _nowait requests when helper
is not yet available
On 03/13/12 13:14, Rafael J. Wysocki wrote:
> All of those use cases are in fact of the "wait for user space to be thawed
> and then load the firmware" type, which I believe may be handled without
> changing that code.
>
> Why don't you make your kthread freezable, for one example?
>
> Why don't you use a freezable workqueue instead?
>
If we put it on the freezable workqueue or make it a freezable thread
will it work?
In my scenario a wakeup interrupt comes in that wakes us up from
suspend. Within that wakeup handler a work item is scheduled to the
freezable workqueue. That work item then calls request_firmware().
It looks like we call schedule() after thawing the workqueues and tasks
so the work item could run before usermodehelpers are enabled and then
request_firmware() would fail. Do we need something like this (ignore
the fact that we call usermodhelper_enable() twice)?
diff --git a/kernel/power/process.c b/kernel/power/process.c
index 7e42645..61bfa95 100644
--- a/kernel/power/process.c
+++ b/kernel/power/process.c
@@ -187,6 +187,7 @@ void thaw_processes(void)
} while_each_thread(g, p);
read_unlock(&tasklist_lock);
+ usermodehelper_enable();
schedule();
printk("done.\n");
}
Is there a reason we disable usermodehelpers if
CONFIG_SUSPEND_FREEZER=n? Should we do this instead so that
usermodehelpers are only disabled if we freeze userspace? Also what is
that schedule() call in thaw_kernel_threads() for? It looks like we'll
call schedule between kernel thread thawing and userspace thawing. I
pushed out the schedule() call to the callers so that we don't call
schedule() until userspace is thawed.
diff --git a/kernel/power/process.c b/kernel/power/process.c
index 7e42645..8fae228 100644
--- a/kernel/power/process.c
+++ b/kernel/power/process.c
@@ -125,6 +125,7 @@ int freeze_processes(void)
if (!pm_freezing)
atomic_inc(&system_freezing_cnt);
+ usermodehelper_disable();
printk("Freezing user space processes ... ");
pm_freezing = true;
error = try_to_freeze_tasks(true);
@@ -187,6 +188,7 @@ void thaw_processes(void)
} while_each_thread(g, p);
read_unlock(&tasklist_lock);
+ usermodehelper_enable();
schedule();
printk("done.\n");
}
@@ -207,6 +209,5 @@ void thaw_kernel_threads(void)
} while_each_thread(g, p);
read_unlock(&tasklist_lock);
- schedule();
printk("done.\n");
}
diff --git a/kernel/power/suspend.c b/kernel/power/suspend.c
index 4fd51be..1ab3e59 100644
--- a/kernel/power/suspend.c
+++ b/kernel/power/suspend.c
@@ -101,17 +101,12 @@ static int suspend_prepare(void)
if (error)
goto Finish;
- error = usermodehelper_disable();
- if (error)
- goto Finish;
-
error = suspend_freeze_processes();
if (!error)
return 0;
suspend_stats.failed_freeze++;
dpm_save_failed_step(SUSPEND_FREEZE);
- usermodehelper_enable();
Finish:
pm_notifier_call_chain(PM_POST_SUSPEND);
pm_restore_console();
@@ -259,7 +254,6 @@ int suspend_devices_and_enter(suspend_state_t state)
static void suspend_finish(void)
{
suspend_thaw_processes();
- usermodehelper_enable();
pm_notifier_call_chain(PM_POST_SUSPEND);
pm_restore_console();
}
diff --git a/kernel/power/user.c b/kernel/power/user.c
index 3e10007..1a8fd6f 100644
--- a/kernel/power/user.c
+++ b/kernel/power/user.c
@@ -222,14 +222,8 @@ static long snapshot_ioctl(struct file *filp, unsigned int cmd,
sys_sync();
printk("done.\n");
- error = usermodehelper_disable();
- if (error)
- break;
-
error = freeze_processes();
- if (error)
- usermodehelper_enable();
- else
+ if (!error)
data->frozen = 1;
break;
@@ -238,7 +232,6 @@ static long snapshot_ioctl(struct file *filp, unsigned int cmd,
break;
pm_restore_gfp_mask();
thaw_processes();
- usermodehelper_enable();
data->frozen = 0;
break;
@@ -251,6 +244,7 @@ static long snapshot_ioctl(struct file *filp, unsigned int cmd,
error = hibernation_snapshot(data->platform_support);
if (error) {
thaw_kernel_threads();
+ schedule();
} else {
error = put_user(in_suspend, (int __user *)arg);
if (!error && !freezer_test_done)
@@ -258,6 +252,7 @@ static long snapshot_ioctl(struct file *filp, unsigned int cmd,
if (freezer_test_done) {
freezer_test_done = false;
thaw_kernel_threads();
+ schedule();
}
}
break;
@@ -285,6 +280,7 @@ static long snapshot_ioctl(struct file *filp, unsigned int cmd,
* might fail or even deadlock).
*/
thaw_kernel_threads();
+ schedule();
break;
case SNAPSHOT_PREF_IMAGE_SIZE:
--
Sent by an employee of the Qualcomm Innovation Center, Inc.
The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum.
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