On Monday 15 of October 2012 15:39:49 Yanmin Zhang wrote: > On Fri, 2012-09-21 at 01:58 +0000, Zhang, LongX wrote: > > From: LongX Zhang <longx.zhang@xxxxxxxxx> > > > > device_pm_remove will call pm_runtime_remove which would disable > > runtime PM of the device. After that pm_runtime_get* or > > pm_runtime_put* will be ingored. So if we disable the runtime PM > > before device really be removed, drivers' _remove callback may > > access HW even pm_runtime_get* fails. That is bad. > The background about the patch: We hit an hang issue when removing a mmc > device on Medfield Android phone by sysfs interface. > > Consider below call sequence when removing a device: > device_del => device_pm_remove > => class_intf->remove_dev(dev, class_intf) => pm_runtime_get_sync/put_sync > => bus_remove_device => device_release_driver => pm_runtime_get_sync/put_sync > > remove_dev might call pm_runtime_get_sync/put_sync. > Then, generic device_release_driver also calls pm_runtime_get_sync/put_sync. > Since device_del => device_pm_remove firstly, later _get_sync wouldn't really > wake up the device. > > I git log -p to find the patch which moves the calling to device_pm_remove ahead. > It's below patch: > > commit 775b64d2b6ca37697de925f70799c710aab5849a > Author: Rafael J. Wysocki <rjw@xxxxxxx> > Date: Sat Jan 12 20:40:46 2008 +0100 > > PM: Acquire device locks on suspend > > This patch reorganizes the way suspend and resume notifications are > sent to drivers. The major changes are that now the PM core acquires > every device semaphore before calling the methods, and calls to > device_add() during suspends will fail, while calls to device_del() > during suspends will block. > > It also provides a way to safely remove a suspended device with the > help of the PM core, by using the device_pm_schedule_removal() callback > introduced specifically for this purpose, and updates two drivers (msr > and cpuid) that need to use it. > > > As device_pm_schedule_removal is deleted by another patch, we need also revert > other parts of the patch, i.e. move the calling of device_pm_remove after > the calling to bus_remove_device. > > > > > Signed-off-by: LongX Zhang <longx.zhang@xxxxxxxxx> Can you please resend the patch? I lost the track of it unfortunately. Thanks, Rafael > > --- > > drivers/base/core.c | 2 +- > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > diff --git a/drivers/base/core.c b/drivers/base/core.c > > index 5e6e00b..81ea7f2 100644 > > --- a/drivers/base/core.c > > +++ b/drivers/base/core.c > > @@ -1169,7 +1169,6 @@ void device_del(struct device *dev) > > if (dev->bus) > > blocking_notifier_call_chain(&dev->bus->p->bus_notifier, > > BUS_NOTIFY_DEL_DEVICE, dev); > > - device_pm_remove(dev); > > dpm_sysfs_remove(dev); > > if (parent) > > klist_del(&dev->p->knode_parent); > > @@ -1194,6 +1193,7 @@ void device_del(struct device *dev) > > device_remove_file(dev, &uevent_attr); > > device_remove_attrs(dev); > > bus_remove_device(dev); > > + device_pm_remove(dev); > > driver_deferred_probe_del(dev); > > > > /* > > > -- I speak only for myself. Rafael J. Wysocki, Intel Open Source Technology Center.
