kernel/git/stable/linux.git/drivers/acpi/power.c, branch linux-3.2.y

ACPI / power: Avoid maybe-uninitialized warning

2017-07-18T17:38:43+00:00

commit fe8c470ab87d90e4b5115902dd94eced7e3305c3 upstream. gcc -O2 cannot always prove that the loop in acpi_power_get_inferred_state() is enterered at least once, so it assumes that cur_state might not get initialized: drivers/acpi/power.c: In function 'acpi_power_get_inferred_state': drivers/acpi/power.c:222:9: error: 'cur_state' may be used uninitialized in this function [-Werror=maybe-uninitialized] This sets the variable to zero at the start of the loop, to ensure that there is well-defined behavior even for an empty list. This gets rid of the warning. The warning first showed up when the -Os flag got removed in a bug fix patch in linux-4.11-rc5. I would suggest merging this addon patch on top of that bug fix to avoid introducing a new warning in the stable kernels. Fixes: 61b79e16c68d (ACPI: Fix incompatibility with mcount-based function graph tracing) Signed-off-by: Arnd Bergmann Signed-off-by: Rafael J. Wysocki [bwh: Backported to 3.2: adjust context] Signed-off-by: Ben Hutchings

ACPI / PM: Check status of power resources under mutexes

2011-01-12T10:05:39+00:00

It certainly is not a good idea to execute _ON or _OFF and _STA for the same power resource at the same time which may happen in some circumstances in theory. To prevent that from happening, read the power state of each power resource under its mutex, as that will prevent the state from being changed at the same time. Signed-off-by: Rafael J. Wysocki Signed-off-by: Len Brown

ACPI / PM: Rename acpi_power_off_device()

2011-01-12T10:05:23+00:00

Rename acpi_power_off_device() to acpi_power_off() in analogy with acpi_power_on(). Signed-off-by: Rafael J. Wysocki Signed-off-by: Len Brown

ACPI / PM: Drop acpi_power_nocheck

2011-01-12T09:48:45+00:00

Since acpi_bus_set_power() should not use __acpi_bus_get_power() to update the device's device->power.state field before changing its power state (this may cause device->power.state to be inconsistent with the device power resources' reference counters), remove this call from it. In consequence, the acpi_power_nocheck variable is not necessary any more, so it can be dropped along with the DMI table used for setting that variable for HP Pavilion 05. Signed-off-by: Rafael J. Wysocki Signed-off-by: Len Brown

ACPI / PM: Introduce function for refcounting device power resources

2011-01-12T09:48:44+00:00

Introduce function acpi_power_on_resources() that reference counts and possibly turns on ACPI power resources for a given device and a given power state of it. This function will be used for reference counting device power resources during initialization. Signed-off-by: Rafael J. Wysocki Signed-off-by: Len Brown

ACPI / PM: Add functions for manipulating lists of power resources

2011-01-12T09:48:43+00:00

ACPI device power resources should be reference counted during device initialization, so that their reference counters are always up to date. It is convenient to do that with the help of a function that will reference count and possibly turn on power resources in a given list, so introduce that function, acpi_power_on_list(). For symmetry, introduce acpi_power_off_list() for performing the reverse operation and use the both of them to simplify acpi_power_transition(). Signed-off-by: Rafael J. Wysocki Signed-off-by: Len Brown

ACPI / PM: Prevent acpi_power_get_inferred_state() from making changes

2011-01-12T09:48:43+00:00

acpi_power_get_inferred_state() should not update device->power.state behind the back of its caller, so make it return the state via a pointer instead. Signed-off-by: Rafael J. Wysocki Signed-off-by: Len Brown

ACPI / PM: Do not refcount power resources that can't be turned on

2010-12-01T21:53:39+00:00

If turning on a power resource fails, do not reference count it, since it cannot be in use in that case. Signed-off-by: Rafael J. Wysocki Signed-off-by: Len Brown

ACPI / PM: Check device state before refcounting power resources

2010-12-01T21:53:16+00:00

Commit 3e384ee6c687cb397581ee8f9440fc8220cfac80 (ACPI / PM: Fix reference counting of power resources) introduced a regression by causing fan power resources to be turned on and reference counted unnecessarily during resume, so on some boxes fans are always on after resume. Fix the problem by checking if the current device state is different from the new state before reference counting and turning on power resources in acpi_power_transition(). Addresses https://bugzilla.kernel.org/show_bug.cgi?id=22932 . Signed-off-by: Rafael J. Wysocki Reported-and-tested-by: Maciej Rutecki Signed-off-by: Len Brown

ACPI / PM: Fix reference counting of power resources

2010-10-23T05:56:14+00:00

The reference counting of ACPI power resources is currently broken for a few reasons. First, instead of using a simple reference counter per power resource it uses a list of objects representing refereces to the given power resource from devices. This leads to the second breakage, because it prevents power resources from being referenced more than once by one device, which is necessary if the device is configured to signal wakeup. Namely, when putting the device into a low power state we first call acpi_enable_wakeup_device_power() that should reference count power resources needed for signaling wakeup and then we call acpi_power_transition() to power off the device. The latter call drops references to the device's power resources, possibly including the ones added by acpi_enable_wakeup_device_power(), so the device can't signal wakeup as a result. Apart from this, the locking in acpi_power_on() and acpi_power_off_device() doesn't prevent all possible races from happening, which may be problematic for runtime PM and asynchronous suspend and resume. Fix the problem by using a counter for power resources reference counting and putting the evaluation of ACPI _ON and _OFF methods under the power resource mutex. Reported-by: Matthew Garrett Signed-off-by: Rafael J. Wysocki Signed-off-by: Len Brown