Fix AcpiWalkNamespace race condition with table unload.

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.

generate/linux/Makefile.acpiexec

@@ -120,6 +120,7 @@ SRCS=	aeexec.c aemain.c \
 	../../utilities/uteval.c \
 	../../utilities/utglobal.c \
 	../../utilities/utinit.c \
+	../../utilities/utlock.c \
 	../../utilities/utmath.c \
 	../../utilities/utmisc.c \
 	../../utilities/utmutex.c \

generate/linux/Makefile.iasl

@@ -14,6 +14,7 @@ SRCS=	aslcompilerparse.c aslcompilerlex.c aslanalyze.c aslcodegen.c \
 	../utilities/utdelete.c \
 	../utilities/utglobal.c \
 	../utilities/utinit.c \
+	../utilities/utlock.c \
 	../utilities/utobject.c \
 	../utilities/utmisc.c \
 	../utilities/utmath.c \

source/components/dispatcher/dsinit.c

@@ -272,12 +272,23 @@ AcpiDsInitializeObjects (
 
     /* Walk entire namespace from the supplied root */
 
-    Status = AcpiWalkNamespace (ACPI_TYPE_ANY, StartNode, ACPI_UINT32_MAX,
-                    AcpiDsInitOneObject, &Info, NULL);
+    Status = AcpiUtAcquireMutex (ACPI_MTX_NAMESPACE);
+    if (ACPI_FAILURE (Status))
+    {
+        return_ACPI_STATUS (Status);
+    }
+
+    /*
+     * We don't use AcpiWalkNamespace since we do not want to acquire
+     * the namespace reader lock.
+     */
+    Status = AcpiNsWalkNamespace (ACPI_TYPE_ANY, StartNode, ACPI_UINT32_MAX,
+                ACPI_NS_WALK_UNLOCK, AcpiDsInitOneObject, &Info, NULL);
     if (ACPI_FAILURE (Status))
     {
         ACPI_EXCEPTION ((AE_INFO, Status, "During WalkNamespace"));
     }
+    (void) AcpiUtReleaseMutex (ACPI_MTX_NAMESPACE);
 
     Status = AcpiGetTableByIndex (TableIndex, &Table);
     if (ACPI_FAILURE (Status))

source/components/executer/exconfig.c

@@ -641,13 +641,15 @@ AcpiExUnloadTable (
         }
     }
 
-    /*
-     * Delete the entire namespace under this table Node
-     * (Offset contains the TableId)
-     */
-    AcpiTbDeleteNamespaceByOwner (TableIndex);
-    (void) AcpiTbReleaseOwnerId (TableIndex);
+    /* Delete the portion of the namespace owned by this table */
 
+    Status = AcpiTbDeleteNamespaceByOwner (TableIndex);
+    if (ACPI_FAILURE (Status))
+    {
+        return_ACPI_STATUS (Status);
+    }
+
+    (void) AcpiTbReleaseOwnerId (TableIndex);
     AcpiTbSetTableLoadedFlag (TableIndex, FALSE);
 
     /* Table unloaded, remove a reference to the DdbHandle object */

source/components/namespace/nsxfeval.c

@@ -592,22 +592,41 @@ AcpiWalkNamespace (
     }
 
     /*
-     * 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 = AcpiUtAcquireReadLock (&AcpiGbl_NamespaceRwLock);
+    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 = AcpiUtAcquireMutex (ACPI_MTX_NAMESPACE);
     if (ACPI_FAILURE (Status))
     {
-        return_ACPI_STATUS (Status);
+        goto UnlockAndExit;
     }
 
     Status = AcpiNsWalkNamespace (Type, StartObject, MaxDepth,
-                    ACPI_NS_WALK_UNLOCK,
-                    UserFunction, Context, ReturnValue);
+                ACPI_NS_WALK_UNLOCK, UserFunction, Context, ReturnValue);
 
