| Message ID | 1311371188-28879-1-git-send-email-khilman@ti.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Friday, July 22, 2011, Kevin Hilman wrote: > Currently the use of pm_runtime_put_sync() is not safe from > interrupts-disabled context because rpm_idle() will release the > spinlock and enable interrupts for the idle callbacks. This enables > interrupts during a time where interrupts were expected to be > disabled, and can have strange side effects on drivers that expected > interrupts to be disabled. > > This is not a bug since the documentation clearly states that only > _put_sync_suspend() is safe in IRQ-safe mode. > > However, pm_runtime_put_sync() could be made safe when in IRQ-safe > mode by releasing the spinlock but not re-enabling interrupts, which > is what this patch aims to do. > > Problem was found when using some buggy drivers that set > pm_runtime_irq_safe() and used _put_sync() in interrupts-disabled > context. > > The offending drivers have been fixed to use _put_sync_suspend(), > But this patch is an RFC to see if it might make sense to allow > using _put_sync() from interrupts-disabled context. OK, I'm going to take this for 3.2. Thanks, Rafael > Reported-by: Colin Cross <ccross@google.com> > Tested-by: Nishanth Menon <nm@ti.com> > Signed-off-by: Kevin Hilman <khilman@ti.com> > --- > v2: update documentation also > > Documentation/power/runtime_pm.txt | 10 +++++----- > drivers/base/power/runtime.c | 10 ++++++++-- > 2 files changed, 13 insertions(+), 7 deletions(-) > > diff --git a/Documentation/power/runtime_pm.txt b/Documentation/power/runtime_pm.txt > index 14dd3c6..4ce5450 100644 > --- a/Documentation/power/runtime_pm.txt > +++ b/Documentation/power/runtime_pm.txt > @@ -54,11 +54,10 @@ referred to as subsystem-level callbacks in what follows. > By default, the callbacks are always invoked in process context with interrupts > enabled. However, subsystems can use the pm_runtime_irq_safe() helper function > to tell the PM core that a device's ->runtime_suspend() and ->runtime_resume() > -callbacks should be invoked in atomic context with interrupts disabled > -(->runtime_idle() is still invoked the default way). This implies that these > -callback routines must not block or sleep, but it also means that the > -synchronous helper functions listed at the end of Section 4 can be used within > -an interrupt handler or in an atomic context. > +callbacks should be invoked in atomic context with interrupts disabled. > +This implies that these callback routines must not block or sleep, but it also > +means that the synchronous helper functions listed at the end of Section 4 can > +be used within an interrupt handler or in an atomic context. > > The subsystem-level suspend callback is _entirely_ _responsible_ for handling > the suspend of the device as appropriate, which may, but need not include > @@ -483,6 +482,7 @@ pm_runtime_suspend() > pm_runtime_autosuspend() > pm_runtime_resume() > pm_runtime_get_sync() > +pm_runtime_put_sync() > pm_runtime_put_sync_suspend() > > 5. Runtime PM Initialization, Device Probing and Removal > diff --git a/drivers/base/power/runtime.c b/drivers/base/power/runtime.c > index 8dc247c..acb3f83 100644 > --- a/drivers/base/power/runtime.c > +++ b/drivers/base/power/runtime.c > @@ -226,11 +226,17 @@ static int rpm_idle(struct device *dev, int rpmflags) > callback = NULL; > > if (callback) { > - spin_unlock_irq(&dev->power.lock); > + if (dev->power.irq_safe) > + spin_unlock(&dev->power.lock); > + else > + spin_unlock_irq(&dev->power.lock); > > callback(dev); > > - spin_lock_irq(&dev->power.lock); > + if (dev->power.irq_safe) > + spin_lock(&dev->power.lock); > + else > + spin_lock_irq(&dev->power.lock); > } > > dev->power.idle_notification = false; >
