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ACPICA: Fix AcpiWalkNamespace race condition with table unload

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Added a reader/writer locking mechanism to allow multiple
concurrent namespace walks (readers), but a dynamic table unload
will have exclusive access to the namespace. This fixes a problem
where a table unload could delete the portion of the namespace that
is currently being examined by a walk.  Adds a new file, utlock.c
that implements the reader/writer lock mechanism. ACPICA BZ 749.

http://www.acpica.org/bugzilla/show_bug.cgi?id=749

Signed-off-by: Bob Moore <robert.moore@intel.com>
Signed-off-by: Lin Ming <ming.m.lin@intel.com>
Signed-off-by: Len Brown <len.brown@intel.com>
This commit is contained in:
Bob Moore
2009-03-09 16:31:04 +08:00
committed by Len Brown
parent aab61b676a
commit 8a335a2331
11 changed files with 304 additions and 34 deletions
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33
drivers/acpi/acpica/nsxfeval.c
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@@ -475,21 +475,40 @@ acpi_walk_namespace(acpi_object_type type,
}
/*
* Lock the namespace around the walk.
* The namespace will be unlocked/locked around each call
* to the user function - since this function
* must be allowed to make Acpi calls itself.
* Need to acquire the namespace reader lock to prevent interference
* with any concurrent table unloads (which causes the deletion of
* namespace objects). We cannot allow the deletion of a namespace node
* while the user function is using it. The exception to this are the
* nodes created and deleted during control method execution -- these
* nodes are marked as temporary nodes and are ignored by the namespace
* walk. Thus, control methods can be executed while holding the
* namespace deletion lock (and the user function can execute control
* methods.)
*/
status = acpi_ut_acquire_read_lock(&acpi_gbl_namespace_rw_lock);
if (ACPI_FAILURE(status)) {
return status;
}
/*
* Lock the namespace around the walk. The namespace will be
* unlocked/locked around each call to the user function - since the user
* function must be allowed to make ACPICA calls itself (for example, it
* will typically execute control methods during device enumeration.)
*/
status = acpi_ut_acquire_mutex(ACPI_MTX_NAMESPACE);
if (ACPI_FAILURE(status)) {
return_ACPI_STATUS(status);
goto unlock_and_exit;
}
status = acpi_ns_walk_namespace(type, start_object, max_depth,
ACPI_NS_WALK_UNLOCK,
user_function, context, return_value);
ACPI_NS_WALK_UNLOCK, user_function,
context, return_value);
(void)acpi_ut_release_mutex(ACPI_MTX_NAMESPACE);
unlock_and_exit:
(void)acpi_ut_release_read_lock(&acpi_gbl_namespace_rw_lock);
return_ACPI_STATUS(status);
}