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Commit fda5fe19 authored by Paul Parsons's avatar Paul Parsons Committed by Jiri Kosina
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apm-emulation: apm_mutex breaks ACK; remove it 



apm_mutex is locked by a process (e.g. apm -s) at the start of apm_ioctl() and
remains locked while pm_suspend() is called. Any subsequent process trying to
ACK the suspend (e.g. apmd) is then blocked at the start of apm_ioctl(),
causing the suspend to be delayed for 5 seconds in apm_suspend_notifier()
while the ACK times out. In short, ACKs don't work.

The driver's data structures are sufficiently protected by assorted locks. And
pm_suspend() has its own mutex to prevent reentrancy. Consequently there is no
obvious requirement for apm_mutex, which evolved from earlier BKL calls. So
let's remove it.

Signed-off-by: default avatarPaul Parsons <lost.distance@yahoo.com>
Acked-by: default avatarRafael J. Wysocki <rjw@sisk.pl>
Signed-off-by: default avatarJiri Kosina <jkosina@suse.cz>
parent 81024fc4

drivers/char/apm-emulation.c

+0 −5
Original line number Diff line number Diff line
@@ -126,7 +126,6 @@ struct apm_user { 
/*

 * Local variables

 */

static DEFINE_MUTEX(apm_mutex);

static atomic_t suspend_acks_pending = ATOMIC_INIT(0);

static atomic_t userspace_notification_inhibit = ATOMIC_INIT(0);

static int apm_disabled;
@@ -275,7 +274,6 @@ apm_ioctl(struct file *filp, u_int cmd, u_long arg) 
	if (!as->suser || !as->writer)

		return -EPERM;



	mutex_lock(&apm_mutex);

	switch (cmd) {

	case APM_IOC_SUSPEND:

		mutex_lock(&state_lock);
@@ -336,7 +334,6 @@ apm_ioctl(struct file *filp, u_int cmd, u_long arg) 
		mutex_unlock(&state_lock);

		break;

	}

	mutex_unlock(&apm_mutex);



	return err;

}
@@ -371,7 +368,6 @@ static int apm_open(struct inode * inode, struct file * filp) 
{

	struct apm_user *as;



	mutex_lock(&apm_mutex);

	as = kzalloc(sizeof(*as), GFP_KERNEL);

	if (as) {

		/*
@@ -391,7 +387,6 @@ static int apm_open(struct inode * inode, struct file * filp) 


		filp->private_data = as;

	}

	mutex_unlock(&apm_mutex);



	return as ? 0 : -ENOMEM;

}