"Rafael J. Wysocki" <rjw@sisk.pl> writes: > On Friday, July 22, 2011, Kevin Hilman wrote: >> Currently the use of pm_runtime_put_sync() is not safe from >> interrupts-disabled context because rpm_idle() will release the >> spinlock and enable interrupts for the idle callbacks. This enables >> interrupts during a time where interrupts were expected to be >> disabled, and can have strange side effects on drivers that expected >> interrupts to be disabled. >> >> This is not a bug since the documentation clearly states that only >> _put_sync_suspend() is safe in IRQ-safe mode. >> >> However, pm_runtime_put_sync() could be made safe when in IRQ-safe >> mode by releasing the spinlock but not re-enabling interrupts, which >> is what this patch aims to do. >> >> Problem was found when using some buggy drivers that set >> pm_runtime_irq_safe() and used _put_sync() in interrupts-disabled >> context. >> >> The offending drivers have been fixed to use _put_sync_suspend(), >> But this patch is an RFC to see if it might make sense to allow >> using _put_sync() from interrupts-disabled context. > > OK, I'm going to take this for 3.2. > OK, great. Thanks. Might want to just drop the last paragraph from the changelog since it doesn't really belong in the permanant history. Kevin
On Wednesday, July 27, 2011, Kevin Hilman wrote: > "Rafael J. Wysocki" <rjw@sisk.pl> writes: > > > On Friday, July 22, 2011, Kevin Hilman wrote: > >> Currently the use of pm_runtime_put_sync() is not safe from > >> interrupts-disabled context because rpm_idle() will release the > >> spinlock and enable interrupts for the idle callbacks. This enables > >> interrupts during a time where interrupts were expected to be > >> disabled, and can have strange side effects on drivers that expected > >> interrupts to be disabled. > >> > >> This is not a bug since the documentation clearly states that only > >> _put_sync_suspend() is safe in IRQ-safe mode. > >> > >> However, pm_runtime_put_sync() could be made safe when in IRQ-safe > >> mode by releasing the spinlock but not re-enabling interrupts, which > >> is what this patch aims to do. > >> > >> Problem was found when using some buggy drivers that set > >> pm_runtime_irq_safe() and used _put_sync() in interrupts-disabled > >> context. > >> > >> The offending drivers have been fixed to use _put_sync_suspend(), > >> But this patch is an RFC to see if it might make sense to allow > >> using _put_sync() from interrupts-disabled context. > > > > OK, I'm going to take this for 3.2. > > > > OK, great. Thanks. > > Might want to just drop the last paragraph from the changelog since it > doesn't really belong in the permanant history. OK Thanks, Rafael
"Rafael J. Wysocki" <rjw@sisk.pl> writes: > On Friday, July 22, 2011, Kevin Hilman wrote: >> Currently the use of pm_runtime_put_sync() is not safe from >> interrupts-disabled context because rpm_idle() will release the >> spinlock and enable interrupts for the idle callbacks. This enables >> interrupts during a time where interrupts were expected to be >> disabled, and can have strange side effects on drivers that expected >> interrupts to be disabled. >> >> This is not a bug since the documentation clearly states that only >> _put_sync_suspend() is safe in IRQ-safe mode. >> >> However, pm_runtime_put_sync() could be made safe when in IRQ-safe >> mode by releasing the spinlock but not re-enabling interrupts, which >> is what this patch aims to do. >> >> Problem was found when using some buggy drivers that set >> pm_runtime_irq_safe() and used _put_sync() in interrupts-disabled >> context. >> >> The offending drivers have been fixed to use _put_sync_suspend(), >> But this patch is an RFC to see if it might make sense to allow >> using _put_sync() from interrupts-disabled context. > > OK, I'm going to take this for 3.2. Rafael, Since you're planning to merge this, maybe we should consider merging this as a fix for v3.1, and possibly even for v3.0 stable. That way, any current drivers using irq_safe and the normal _put_sync() will not have this problem. Kevin
On Friday, August 05, 2011, Kevin Hilman wrote: > "Rafael J. Wysocki" <rjw@sisk.pl> writes: > > > On Friday, July 22, 2011, Kevin Hilman wrote: > >> Currently the use of pm_runtime_put_sync() is not safe from > >> interrupts-disabled context because rpm_idle() will release the > >> spinlock and enable interrupts for the idle callbacks. This enables > >> interrupts during a time where interrupts were expected to be > >> disabled, and can have strange side effects on drivers that expected > >> interrupts to be disabled. > >> > >> This is not a bug since the documentation clearly states that only > >> _put_sync_suspend() is safe in IRQ-safe mode. > >> > >> However, pm_runtime_put_sync() could be made safe when in IRQ-safe > >> mode by releasing the spinlock but not re-enabling interrupts, which > >> is what this patch aims to do. > >> > >> Problem was found when using some buggy drivers that set > >> pm_runtime_irq_safe() and used _put_sync() in interrupts-disabled > >> context. > >> > >> The offending drivers have been fixed to use _put_sync_suspend(), > >> But this patch is an RFC to see if it might make sense to allow > >> using _put_sync() from interrupts-disabled context. > > > > OK, I'm going to take this for 3.2. > > Rafael, > > Since you're planning to merge this, maybe we should consider merging > this as a fix for v3.1, and possibly even for v3.0 stable. That way, > any current drivers using irq_safe and the normal _put_sync() will not > have this problem. I think I can push it for 3.1, but I don't think it's stable material. Thanks, Rafael