     (void) AcpiUtReleaseMutex (ACPI_MTX_NAMESPACE);
+
+UnlockAndExit:
+    (void) AcpiUtReleaseReadLock (&AcpiGbl_NamespaceRwLock);
     return_ACPI_STATUS (Status);
 }
 

source/components/tables/tbinstal.c

@@ -552,32 +552,62 @@ AcpiTbTerminate (
  *
  * PARAMETERS:  TableIndex          - Table index
  *
- * RETURN:      None
+ * RETURN:      Status
  *
  * DESCRIPTION: Delete all namespace objects created when this table was loaded.
  *
  ******************************************************************************/
 
-void
+ACPI_STATUS
 AcpiTbDeleteNamespaceByOwner (
     UINT32                  TableIndex)
 {
     ACPI_OWNER_ID           OwnerId;
+    ACPI_STATUS             Status;
 
 
-    (void) AcpiUtAcquireMutex (ACPI_MTX_TABLES);
-    if (TableIndex < AcpiGbl_RootTableList.Count)
+    ACPI_FUNCTION_TRACE (TbDeleteNamespaceByOwner);
+
+
+    Status = AcpiUtAcquireMutex (ACPI_MTX_TABLES);
+    if (ACPI_FAILURE (Status))
     {
-        OwnerId = AcpiGbl_RootTableList.Tables[TableIndex].OwnerId;
+        return_ACPI_STATUS (Status);
     }
-    else
+
+    if (TableIndex >= AcpiGbl_RootTableList.Count)
     {
+        /* The table index does not exist */
+
         (void) AcpiUtReleaseMutex (ACPI_MTX_TABLES);
-        return;
+        return_ACPI_STATUS (AE_NOT_EXIST);
     }
 
+    /* Get the owner ID for this table, used to delete namespace nodes */
+
+    OwnerId = AcpiGbl_RootTableList.Tables[TableIndex].OwnerId;
     (void) AcpiUtReleaseMutex (ACPI_MTX_TABLES);
+
+    /*
+     * Need to acquire the namespace writer lock to prevent interference
+     * with any concurrent namespace walks. The interpreter must be
+     * released during the deletion since the acquisition of the deletion
+     * lock may block, and also since the execution of a namespace walk
+     * must be allowed to use the interpreter.
+     */
+    AcpiUtReleaseMutex (ACPI_MTX_INTERPRETER);
+    Status = AcpiUtAcquireWriteLock (&AcpiGbl_NamespaceRwLock);
+
     AcpiNsDeleteNamespaceByOwner (OwnerId);
+    if (ACPI_FAILURE (Status))
+    {
+        return_ACPI_STATUS (Status);
+    }
+
+    AcpiUtReleaseWriteLock (&AcpiGbl_NamespaceRwLock);
+
+    Status = AcpiUtAcquireMutex (ACPI_MTX_INTERPRETER);
+    return_ACPI_STATUS (Status);
 }
 
 

