drivers/edac: fix edac_device sysfs completion code

With feedback, this patch corrects operation of the kobject release operation
on kobjects, attributes and controls for the edac_device.

Cc: Alan Cox alan@lxorguk.ukuu.org.uk
Signed-off-by: Doug Thompson <dougthompson@xmission.com>
Acked-by: Greg KH <greg@kroah.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 239 insertions, 102 deletions

diff --git a/drivers/edac/edac_device_sysfs.c b/drivers/edac/edac_device_sysfs.c
index 235b4c79355d..52769ae69bd2 100644
--- a/drivers/edac/edac_device_sysfs.c
+++ b/drivers/edac/edac_device_sysfs.c
@@ -1,7 +1,8 @@
 /*
  * file for managing the edac_device class of devices for EDAC
  *
- * (C) 2007 SoftwareBitMaker(http://www.softwarebitmaker.com)
+ * (C) 2007 SoftwareBitMaker (http://www.softwarebitmaker.com)
+ *
  * This file may be distributed under the terms of the
  * GNU General Public License.
  *
@@ -10,6 +11,7 @@
  */
 
 #include <linux/ctype.h>
+#include <linux/module.h>
 
 #include "edac_core.h"
 #include "edac_module.h"
@@ -19,7 +21,6 @@
 #define to_edacdev(k) container_of(k, struct edac_device_ctl_info, kobj)
 #define to_edacdev_attr(a) container_of(a, struct edacdev_attribute, attr)
 
-/************************** edac_device sysfs code and data **************/
 
 /*
  * Set of edac_device_ctl_info attribute store/show functions
@@ -103,8 +104,8 @@ static ssize_t edac_device_ctl_poll_msec_store(struct edac_device_ctl_info
 /* edac_device_ctl_info specific attribute structure */
 struct ctl_info_attribute {
         struct attribute attr;
-         ssize_t(*show) (struct edac_device_ctl_info *, char *);
-         ssize_t(*store) (struct edac_device_ctl_info *, const char *, size_t);
+        ssize_t(*show) (struct edac_device_ctl_info *, char *);
+        ssize_t(*store) (struct edac_device_ctl_info *, const char *, size_t);
 };
 
 #define to_ctl_info(k) container_of(k, struct edac_device_ctl_info, kobj)
@@ -168,45 +169,76 @@ static struct ctl_info_attribute *device_ctrl_attr[] = {
         NULL,
 };
 
-/* Main DEVICE kobject release() function */
+/*
+ * edac_device_ctrl_master_release
+ *
+ *      called when the reference count for the 'main' kobj
+ *      for a edac_device control struct reaches zero
+ *
+ *      Reference count model:
+ *              One 'main' kobject for each control structure allocated.
+ *              That main kobj is initially set to one AND
+ *              the reference count for the EDAC 'core' module is
+ *              bumped by one, thus added 'keep in memory' dependency.
+ *
+ *              Each new internal kobj (in instances and blocks) then
+ *              bumps the 'main' kobject.
+ *
+ *              When they are released their release functions decrement
+ *              the 'main' kobj.
+ *
+ *              When the main kobj reaches zero (0) then THIS function
+ *              is called which then decrements the EDAC 'core' module.
+ *              When the module reference count reaches zero then the
+ *              module no longer has dependency on keeping the release
+ *              function code in memory and module can be unloaded.
+ *
+ *              This will support several control objects as well, each
+ *              with its own 'main' kobj.
+ */
 static void edac_device_ctrl_master_release(struct kobject *kobj)
 {
-        struct edac_device_ctl_info *edac_dev;
+        struct edac_device_ctl_info *edac_dev = to_edacdev(kobj);
 
-        edac_dev = to_edacdev(kobj);
+        debugf1("%s() control index=%d\n", __func__, edac_dev->dev_idx);
 
-        debugf1("%s()\n", __func__);
-        complete(&edac_dev->kobj_complete);
+        /* decrement the EDAC CORE module ref count */
+        module_put(edac_dev->owner);
+
+        /* free the control struct containing the 'main' kobj
+         * passed in to this routine
+         */
+        kfree(edac_dev);
 }
 
+/* ktype for the main (master) kobject */
 static struct kobj_type ktype_device_ctrl = {
         .release = edac_device_ctrl_master_release,
         .sysfs_ops = &device_ctl_info_ops,
         .default_attrs = (struct attribute **)device_ctrl_attr,
 };
 
