On Tuesday, November 27, 2012 10:19:29 PM Rafael J. Wysocki wrote:
> On Saturday, November 24, 2012 08:59:14 PM Ming Lei wrote:
> > The patch introduces the flag of memalloc_noio in 'struct dev_pm_info'
> > to help PM core to teach mm not allocating memory with GFP_KERNEL
> > flag for avoiding probable deadlock.
> >
> > As explained in the comment, any GFP_KERNEL allocation inside
> > runtime_resume() or runtime_suspend() on any one of device in
> > the path from one block or network device to the root device
> > in the device tree may cause deadlock, the introduced
> > pm_runtime_set_memalloc_noio() sets or clears the flag on
> > device in the path recursively.
> >
> > Cc: Alan Stern <stern@xxxxxxxxxxxxxxxxxxx>
> > Cc: "Rafael J. Wysocki" <rjw@xxxxxxx>
> > Signed-off-by: Ming Lei <ming.lei@xxxxxxxxxxxxx>
> > ---
> > v5:
> > - fix code style error
> > - add comment on clear the device memalloc_noio flag
> > v4:
> > - rename memalloc_noio_resume as memalloc_noio
> > - remove pm_runtime_get_memalloc_noio()
> > - add comments on pm_runtime_set_memalloc_noio
> > v3:
> > - introduce pm_runtime_get_memalloc_noio()
> > - hold one global lock on pm_runtime_set_memalloc_noio
> > - hold device power lock when accessing memalloc_noio_resume
> > flag suggested by Alan Stern
> > - implement pm_runtime_set_memalloc_noio without recursion
> > suggested by Alan Stern
> > v2:
> > - introduce pm_runtime_set_memalloc_noio()
> > ---
> > drivers/base/power/runtime.c | 60 ++++++++++++++++++++++++++++++++++++++++++
> > include/linux/pm.h | 1 +
> > include/linux/pm_runtime.h | 3 +++
> > 3 files changed, 64 insertions(+)
> >
> > diff --git a/drivers/base/power/runtime.c b/drivers/base/power/runtime.c
> > index 3148b10..3e198a0 100644
> > --- a/drivers/base/power/runtime.c
> > +++ b/drivers/base/power/runtime.c
> > @@ -124,6 +124,66 @@ unsigned long pm_runtime_autosuspend_expiration(struct device *dev)
> > }
> > EXPORT_SYMBOL_GPL(pm_runtime_autosuspend_expiration);
> >
> > +static int dev_memalloc_noio(struct device *dev, void *data)
> > +{
> > + return dev->power.memalloc_noio;
> > +}
> > +
> > +/*
> > + * pm_runtime_set_memalloc_noio - Set a device's memalloc_noio flag.
> > + * @dev: Device to handle.
> > + * @enable: True for setting the flag and False for clearing the flag.
> > + *
> > + * Set the flag for all devices in the path from the device to the
> > + * root device in the device tree if @enable is true, otherwise clear
> > + * the flag for devices in the path whose siblings don't set the flag.
> > + *
>
> Please use counters instead of walking the whole path every time. Ie. in
> addition to the flag add a counter to store the number of the device's
> children having that flag set.
I would use the flag only to store the information that
pm_runtime_set_memalloc_noio(dev, true) has been run for this device directly
and I'd use a counter for everything else.
That is, have power.memalloc_count that would be incremented when (1)
pm_runtime_set_memalloc_noio(dev, true) is called for that device and (2) when
power.memalloc_count for one of its children changes from 0 to 1 (and
analogously for decrementation). Then, check the counter in rpm_callback().
Thanks,
Rafael
--
I speak only for myself.
Rafael J. Wysocki, Intel Open Source Technology Center.
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