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SubjectRe: [PATCH] PCI / PM: Block races between runtime PM and system sleep
Date
On Thursday, June 23, 2011, Alan Stern wrote:
> On Thu, 23 Jun 2011, Rafael J. Wysocki wrote:
>
> > OK, so what about the appended patch (the last hunk is necessary to make the
> > SCSI error handling work when runtime PM is disabled, it should be a separate
> > patch)?
> >
> > Rafael
> >
> > ---
> > drivers/base/power/main.c | 27 ++++++++++++++++++++++-----
> > drivers/base/power/runtime.c | 10 ++++++----
> > 2 files changed, 28 insertions(+), 9 deletions(-)
> >
> > Index: linux-2.6/drivers/base/power/main.c
> > ===================================================================
> > --- linux-2.6.orig/drivers/base/power/main.c
> > +++ linux-2.6/drivers/base/power/main.c
> > @@ -505,6 +505,7 @@ static int legacy_resume(struct device *
> > static int device_resume(struct device *dev, pm_message_t state, bool async)
> > {
> > int error = 0;
> > + bool put = false;
> >
> > TRACE_DEVICE(dev);
> > TRACE_RESUME(0);
> > @@ -521,6 +522,9 @@ static int device_resume(struct device *
> > if (!dev->power.is_suspended)
> > goto Unlock;
> >
> > + pm_runtime_enable(dev);
> > + put = true;
> > +
> > if (dev->pwr_domain) {
> > pm_dev_dbg(dev, state, "power domain ");
> > error = pm_op(dev, &dev->pwr_domain->ops, state);
> > @@ -563,6 +567,10 @@ static int device_resume(struct device *
> > complete_all(&dev->power.completion);
> >
> > TRACE_RESUME(error);
> > +
> > + if (put)
> > + pm_runtime_put_sync(dev);
> > +
> > return error;
> > }
> >
> > @@ -843,16 +851,22 @@ static int __device_suspend(struct devic
> > int error = 0;
> >
> > dpm_wait_for_children(dev, async);
> > - device_lock(dev);
> >
> > if (async_error)
> > - goto Unlock;
> > + return 0;
> > +
> > + pm_runtime_get_noresume(dev);
> > + if (pm_runtime_barrier(dev) && device_may_wakeup(dev))
> > + pm_wakeup_event(dev, 0);
> >
> > if (pm_wakeup_pending()) {
> > + pm_runtime_put_sync(dev);
> > async_error = -EBUSY;
> > - goto Unlock;
> > + return 0;
> > }
> >
> > + device_lock(dev);
> > +
> > if (dev->pwr_domain) {
> > pm_dev_dbg(dev, state, "power domain ");
> > error = pm_op(dev, &dev->pwr_domain->ops, state);
> > @@ -890,12 +904,15 @@ static int __device_suspend(struct devic
> > End:
> > dev->power.is_suspended = !error;
> >
> > - Unlock:
> > device_unlock(dev);
> > complete_all(&dev->power.completion);
> >
> > - if (error)
> > + if (error) {
> > + pm_runtime_put_sync(dev);
> > async_error = error;
> > + } else if (dev->power.is_suspended) {
> > + __pm_runtime_disable(dev, false);
> > + }
> >
> > return error;
> > }
>
> Looks right.

Great! I'll prepare a final version with a changelog and documentation
update, then.

> > Index: linux-2.6/drivers/base/power/runtime.c
> > ===================================================================
> > --- linux-2.6.orig/drivers/base/power/runtime.c
> > +++ linux-2.6/drivers/base/power/runtime.c
> > @@ -455,12 +455,14 @@ static int rpm_resume(struct device *dev
> > dev_dbg(dev, "%s flags 0x%x\n", __func__, rpmflags);
> >
> > repeat:
> > - if (dev->power.runtime_error)
> > + if (dev->power.runtime_error) {
> > retval = -EINVAL;
> > - else if (dev->power.disable_depth > 0)
> > - retval = -EAGAIN;
> > - if (retval)
> > goto out;
> > + } else if (dev->power.disable_depth > 0) {
> > + if (!(rpmflags & RPM_GET_PUT))
> > + retval = -EAGAIN;
>
> Do you also want to check the current status? If it isn't RPM_ACTIVE
> then perhaps you should return an error.

That depends on whether or not we want RPM_ACTIVE to have any meaning for
devices whose power.disable_depth is nonzero. My opinion is that if
power.disable_depth is nonzero, the runtime PM status of the device
shouldn't matter (it may be changed on the fly in ways that need not
reflect the real status).

Thanks,
Rafael


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