-/**************** edac_device main kobj ctor/dtor code *********************/
-
 /*
- * edac_device_register_main_kobj
+ * edac_device_register_sysfs_main_kobj
  *
  *      perform the high level setup for the new edac_device instance
  *
  * Return:  0 SUCCESS
  *         !0 FAILURE
  */
-static int edac_device_register_main_kobj(struct edac_device_ctl_info *edac_dev)
+int edac_device_register_sysfs_main_kobj(struct edac_device_ctl_info *edac_dev)
 {
-        int err = 0;
         struct sysdev_class *edac_class;
+        int err;
 
         debugf1("%s()\n", __func__);
 
         /* get the /sys/devices/system/edac reference */
         edac_class = edac_get_edac_class();
         if (edac_class == NULL) {
-                debugf1("%s() no edac_class error=%d\n", __func__, err);
-                return err;
+                debugf1("%s() no edac_class error\n", __func__);
+                err = -ENODEV;
+                goto err_out;
         }
 
         /* Point to the 'edac_class' this instance 'reports' to */
@@ -223,42 +255,65 @@ static int edac_device_register_main_kobj(struct edac_device_ctl_info *edac_dev)
         debugf1("%s() set name of kobject to: %s\n", __func__, edac_dev->name);
         err = kobject_set_name(&edac_dev->kobj, "%s", edac_dev->name);
         if (err)
-                return err;
+                goto err_out;
+
+        /* Record which module 'owns' this control structure
+         * and bump the ref count of the module
+         */
+        edac_dev->owner = THIS_MODULE;
+
+        if (!try_module_get(edac_dev->owner)) {
+                err = -ENODEV;
+                goto err_out;
+        }
+
+        /* register */
         err = kobject_register(&edac_dev->kobj);
         if (err) {
                 debugf1("%s()Failed to register '.../edac/%s'\n",
                         __func__, edac_dev->name);
-                return err;
+                goto err_kobj_reg;
         }
 
+        /* At this point, to 'free' the control struct,
+         * edac_device_unregister_sysfs_main_kobj() must be used
+         */
+
         debugf1("%s() Registered '.../edac/%s' kobject\n",
                 __func__, edac_dev->name);
 
         return 0;
+
+        /* Error exit stack */
+err_kobj_reg:
+        module_put(edac_dev->owner);
+
+err_out:
+        return err;
 }
 
 /*
- * edac_device_unregister_main_kobj:
+ * edac_device_unregister_sysfs_main_kobj:
  *      the '..../edac/<name>' kobject
  */
-static void edac_device_unregister_main_kobj(struct edac_device_ctl_info
-                                        *edac_dev)
+void edac_device_unregister_sysfs_main_kobj(
+                                        struct edac_device_ctl_info *edac_dev)
 {
         debugf0("%s()\n", __func__);
         debugf1("%s() name of kobject is: %s\n",
                 __func__, kobject_name(&edac_dev->kobj));
 
-        init_completion(&edac_dev->kobj_complete);
-
         /*
          * Unregister the edac device's kobject and
-         * wait for reference count to reach 0.
+         * allow for reference count to reach 0 at which point
+         * the callback will be called to:
+         *   a) module_put() this module
+         *   b) 'kfree' the memory
          */
         kobject_unregister(&edac_dev->kobj);
-        wait_for_completion(&edac_dev->kobj_complete);
 }
 
-/*************** edac_dev -> instance information ***********/
+/* edac_dev -> instance information */
 
 /*
  * Set of low-level instance attribute show functions
@@ -285,8 +340,11 @@ static void edac_device_ctrl_instance_release(struct kobject *kobj)
 
         debugf1("%s()\n", __func__);
 
+        /* map from this kobj to the main control struct
+         * and then dec the main kobj count
+         */
         instance = to_instance(kobj);
-        complete(&instance->kobj_complete);
+        kobject_put(&instance->ctl->kobj);
 }
 
 /* instance specific attribute structure */
@@ -356,7 +414,7 @@ static struct kobj_type ktype_instance_ctrl = {
         .default_attrs = (struct attribute **)device_instance_attr,
 };
 
-/*************** edac_dev -> instance -> block information *********/
+/* edac_dev -> instance -> block information */
 
 /*
  * Set of low-level block attribute show functions
@@ -381,8 +439,13 @@ static void edac_device_ctrl_block_release(struct kobject *kobj)
 
         debugf1("%s()\n", __func__);
 
