tree 0eaaaeee0a25b9bb2c86260f6a7ab0fb3fab9099
parent 2f38b1b16d9280689e5cfa47a4c50956bf437f0d
author Lv Zheng <lv.zheng@intel.com> 1467697992 +0800
committer Rafael J. Wysocki <rafael.j.wysocki@intel.com> 1467751724 +0200

ACPICA: Namespace: Fix namespace/interpreter lock ordering

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: 2f38b1b16d9280689e5cfa47a4c50956bf437f0d
  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: 2f38b1b16d92 (ACPICA: Namespace: Fix a regression that MLC support triggers dead lock in dynamic table loading)
Signed-off-by: Lv Zheng <lv.zheng@intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>