• Lv Zheng's avatar
    ACPICA: Namespace: Fix namespace/interpreter lock ordering · 45209046
    Lv Zheng authored
    There is a lock order issue in acpi_load_tables(). The namespace lock
    is held before holding the interpreter lock.
    
    With ACPI_MUTEX_DEBUG enabled in the kernel, this is printed to the
    log during boot:
    
      [    0.885699] ACPI Error: Invalid acquire order: Thread 405884224 owns [ACPI_MTX_Namespace], wants [ACPI_MTX_Interpreter] (20160422/utmutex-263)
      [    0.885881] ACPI Error: Could not acquire AML Interpreter mutex (20160422/exutils-95)
      [    0.893846] ACPI Error: Mutex [0x0] is not acquired, cannot release (20160422/utmutex-326)
      [    0.894019] ACPI Error: Could not release AML Interpreter mutex (20160422/exutils-133)
    
    The issue has been introduced by the following commit:
    
      Commit: 2f38b1b1
      ACPICA Commit: bfe03ffcde8ed56a7eae38ea0b188aeb12f9c52e
      Subject: ACPICA: Namespace: Fix a regression that MLC support triggers
               dead lock in dynamic table loading
    
    Which fixed a deadlock issue for acpi_ns_load_table() in
    acpi_ex_add_table() but didn't take care of the lock order in
    acpi_ns_load_table() correctly.
    
    Originally (before the above commit), ACPICA used the
    namespace/interpreter locks in the following 2 key code
    paths:
    
     1. Table loading:
     acpi_ns_load_table
    	L(Namespace)
    		acpi_ns_parse_table
    			acpi_ns_one_complete_parse
    	U(Namespace)
     2. Object evaluation:
     acpi_ns_evaluate
    	L(Interpreter)
    	acpi_ps_execute_method
    		U(Interpreter)
    		acpi_ns_load_table
    			L(Namespace)
    			U(Namespace)
    		acpi_ev_initialize_region
    			L(Namespace)
    			U(Namespace)
    		address_space.setup
    			L(Namespace)
    			U(Namespace)
    		address_space.handler
    			L(Namespace)
    			U(Namespace)
    		acpi_os_wait_semaphore
    		acpi_os_acquire_mutex
    		acpi_os_sleep
    		L(Interpreter)
    	U(Interpreter)
    
    During runtime, while acpi_ns_evaluate is called, the lock order is
    always Interpreter -> Namespace.
    
    In turn, the problematic commit acquires the locks in the following
    order:
    
     3. Table loading:
     acpi_ns_load_table
    	L(Namespace)
    		acpi_ns_parse_table
    		L(Interpreter)
    			acpi_ns_one_complete_parse
    		U(Interpreter)
    	U(Namespace)
    
    To fix the lock order issue, move the interpreter lock to
    acpi_ns_load_table() to ensure the lock order correctness:
    
     4. Table loading:
     acpi_ns_load_table
    	L(Interpreter)
    	L(Namespace)
    		acpi_ns_parse_table
    			acpi_ns_one_complete_parse
    	U(Namespace)
    	U(Interpreter)
    
    However, this doesn't fix the current design issues related to the
    namespace lock. For example, we can notice that in acpi_ns_evaluate(),
    outside of acpi_ns_load_table(), the namespace objects may be created
    by the named object creation control methods. And the creation of
    the method-owned namespace objects are not locked by the namespace
    lock. This patch doesn't try to fix such kind of existing issues.
    
    Fixes: 2f38b1b1 (ACPICA: Namespace: Fix a regression that MLC support triggers dead lock in dynamic table loading)
    Signed-off-by: default avatarLv Zheng <lv.zheng@intel.com>
    Signed-off-by: default avatarRafael J. Wysocki <rafael.j.wysocki@intel.com>
    45209046
nsparse.c 6.59 KB