+        /* get the container of the kobj */
         block = to_block(kobj);
-        complete(&block->kobj_complete);
+
+        /* map from 'block kobj' to 'block->instance->controller->main_kobj'
+         * now 'release' the block kobject
+         */
+        kobject_put(&block->instance->ctl->kobj);
 }
 
 /* block specific attribute structure */
@@ -447,49 +510,60 @@ static struct kobj_type ktype_block_ctrl = {
         .default_attrs = (struct attribute **)device_block_attr,
 };
 
-/************** block ctor/dtor  code ************/
+/* block ctor/dtor  code */
 
 /*
  * edac_device_create_block
  */
 static int edac_device_create_block(struct edac_device_ctl_info *edac_dev,
                                 struct edac_device_instance *instance,
-                                int idx)
+                                struct edac_device_block *block)
 {
         int i;
         int err;
-        struct edac_device_block *block;
         struct edac_dev_sysfs_block_attribute *sysfs_attrib;
+        struct kobject *main_kobj;
 
-        block = &instance->blocks[idx];
-
-        debugf1("%s() Instance '%s' block[%d] '%s'\n",
-                __func__, instance->name, idx, block->name);
+        debugf1("%s() Instance '%s' block '%s'\n",
+                __func__, instance->name, block->name);
 
         /* init this block's kobject */
         memset(&block->kobj, 0, sizeof(struct kobject));
         block->kobj.parent = &instance->kobj;
         block->kobj.ktype = &ktype_block_ctrl;
+        block->instance = instance;
 
         err = kobject_set_name(&block->kobj, "%s", block->name);
         if (err)
                 return err;
 
+        /* bump the main kobject's reference count for this controller
+         * and this instance is dependant on the main
+         */
+        main_kobj = kobject_get(&edac_dev->kobj);
+        if (!main_kobj) {
+                err = -ENODEV;
+                goto err_out;
+        }
+
+        /* Add this block's kobject */
         err = kobject_register(&block->kobj);
         if (err) {
-                debugf1("%s()Failed to register instance '%s'\n",
+                debugf1("%s() Failed to register instance '%s'\n",
                         __func__, block->name);
-                return err;
+                kobject_put(main_kobj);
+                err = -ENODEV;
+                goto err_out;
         }
 
         /* If there are driver level block attributes, then added them
          * to the block kobject
          */
         sysfs_attrib = block->block_attributes;
-        if (sysfs_attrib != NULL) {
+        if (sysfs_attrib) {
                 for (i = 0; i < block->nr_attribs; i++) {
                         err = sysfs_create_file(&block->kobj,
-                                (struct attribute *) &sysfs_attrib[i]);
+                                (struct attribute *) sysfs_attrib);
                         if (err)
                                 goto err_on_attrib;
 
@@ -499,30 +573,41 @@ static int edac_device_create_block(struct edac_device_ctl_info *edac_dev,
 
         return 0;
 
+        /* Error unwind stack */
 err_on_attrib:
         kobject_unregister(&block->kobj);
 
+err_out:
         return err;
 }
 
 /*
- * edac_device_delete_block(edac_dev,j);
+ * edac_device_delete_block(edac_dev,block);
  */
 static void edac_device_delete_block(struct edac_device_ctl_info *edac_dev,
-                                struct edac_device_instance *instance,
-                                int idx)
+                                struct edac_device_block *block)
 {
-        struct edac_device_block *block;
+        struct edac_dev_sysfs_block_attribute *sysfs_attrib;
+        int i;
 
-        block = &instance->blocks[idx];
+        /* if this block has 'attributes' then we need to iterate over the list
+         * and 'remove' the attributes on this block
+         */
+        sysfs_attrib = block->block_attributes;
+        if (sysfs_attrib && block->nr_attribs) {
+                for (i = 0; i < block->nr_attribs; i++) {
+                        sysfs_remove_file(&block->kobj,
+                                (struct attribute *) sysfs_attrib);
+                }
+        }
 
-        /* unregister this block's kobject */
-        init_completion(&block->kobj_complete);
+        /* unregister this block's kobject, SEE:
+         *      edac_device_ctrl_block_release() callback operation
+         */
         kobject_unregister(&block->kobj);
-        wait_for_completion(&block->kobj_complete);
 }
 
-/************** instance ctor/dtor  code ************/
+/* instance ctor/dtor code */
 
 /*
  * edac_device_create_instance
@@ -534,6 +619,7 @@ static int edac_device_create_instance(struct edac_device_ctl_info *edac_dev,
         int i, j;
         int err;
         struct edac_device_instance *instance;
+        struct kobject *main_kobj;
 
         instance = &edac_dev->instances[idx];
 
