Messages in this thread | | | Date | Thu, 21 Feb 2008 11:27:54 -0500 (EST) | From | Alan Stern <> | Subject | Re: [Bug 10030] Suspend doesn't work when SD card is inserted |
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On Thu, 21 Feb 2008, Rafael J. Wysocki wrote:
> > > +bool in_suspend_context(void) > > > +{ > > > + bool result; > > > + > > > + mutex_lock(&suspending_task_mtx); > > > + result = (suspending_task == current); > > > + mutex_unlock(&suspending_task_mtx); > > > + return result; > > > +} > > > > If suspending_task == current then you are guaranteed to be serialized, > > because everything a single task does is serial. > > As I said before (but that doesn't seem to reach the list, so I'm repeating), > this is to protect other tasks from reading an inconsistent value of > suspending_task in case they attempt to remove a device concurrently with > respect to us. > > While this is not likely to happen right now, because of the freezer, it may > very well happen when the freezer is finally removed.
Sorry, I don't understand. Are you worried that process A might set suspending_task = A but then process B might still see suspending_task == NULL? Or that A might set suspend_task = NULL but then B might still see suspending_task == A?
Neither one will cause any problem, since the only case that matters is when B sees suspending_task == B -- and that can happen if and only if B was the last process to set suspending_task.
In fact, you might as well get rid of the set_suspending_task() routine entirely and just put the assignments inline.
> --- linux-2.6.orig/drivers/base/core.c > +++ linux-2.6/drivers/base/core.c > @@ -929,6 +929,11 @@ void device_del(struct device *dev) > struct device *parent = dev->parent; > struct class_interface *class_intf; > > + if (in_suspend_context()) { > + get_device(dev);
Where is this get_device() undone? Shouldn't there be an extra put_device() added to unregister_dropped_devices()?
> + device_pm_schedule_removal(dev); > + return; > + } > device_pm_remove(dev); > if (parent) > klist_del(&dev->knode_parent);
And now the change to device_destroy() isn't needed at all.
Alan Stern
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