ACPI / power: Avoid maybe-uninitialized warning

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 <arnd@arndb.de>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Signed-off-by: Jiri Slaby <jslaby@suse.cz>

diff --git a/drivers/acpi/power.c b/drivers/acpi/power.c
index c2ad391d8041ecb6a354e2df07b9d813d817a744..4b35a115749cd9252d35ac3f8612d5f69afad16c 100644 (file)
--- a/drivers/acpi/power.c
+++ b/drivers/acpi/power.c
@@ -204,6 +204,7 @@ static int acpi_power_get_list_state(struct list_head *list, int *state)
                return -EINVAL;
 
        /* The state of the list is 'on' IFF all resources are 'on'. */
+       cur_state = 0;
        list_for_each_entry(entry, list, node) {
                struct acpi_power_resource *resource = entry->resource;
                acpi_handle handle = resource->device.handle;