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    Subject[PATCH v2] ACPI: fix acpi_power_off lockdep splat
    Date
    Implement acpi_os_create_lock() as a C-preprocessor macro to suppress
    lockdep false positive.

    When lockdep is enabled the spin_lock_init macro stringifies it's
    argument and uses that as a name for the lock in the debugging.

    By executing spin_lock_init in a macro the key changes from "lock" for
    all locks to the actual argument of acpi_os_create_lock()
    ("&acpi_gbl_global_lock_pending_lock", "&acpi_gbl_gpe_lock" or
    "&acpi_gbl_hardware_lock" for now).

    This fixes:
    https://bugzilla.kernel.org/show_bug.cgi?id=38152

    ChangeLog (v1 -> v2):
    - avoid to call spin_lock_init multiple times on the same lock
    - rewrite patch description (thanks to Florian for providing a better
    description of the patch)

    Reported-by: Borislav Petkov <bp@alien8.de>
    CC: Florian Mickler <florian@mickler.org>
    Signed-off-by: Andrea Righi <andrea@betterlinux.com>
    ---
    drivers/acpi/osl.c | 3 +--
    include/acpi/acpiosxf.h | 12 +++++++++++-
    2 files changed, 12 insertions(+), 3 deletions(-)

    diff --git a/drivers/acpi/osl.c b/drivers/acpi/osl.c
    index 52ca964..4c985d3 100644
    --- a/drivers/acpi/osl.c
    +++ b/drivers/acpi/osl.c
    @@ -1336,14 +1336,13 @@ EXPORT_SYMBOL(acpi_resources_are_enforced);
    * Create and initialize a spinlock.
    */
    acpi_status
    -acpi_os_create_lock(acpi_spinlock *out_handle)
    +__acpi_os_create_lock(acpi_spinlock *out_handle)
    {
    spinlock_t *lock;

    lock = ACPI_ALLOCATE(sizeof(spinlock_t));
    if (!lock)
    return AE_NO_MEMORY;
    - spin_lock_init(lock);
    *out_handle = lock;

    return AE_OK;
    diff --git a/include/acpi/acpiosxf.h b/include/acpi/acpiosxf.h
    index a756bc8..4a0385d 100644
    --- a/include/acpi/acpiosxf.h
    +++ b/include/acpi/acpiosxf.h
    @@ -99,7 +99,17 @@ acpi_os_table_override(struct acpi_table_header *existing_table,
    * Spinlock primitives
    */
    acpi_status
    -acpi_os_create_lock(acpi_spinlock *out_handle);
    +__acpi_os_create_lock(acpi_spinlock *out_handle);
    +
    +#define acpi_os_create_lock(__handle) \
    +({ \
    + acpi_status ret; \
    + \
    + ret = __acpi_os_create_lock(__handle); \
    + if (ret == AE_OK) \
    + spin_lock_init(*(__handle)); \
    + ret; \
    +})

    void acpi_os_delete_lock(acpi_spinlock handle);

    --
    1.7.4.1


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