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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: Paul Parsons <lost.distance@yahoo.com>
Acked-by: Rafael J. Wysocki <rjw@sisk.pl>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>
hifive-unleashed-5.1
Paul Parsons 2011-05-13 02:46:03 +01:00 committed by Jiri Kosina
parent 81024fc41a
commit fda5fe1972
1 changed files with 0 additions and 5 deletions
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5
drivers/char/apm-emulation.c
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@ -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;
}