source/components/utilities/utlock.c

@@ -0,0 +1,277 @@
+/******************************************************************************
+ *
+ * Module Name: utlock - Reader/Writer lock interfaces
+ *
+ *****************************************************************************/
+
+/******************************************************************************
+ *
+ * 1. Copyright Notice
+ *
+ * Some or all of this work - Copyright (c) 1999 - 2009, Intel Corp.
+ * All rights reserved.
+ *
+ * 2. License
+ *
+ * 2.1. This is your license from Intel Corp. under its intellectual property
+ * rights.  You may have additional license terms from the party that provided
+ * you this software, covering your right to use that party's intellectual
+ * property rights.
+ *
+ * 2.2. Intel grants, free of charge, to any person ("Licensee") obtaining a
+ * copy of the source code appearing in this file ("Covered Code") an
+ * irrevocable, perpetual, worldwide license under Intel's copyrights in the
+ * base code distributed originally by Intel ("Original Intel Code") to copy,
+ * make derivatives, distribute, use and display any portion of the Covered
+ * Code in any form, with the right to sublicense such rights; and
+ *
+ * 2.3. Intel grants Licensee a non-exclusive and non-transferable patent
+ * license (with the right to sublicense), under only those claims of Intel
+ * patents that are infringed by the Original Intel Code, to make, use, sell,
+ * offer to sell, and import the Covered Code and derivative works thereof
+ * solely to the minimum extent necessary to exercise the above copyright
+ * license, and in no event shall the patent license extend to any additions
+ * to or modifications of the Original Intel Code.  No other license or right
+ * is granted directly or by implication, estoppel or otherwise;
+ *
+ * The above copyright and patent license is granted only if the following
+ * conditions are met:
+ *
+ * 3. Conditions
+ *
+ * 3.1. Redistribution of Source with Rights to Further Distribute Source.
+ * Redistribution of source code of any substantial portion of the Covered
+ * Code or modification with rights to further distribute source must include
+ * the above Copyright Notice, the above License, this list of Conditions,
+ * and the following Disclaimer and Export Compliance provision.  In addition,
+ * Licensee must cause all Covered Code to which Licensee contributes to
+ * contain a file documenting the changes Licensee made to create that Covered
+ * Code and the date of any change.  Licensee must include in that file the
+ * documentation of any changes made by any predecessor Licensee.  Licensee
+ * must include a prominent statement that the modification is derived,
+ * directly or indirectly, from Original Intel Code.
+ *
+ * 3.2. Redistribution of Source with no Rights to Further Distribute Source.
+ * Redistribution of source code of any substantial portion of the Covered
+ * Code or modification without rights to further distribute source must
+ * include the following Disclaimer and Export Compliance provision in the
+ * documentation and/or other materials provided with distribution.  In
+ * addition, Licensee may not authorize further sublicense of source of any
+ * portion of the Covered Code, and must include terms to the effect that the
+ * license from Licensee to its licensee is limited to the intellectual
+ * property embodied in the software Licensee provides to its licensee, and
+ * not to intellectual property embodied in modifications its licensee may
+ * make.
+ *
+ * 3.3. Redistribution of Executable. Redistribution in executable form of any
+ * substantial portion of the Covered Code or modification must reproduce the
+ * above Copyright Notice, and the following Disclaimer and Export Compliance
+ * provision in the documentation and/or other materials provided with the
+ * distribution.
+ *
+ * 3.4. Intel retains all right, title, and interest in and to the Original
+ * Intel Code.
+ *
+ * 3.5. Neither the name Intel nor any other trademark owned or controlled by
+ * Intel shall be used in advertising or otherwise to promote the sale, use or
+ * other dealings in products derived from or relating to the Covered Code
+ * without prior written authorization from Intel.
+ *
+ * 4. Disclaimer and Export Compliance
+ *
+ * 4.1. INTEL MAKES NO WARRANTY OF ANY KIND REGARDING ANY SOFTWARE PROVIDED
+ * HERE.  ANY SOFTWARE ORIGINATING FROM INTEL OR DERIVED FROM INTEL SOFTWARE
+ * IS PROVIDED "AS IS," AND INTEL WILL NOT PROVIDE ANY SUPPORT,  ASSISTANCE,
+ * INSTALLATION, TRAINING OR OTHER SERVICES.  INTEL WILL NOT PROVIDE ANY
+ * UPDATES, ENHANCEMENTS OR EXTENSIONS.  INTEL SPECIFICALLY DISCLAIMS ANY
+ * IMPLIED WARRANTIES OF MERCHANTABILITY, NONINFRINGEMENT AND FITNESS FOR A
+ * PARTICULAR PURPOSE.
+ *
+ * 4.2. IN NO EVENT SHALL INTEL HAVE ANY LIABILITY TO LICENSEE, ITS LICENSEES
+ * OR ANY OTHER THIRD PARTY, FOR ANY LOST PROFITS, LOST DATA, LOSS OF USE OR
+ * COSTS OF PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES, OR FOR ANY INDIRECT,
+ * SPECIAL OR CONSEQUENTIAL DAMAGES ARISING OUT OF THIS AGREEMENT, UNDER ANY
+ * CAUSE OF ACTION OR THEORY OF LIABILITY, AND IRRESPECTIVE OF WHETHER INTEL
+ * HAS ADVANCE NOTICE OF THE POSSIBILITY OF SUCH DAMAGES.  THESE LIMITATIONS
