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.
Reported-by: Colin Cross <ccross@xxxxxxxxxx>
Tested-by: Nishanth Menon <nm@xxxxxx>
Signed-off-by: Kevin Hilman <khilman@xxxxxx>
---
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;
--
1.7.6
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