@@ -543,16 +629,28 @@ static int edac_device_create_instance(struct edac_device_ctl_info *edac_dev,
         /* set this new device under the edac_device main kobject */
         instance->kobj.parent = &edac_dev->kobj;
         instance->kobj.ktype = &ktype_instance_ctrl;
+        instance->ctl = edac_dev;
 
         err = kobject_set_name(&instance->kobj, "%s", instance->name);
         if (err)
-                return err;
+                goto err_out;
+
+        /* bump the main kobject's reference count for this controller
+         * and this instance is dependant on the main
+         */
+        main_kobj = kobject_get(&edac_dev->kobj);
+        if (!main_kobj) {
+                err = -ENODEV;
+                goto err_out;
+        }
 
+        /* Formally register this instance's kobject */
         err = kobject_register(&instance->kobj);
         if (err != 0) {
                 debugf2("%s() Failed to register instance '%s'\n",
                         __func__, instance->name);
-                return err;
+                kobject_put(main_kobj);
+                goto err_out;
         }
 
         debugf1("%s() now register '%d' blocks for instance %d\n",
@@ -560,11 +658,14 @@ static int edac_device_create_instance(struct edac_device_ctl_info *edac_dev,
 
         /* register all blocks of this instance */
         for (i = 0; i < instance->nr_blocks; i++) {
-                err = edac_device_create_block(edac_dev, instance, i);
+                err = edac_device_create_block(edac_dev, instance,
+                                                &instance->blocks[i]);
                 if (err) {
+                        /* If any fail, remove all previous ones */
                         for (j = 0; j < i; j++)
-                                edac_device_delete_block(edac_dev, instance, j);
-                        return err;
+                                edac_device_delete_block(edac_dev,
+                                                        &instance->blocks[j]);
+                        goto err_release_instance_kobj;
                 }
         }
 
@@ -572,6 +673,13 @@ static int edac_device_create_instance(struct edac_device_ctl_info *edac_dev,
                 __func__, idx, instance->name);
 
         return 0;
+
+        /* error unwind stack */
+err_release_instance_kobj:
+        kobject_unregister(&instance->kobj);
+
+err_out:
+        return err;
 }
 
 /*
@@ -581,19 +689,19 @@ static int edac_device_create_instance(struct edac_device_ctl_info *edac_dev,
 static void edac_device_delete_instance(struct edac_device_ctl_info *edac_dev,
                                         int idx)
 {
-        int i;
         struct edac_device_instance *instance;
+        int i;
 
         instance = &edac_dev->instances[idx];
 
         /* unregister all blocks in this instance */
         for (i = 0; i < instance->nr_blocks; i++)
-                edac_device_delete_block(edac_dev, instance, i);
+                edac_device_delete_block(edac_dev, &instance->blocks[i]);
 
-        /* unregister this instance's kobject */
-        init_completion(&instance->kobj_complete);
+        /* unregister this instance's kobject, SEE:
+         *      edac_device_ctrl_instance_release() for callback operation
+         */
         kobject_unregister(&instance->kobj);
-        wait_for_completion(&instance->kobj_complete);
 }
 
 /*
@@ -635,39 +743,69 @@ static void edac_device_delete_instances(struct edac_device_ctl_info *edac_dev)
                 edac_device_delete_instance(edac_dev, i);
 }
 
-/******************* edac_dev sysfs ctor/dtor  code *************/
+/* edac_dev sysfs ctor/dtor  code */
 
 /*
- * edac_device_add_sysfs_attributes
+ * edac_device_add_main_sysfs_attributes
  *      add some attributes to this instance's main kobject
  */
-static int edac_device_add_sysfs_attributes(
+static int edac_device_add_main_sysfs_attributes(
                         struct edac_device_ctl_info *edac_dev)
 {
-        int err;
         struct edac_dev_sysfs_attribute *sysfs_attrib;
+        int err = 0;
 
-        /* point to the start of the array and iterate over it
-         * adding each attribute listed to this mci instance's kobject
-         */
         sysfs_attrib = edac_dev->sysfs_attributes;
-
-        while (sysfs_attrib->attr.name != NULL) {
-                err = sysfs_create_file(&edac_dev->kobj,
+        if (sysfs_attrib) {
+                /* iterate over the array and create an attribute for each
+                 * entry in the list
+                 */
+                while (sysfs_attrib->attr.name != NULL) {
+                        err = sysfs_create_file(&edac_dev->kobj,
                                 (struct attribute*) sysfs_attrib);
-                if (err)
-                        return err;
+                        if (err)
+                                goto err_out;
 
