PM / Runtime: Allow _put_sync() from interrupts-disabled context

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.

Reported-by: Colin Cross <ccross@google.com>
Tested-by: Nishanth Menon <nm@ti.com>
Signed-off-by: Kevin Hilman <khilman@ti.com>
Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>

1 files changed, 8 insertions, 2 deletions

diff --git a/drivers/base/power/runtime.c b/drivers/base/power/runtime.c
index 8dc247c974af..acb3f83b8079 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;