• Lv Zheng's avatar
    ACPICA: Namespace: Fix dynamic table loading issues · 74f51b80
    Lv Zheng authored
    ACPICA commit 767ee53354e0c4b7e8e7c57c6dd7bf569f0d52bb
    
    There are issues related to the namespace/interpreter locks, which causes
    several ACPI functionalities not specification compliant. The lock issues
    were detectec when we were trying to fix the functionalities (please see
    Link # [1] for the details).
    
    What's the lock issues? Let's first look into the namespace/interpreter
    lock usages inside of the object evaluation and the table loading which are
    the key AML interpretion code paths:
    Table loading:
    acpi_ns_load_table
    	L(Namespace)
    	acpi_ns_parse_table
    		acpi_ns_one_complete_parse(LOAD_PASS1/LOAD_PASS2)
    			acpi_ds_load1_begion_op
    			acpi_ds_load1_end_op
    			acpi_ds_load2_begion_op
    			acpi_ds_load2_end_op
    	U(Namespace)
    Object evaluation:
    acpi_ns_evaluate
    	L(Interpreter)
    	acpi_ps_execute_method
    		acpi_ds_exec_begin_op
    		acpi_ds_exec_end_op
    			U(Interpreter)
    			acpi_ns_load_table
    				L(Namespace)
    				U(Namespace)
    			acpi_ev_initialize_region
    				L(Namespace)
    				U(Namespace)
    			address_space.Setup
    			address_space.Handler
    			acpi_os_wait_semaphore
    			acpi_os_acquire_mutex
    			acpi_os_sleep
    			L(Interpreter)
    	U(Interpreter)
    	L(Interpreter)
    	acpi_ex_resolve_node_to_value
    	U(Interpreter)
    	acpi_ns_check_return_value
    Where:
      1. L(Interpreter) means acquire(MTX_INTERPRETER);
      2. U(Interpreter) means release(MTX_INTERPRETER);
      3. L(Namespace) means acquire(MTX_NAMESPACE);
      4. U(Namespace) means release(MTX_NAMESPACE);
    
    We can see that acpi_ns_exec_module_code() (which invokes acpi_ns_evaluate) is
    implemented in a deferred way just in order to avoid to reacquire the
    namespace lock. This is in fact the root cause of many other ACPICA issues:
    1. We now know for sure that the module code should be executed right in
       place by the Windows AML interpreter. So in the current design, if
       the region initializations/accesses or the table loadings (where the
       namespace surely should be locked again) happening during the table
       loading period, dead lock could happen because ACPICA never unlocks the
       namespace during the AML interpretion.
    2. ACPICA interpreter just ensures that all static namespace nodes (named
       objects created during the acpi_load_tables()) are created
       (acpi_ns_lookup()) with the correct lock held, but doesn't ensure that
       the named objects created by the control method are created with the
       same correct lock held. It requires the control methods to be executed
       in a serial way after "loading a table", that's why ACPICA requires
       method auto serialization.
    
    This patch fixes these software design issues by extending interpreter
    enter/exit APIs to hold both interpreter/namespace locks to ensure the lock
    order correctness, so that we can get these code paths:
    Table loading:
    acpi_ns_load_table
    	E(Interpreter)
    		acpi_ns_parse_table
    			acpi_ns_one_complete_parse
    			acpi_ns_execute_table
    				X(Interpreter)
    				acpi_ns_load_table
    				acpi_ev_initialize_region
    				address_space.Setup
    				address_space.Handler
    				acpi_os_wait_semaphore
    				acpi_os_acquire_mutex
    				acpi_os_sleep
    				E(Interpreter)
    	X(Interpreter)
    Object evaluation:
    acpi_ns_evaluate
    	E(Interpreter)
    	acpi_ps_execute_method
    		X(Interpreter)
    		acpi_ns_load_table
    		acpi_ev_initialize_region
    		address_space.Setup
    		address_space.Handler
    		acpi_os_wait_semaphore
    		acpi_os_acquire_mutex
    		acpi_os_sleep
    		E(Interpreter)
    	X(Interpreter)
    Where:
      1. E(Interpreter) means acquire(MTX_INTERPRETER, MTX_NAMESPACE);
      2. X(Interpreter) means release(MTX_NAMESPACE, MTX_INTERPRETER);
    
    After this change, we can see:
    1. All namespace nodes creations are locked by the namespace lock.
    2. All namespace nodes referencing are locked with the same lock.
    3. But we also can notice a defact that, all namespace nodes deletions
       could be affected by this change. As a consequence,
       acpi_ns_delete_namespace_subtree() may delete a static namespace node that
       is still referenced by the interpreter (for example, the parser scopes).
    Currently, we needn't worry about the last defact because in ACPICA, table
    unloading is not fully functioning, its design strictly relies on the fact
    that when the namespace deletion happens, either the AML table or the OSPMs
    should have been notified and thus either the AML table or the OSPMs
    shouldn't reference deletion-related namespace nodes during the namespace
    deletion. And this change still works with the above restrictions applied.
    While making this a-step-forward helps us to correct the wrong grammar to
    pull many things back to the correct rail. And pulling things back to the
    correct rail in return makes it possible for us to support fully
    functioning table unloading after doing many cleanups.
    
    While this patch is generated, all namespace locks are examined to ensure
    that they can meet either of the following pattens:
    1. L(Namespace)
       U(Namespace)
    2. E(Interpreter)
       X(Interpreter)
    3. E(Interpreter)
       X(Interpreter)
       L(Namespace)
       U(Namespace)
       E(Interpreter)
       X(Interpreter)
    We ensure this by adding X(Interpreter)/E(Interpreter) or removing
    U(Namespace)/L(Namespace) for those currently are executed in the following
    order:
       E(Interpreter)
       L(Namespace)
       U(Namespace)
       X(Interpreter)
    And adding E(Interpreter)/X(Interpreter) for those currently are executed
    in the following order:
       X(Interpreter)
       E(Interpreter)
    
    Originally, the interpreter lock is held for the execution AML opcodes, the
    namespace lock is held for the named object creation AML opcodes. Since
    they are actually same in MS interpreter (can all be executed during the
    table loading), we can combine the 2 locks and tune the locking code better
    in this way. Lv Zheng.
    
    Link: https://bugzilla.kernel.org/show_bug.cgi?id=153541 # [1]
    Link: https://bugzilla.kernel.org/show_bug.cgi?id=121701 # [1]
    Link: https://bugs.acpica.org/show_bug.cgi?id=1323
    Link: https://github.com/acpica/acpica/commit/767ee533Reported-and-tested-by: default avatarMika Westerberg <mika.westerberg@linux.intel.com>
    Reported-and-tested-by: default avatarGreg White <gwhite@kupulau.com>
    Reported-and-tested-by: default avatarDutch Guy <lucht_piloot@gmx.net>
    Signed-off-by: default avatarLv Zheng <lv.zheng@intel.com>
    Signed-off-by: default avatarBob Moore <robert.moore@intel.com>
    Signed-off-by: default avatarRafael J. Wysocki <rafael.j.wysocki@intel.com>
    74f51b80
exconfig.c 17.9 KB