+ * SHALL APPLY NOTWITHSTANDING THE FAILURE OF THE ESSENTIAL PURPOSE OF ANY
+ * LIMITED REMEDY.
+ *
+ * 4.3. Licensee shall not export, either directly or indirectly, any of this
+ * software or system incorporating such software without first obtaining any
+ * required license or other approval from the U. S. Department of Commerce or
+ * any other agency or department of the United States Government.  In the
+ * event Licensee exports any such software from the United States or
+ * re-exports any such software from a foreign destination, Licensee shall
+ * ensure that the distribution and export/re-export of the software is in
+ * compliance with all laws, regulations, orders, or other restrictions of the
+ * U.S. Export Administration Regulations. Licensee agrees that neither it nor
+ * any of its subsidiaries will export/re-export any technical data, process,
+ * software, or service, directly or indirectly, to any country for which the
+ * United States government or any agency thereof requires an export license,
+ * other governmental approval, or letter of assurance, without first obtaining
+ * such license, approval or letter.
+ *
+ *****************************************************************************/
+
+#define __UTLOCK_C__
+
+#include "acpi.h"
+#include "accommon.h"
+
+
+#define _COMPONENT          ACPI_UTILITIES
+        ACPI_MODULE_NAME    ("utlock")
+
+
+/*******************************************************************************
+ *
+ * FUNCTION:    AcpiUtCreateRwLock
+ *              AcpiUtDeleteRwLock
+ *
+ * PARAMETERS:  Lock                - Pointer to a valid RW lock
+ *
+ * RETURN:      Status
+ *
+ * DESCRIPTION: Reader/writer lock creation and deletion interfaces.
+ *
+ ******************************************************************************/
+
+ACPI_STATUS
+AcpiUtCreateRwLock (
+    ACPI_RW_LOCK            *Lock)
+{
+    ACPI_STATUS             Status;
+
+
+    Lock->NumReaders = 0;
+    Status = AcpiOsCreateMutex (&Lock->ReaderMutex);
+    if (ACPI_FAILURE (Status))
+    {
+        return (Status);
+    }
+
+    Status = AcpiOsCreateMutex (&Lock->WriterMutex);
+    return (Status);
+}
+
+
+void
+AcpiUtDeleteRwLock (
+    ACPI_RW_LOCK            *Lock)
+{
+
+    AcpiOsDeleteMutex (Lock->ReaderMutex);
+    AcpiOsDeleteMutex (Lock->WriterMutex);
+
+    Lock->NumReaders = 0;
+    Lock->ReaderMutex = NULL;
+    Lock->WriterMutex = NULL;
+}
+
+
+/*******************************************************************************
+ *
+ * FUNCTION:    AcpiUtAcquireReadLock
+ *              AcpiUtReleaseReadLock
+ *
+ * PARAMETERS:  Lock                - Pointer to a valid RW lock
+ *
+ * RETURN:      Status
+ *
+ * DESCRIPTION: Reader interfaces for reader/writer locks. On acquisition,
+ *              only the first reader acquires the write mutex. On release,
+ *              only the last reader releases the write mutex. Although this
+ *              algorithm can in theory starve writers, this should not be a
+ *              problem with ACPICA since the subsystem is infrequently used
+ *              in comparison to (for example) an I/O system.
+ *
+ ******************************************************************************/
+
+ACPI_STATUS
+AcpiUtAcquireReadLock (
+    ACPI_RW_LOCK            *Lock)
+{
+    ACPI_STATUS             Status;
+
+
+    Status = AcpiOsAcquireMutex (Lock->ReaderMutex, ACPI_WAIT_FOREVER);
+    if (ACPI_FAILURE (Status))
+    {
+        return (Status);
+    }
+
+    /* Acquire the write lock only for the first reader */
+
+    Lock->NumReaders++;
+    if (Lock->NumReaders == 1)
+    {
+        Status = AcpiOsAcquireMutex (Lock->WriterMutex, ACPI_WAIT_FOREVER);
+    }
+
+    AcpiOsReleaseMutex (Lock->ReaderMutex);
+    return (Status);
+}
+
+
+ACPI_STATUS
+AcpiUtReleaseReadLock (
+    ACPI_RW_LOCK            *Lock)
+{
+    ACPI_STATUS             Status;
+
+
+    Status = AcpiOsAcquireMutex (Lock->ReaderMutex, ACPI_WAIT_FOREVER);
+    if (ACPI_FAILURE (Status))
+    {
+        return (Status);
+    }
+
+    /* Release the write lock only for the very last reader */
+
+    Lock->NumReaders--;
+    if (Lock->NumReaders == 0)
+    {
+        AcpiOsReleaseMutex (Lock->WriterMutex);
+    }
+
+    AcpiOsReleaseMutex (Lock->ReaderMutex);
+    return (Status);
+}
+
+
+/*******************************************************************************
+ *
+ * FUNCTION:    AcpiUtAcquireWriteLock
+ *              AcpiUtReleaseWriteLock
+ *
+ * PARAMETERS:  Lock                - Pointer to a valid RW lock
+ *
+ * RETURN:      Status
+ *
+ * DESCRIPTION: Writer interfaces for reader/writer locks. Simply acquire or
+ *              release the writer mutex associated with the lock. Acquisition
+ *              of the lock is fully exclusive and will block all readers and
+ *              writers until it is released.
+ *
+ ******************************************************************************/
+
+ACPI_STATUS
+AcpiUtAcquireWriteLock (
+    ACPI_RW_LOCK            *Lock)
+{
+    ACPI_STATUS             Status;
+
+
+    Status = AcpiOsAcquireMutex (Lock->WriterMutex, ACPI_WAIT_FOREVER);
+    return (Status);
+}
+
+
+void
+AcpiUtReleaseWriteLock (
+    ACPI_RW_LOCK            *Lock)
+{
+
+    AcpiOsReleaseMutex (Lock->WriterMutex);
+}
+

