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    SubjectRe: [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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