• Lorenzo Pieralisi's avatar
    ACPI / drivers: replace acpi_probe_lock spinlock with mutex · 5331d9ca
    Lorenzo Pieralisi authored
    Commit e647b532 ("ACPI: Add early device probing infrastructure")
    introduced code that allows inserting driver specific
    struct acpi_probe_entry probe entries into ACPI linker sections
    (one per-subsystem, eg irqchip, clocksource) that are then walked
    to retrieve the data and function hooks required to probe the
    respective kernel components.
    
    Probing for all entries in a section is triggered through
    the __acpi_probe_device_table() function, that in turn, according
    to the table ID a given probe entry reports parses the table
    with the function retrieved from the respective section structures
    (ie struct acpi_probe_entry). Owing to the current ACPI table
    parsing implementation, the __acpi_probe_device_table() function
    has to share global variables with the acpi_match_madt() function, so
    in order to guarantee mutual exclusion locking is required
    between the two functions.
    
    Current kernel code implements the locking through the acpi_probe_lock
    spinlock; this has the side effect of requiring all code called
    within the lock (ie struct acpi_probe_entry.probe_{table/subtbl} hooks)
    not to sleep.
    
    However, kernel subsystems that make use of the early probing
    infrastructure are relying on kernel APIs that may sleep (eg
    irq_domain_alloc_fwnode(), among others) in the function calls
    pointed at by struct acpi_probe_entry.{probe_table/subtbl} entries
    (eg gic_v2_acpi_init()), which is a bug.
    
    Since __acpi_probe_device_table() is called from context
    that is allowed to sleep the acpi_probe_lock spinlock can be replaced
    with a mutex; this fixes the issue whilst still guaranteeing
    mutual exclusion.
    Signed-off-by: default avatarLorenzo Pieralisi <lorenzo.pieralisi@arm.com>
    Fixes: e647b532 (ACPI: Add early device probing infrastructure)
    Cc: 4.4+ <stable@vger.kernel.org> # 4.4+
    Signed-off-by: default avatarRafael J. Wysocki <rafael.j.wysocki@intel.com>
    5331d9ca
scan.c 53 KB