source/components/utilities/utmutex.c

@@ -141,7 +141,8 @@ AcpiUtDeleteMutex (
  *
  * RETURN:      Status
  *
- * DESCRIPTION: Create the system mutex objects.
+ * DESCRIPTION: Create the system mutex objects. This includes mutexes,
+ *              spin locks, and reader/writer locks.
  *
  ******************************************************************************/
 
@@ -156,9 +157,8 @@ AcpiUtMutexInitialize (
     ACPI_FUNCTION_TRACE (UtMutexInitialize);
 
 
-    /*
-     * Create each of the predefined mutex objects
-     */
+    /* Create each of the predefined mutex objects */
+
     for (i = 0; i < ACPI_NUM_MUTEX; i++)
     {
         Status = AcpiUtCreateMutex (i);
@@ -177,6 +177,14 @@ AcpiUtMutexInitialize (
     }
 
     Status = AcpiOsCreateLock (&AcpiGbl_HardwareLock);
+    if (ACPI_FAILURE (Status))
+    {
+        return_ACPI_STATUS (Status);
+    }
+
+    /* Create the reader/writer lock for namespace access */
+
+    Status = AcpiUtCreateRwLock (&AcpiGbl_NamespaceRwLock);
     return_ACPI_STATUS (Status);
 }
 
@@ -189,7 +197,8 @@ AcpiUtMutexInitialize (
  *
  * RETURN:      None.
  *
- * DESCRIPTION: Delete all of the system mutex objects.
+ * DESCRIPTION: Delete all of the system mutex objects. This includes mutexes,
+ *              spin locks, and reader/writer locks.
  *
  ******************************************************************************/
 
@@ -203,9 +212,8 @@ AcpiUtMutexTerminate (
     ACPI_FUNCTION_TRACE (UtMutexTerminate);
 