"Rafael J. Wysocki" <rjw@sisk.pl> writes: > On Friday, August 05, 2011, Kevin Hilman wrote: >> "Rafael J. Wysocki" <rjw@sisk.pl> writes: >> >> > On Friday, July 22, 2011, Kevin Hilman wrote: >> >> Currently the use of pm_runtime_put_sync() is not safe from >> >> interrupts-disabled context because rpm_idle() will release the >> >> spinlock and enable interrupts for the idle callbacks. This enables >> >> interrupts during a time where interrupts were expected to be >> >> disabled, and can have strange side effects on drivers that expected >> >> interrupts to be disabled. >> >> >> >> This is not a bug since the documentation clearly states that only >> >> _put_sync_suspend() is safe in IRQ-safe mode. >> >> >> >> However, pm_runtime_put_sync() could be made safe when in IRQ-safe >> >> mode by releasing the spinlock but not re-enabling interrupts, which >> >> is what this patch aims to do. >> >> >> >> Problem was found when using some buggy drivers that set >> >> pm_runtime_irq_safe() and used _put_sync() in interrupts-disabled >> >> context. >> >> >> >> The offending drivers have been fixed to use _put_sync_suspend(), >> >> But this patch is an RFC to see if it might make sense to allow >> >> using _put_sync() from interrupts-disabled context. >> > >> > OK, I'm going to take this for 3.2. >> >> Rafael, >> >> Since you're planning to merge this, maybe we should consider merging >> this as a fix for v3.1, and possibly even for v3.0 stable. That way, >> any current drivers using irq_safe and the normal _put_sync() will not >> have this problem. > > I think I can push it for 3.1, but I don't think it's stable material. > OK, fair enough. Kevin
diff --git a/Documentation/power/runtime_pm.txt b/Documentation/power/runtime_pm.txt index 14dd3c6..4ce5450 100644 --- a/Documentation/power/runtime_pm.txt +++ b/Documentation/power/runtime_pm.txt @@ -54,11 +54,10 @@ referred to as subsystem-level callbacks in what follows. By default, the callbacks are always invoked in process context with interrupts enabled. However, subsystems can use the pm_runtime_irq_safe() helper function to tell the PM core that a device's ->runtime_suspend() and ->runtime_resume() -callbacks should be invoked in atomic context with interrupts disabled -(->runtime_idle() is still invoked the default way). This implies that these -callback routines must not block or sleep, but it also means that the -synchronous helper functions listed at the end of Section 4 can be used within -an interrupt handler or in an atomic context. +callbacks should be invoked in atomic context with interrupts disabled. +This implies that these callback routines must not block or sleep, but it also +means that the synchronous helper functions listed at the end of Section 4 can +be used within an interrupt handler or in an atomic context. The subsystem-level suspend callback is _entirely_ _responsible_ for handling the suspend of the device as appropriate, which may, but need not include @@ -483,6 +482,7 @@ pm_runtime_suspend() pm_runtime_autosuspend() pm_runtime_resume() pm_runtime_get_sync() +pm_runtime_put_sync() pm_runtime_put_sync_suspend() 5. Runtime PM Initialization, Device Probing and Removal diff --git a/drivers/base/power/runtime.c b/drivers/base/power/runtime.c index 8dc247c..acb3f83 100644 --- a/drivers/base/power/runtime.c +++ b/drivers/base/power/runtime.c @@ -226,11 +226,17 @@ static int rpm_idle(struct device *dev, int rpmflags) callback = NULL; if (callback) { - spin_unlock_irq(&dev->power.lock); + if (dev->power.irq_safe) + spin_unlock(&dev->power.lock); + else + spin_unlock_irq(&dev->power.lock); callback(dev); - spin_lock_irq(&dev->power.lock); + if (dev->power.irq_safe) + spin_lock(&dev->power.lock); + else + spin_lock_irq(&dev->power.lock); } dev->power.idle_notification = false;