 
-    /*
-     * Delete each predefined mutex object
-     */
+    /* Delete each predefined mutex object */
+
     for (i = 0; i < ACPI_NUM_MUTEX; i++)
     {
         (void) AcpiUtDeleteMutex (i);
@@ -215,6 +223,10 @@ AcpiUtMutexTerminate (
 
     AcpiOsDeleteLock (AcpiGbl_GpeLock);
     AcpiOsDeleteLock (AcpiGbl_HardwareLock);
+
+    /* Delete the reader/writer lock */
+
+    AcpiUtDeleteRwLock (&AcpiGbl_NamespaceRwLock);
     return_VOID;
 }
 

source/include/acglobal.h

@@ -247,6 +247,10 @@ ACPI_EXTERN BOOLEAN                     AcpiGbl_GlobalLockPresent;
 ACPI_EXTERN ACPI_SPINLOCK               AcpiGbl_GpeLock;      /* For GPE data structs and registers */
 ACPI_EXTERN ACPI_SPINLOCK               AcpiGbl_HardwareLock; /* For ACPI H/W except GPE registers */
 
+/* Reader/Writer lock is used for namespace walk and dynamic table unload */
+
+ACPI_EXTERN ACPI_RW_LOCK                AcpiGbl_NamespaceRwLock;
+
 
 /*****************************************************************************
  *

source/include/aclocal.h

@@ -185,6 +185,16 @@ static char                 *AcpiGbl_MutexNames[ACPI_NUM_MUTEX] =
 #endif
 #endif
 
+/* Lock structure for reader/writer interfaces */
+
+typedef struct acpi_rw_lock
+{
+    ACPI_MUTEX              WriterMutex;
+    ACPI_MUTEX              ReaderMutex;
+    UINT32                  NumReaders;
+
+} ACPI_RW_LOCK;
+
 
 /*
  * Predefined handles for spinlocks used within the subsystem.

source/include/actables.h

@@ -177,7 +177,7 @@ void
 AcpiTbTerminate (
     void);
 
-void
+ACPI_STATUS
 AcpiTbDeleteNamespaceByOwner (
     UINT32                  TableIndex);
 

source/include/acutils.h

@@ -577,6 +577,33 @@ AcpiUtExecute_Sxds (
     ACPI_NAMESPACE_NODE     *DeviceNode,
     UINT8                   *Highest);
 
+/*
+ * utlock - reader/writer locks
+ */
+ACPI_STATUS
+AcpiUtCreateRwLock (
+    ACPI_RW_LOCK            *Lock);
+
+void
+AcpiUtDeleteRwLock (
+    ACPI_RW_LOCK            *Lock);
+
+ACPI_STATUS
+AcpiUtAcquireReadLock (
+    ACPI_RW_LOCK            *Lock);
+
+ACPI_STATUS
+AcpiUtReleaseReadLock (
+    ACPI_RW_LOCK            *Lock);
+
+ACPI_STATUS
+AcpiUtAcquireWriteLock (
+    ACPI_RW_LOCK            *Lock);
+
+void
+AcpiUtReleaseWriteLock (
+    ACPI_RW_LOCK            *Lock);
+
 
 /*
  * utobject - internal object create/delete/cache routines

source/tools/acpisrc/astable.c

@@ -416,6 +416,7 @@ ACPI_TYPED_IDENTIFIER_TABLE           AcpiIdentifiers[] = {
     {"ACPI_ROUND_UP_TO_32_BIT",             SRC_TYPE_SIMPLE},
     {"ACPI_RSCONVERT_INFO",                 SRC_TYPE_STRUCT},
     {"ACPI_RSDUMP_INFO",                    SRC_TYPE_STRUCT},
+    {"ACPI_RW_LOCK",                        SRC_TYPE_STRUCT},
     {"ACPI_SCOPE_STATE",                    SRC_TYPE_STRUCT},
     {"ACPI_SEMAPHORE",                      SRC_TYPE_SIMPLE},
     {"ACPI_SIGNAL_FATAL_INFO",              SRC_TYPE_STRUCT},