-                sysfs_attrib++;
+                        sysfs_attrib++;
+                }
         }
 
-        return 0;
+err_out:
+        return err;
+}
+
+/*
+ * edac_device_remove_main_sysfs_attributes
+ *      remove any attributes to this instance's main kobject
+ */
+static void edac_device_remove_main_sysfs_attributes(
+                        struct edac_device_ctl_info *edac_dev)
+{
+        struct edac_dev_sysfs_attribute *sysfs_attrib;
+
+        /* if there are main attributes, defined, remove them. First,
+         * point to the start of the array and iterate over it
+         * removing each attribute listed from this device's instance's kobject
+         */
+        sysfs_attrib = edac_dev->sysfs_attributes;
+        if (sysfs_attrib) {
+                while (sysfs_attrib->attr.name != NULL) {
+                        sysfs_remove_file(&edac_dev->kobj,
+                                        (struct attribute *) sysfs_attrib);
+                        sysfs_attrib++;
+                }
+        }
 }
 
 /*
  * edac_device_create_sysfs() Constructor
  *
- * Create a new edac_device kobject instance,
+ * accept a created edac_device control structure
+ * and 'export' it to sysfs. The 'main' kobj should already have been
+ * created. 'instance' and 'block' kobjects should be registered
+ * along with any 'block' attributes from the low driver. In addition,
+ * the main attributes (if any) are connected to the main kobject of
+ * the control structure.
  *
  * Return:
  *      0       Success
@@ -678,23 +816,13 @@ int edac_device_create_sysfs(struct edac_device_ctl_info *edac_dev)
         int err;
         struct kobject *edac_kobj = &edac_dev->kobj;
 
-        /* register this instance's main kobj with the edac class kobj */
-        err = edac_device_register_main_kobj(edac_dev);
-        if (err)
-                return err;
-
         debugf0("%s() idx=%d\n", __func__, edac_dev->dev_idx);
 
-        /* If the low level driver requests some sysfs entries
-         * then go create them here
-         */
-        if (edac_dev->sysfs_attributes != NULL) {
-                err = edac_device_add_sysfs_attributes(edac_dev);
-                if (err) {
-                        debugf0("%s() failed to add sysfs attribs\n",
-                                __func__);
-                        goto err_unreg_object;
-                }
+        /*  go create any main attributes callers wants */
+        err = edac_device_add_main_sysfs_attributes(edac_dev);
+        if (err) {
+                debugf0("%s() failed to add sysfs attribs\n", __func__);
+                goto err_out;
         }
 
         /* create a symlink from the edac device
@@ -705,16 +833,23 @@ int edac_device_create_sysfs(struct edac_device_ctl_info *edac_dev)
         if (err) {
                 debugf0("%s() sysfs_create_link() returned err= %d\n",
                         __func__, err);
-                goto err_unreg_object;
+                goto err_remove_main_attribs;
         }
 
-        debugf0("%s() calling create-instances, idx=%d\n",
-                __func__, edac_dev->dev_idx);
-
-        /* Create the first level instance directories */
+        /* Create the first level instance directories
+         * In turn, the nested blocks beneath the instances will
+         * be registered as well
+         */
         err = edac_device_create_instances(edac_dev);
-        if (err)
+        if (err) {
+                debugf0("%s() edac_device_create_instances() "
+                        "returned err= %d\n", __func__, err);
                 goto err_remove_link;
+        }
+
+
+        debugf0("%s() calling create-instances, idx=%d\n",
+                __func__, edac_dev->dev_idx);
 
         return 0;
 
@@ -723,26 +858,28 @@ err_remove_link:
         /* remove the sym link */
         sysfs_remove_link(&edac_dev->kobj, EDAC_DEVICE_SYMLINK);
 
-err_unreg_object:
-        edac_device_unregister_main_kobj(edac_dev);
+err_remove_main_attribs:
+        edac_device_remove_main_sysfs_attributes(edac_dev);
 
+err_out:
         return err;
 }
 
 /*
  * edac_device_remove_sysfs() destructor
  *
- * remove a edac_device instance
+ * given an edac_device struct, tear down the kobject resources
  */
 void edac_device_remove_sysfs(struct edac_device_ctl_info *edac_dev)
 {
         debugf0("%s()\n", __func__);
 
-        edac_device_delete_instances(edac_dev);
+        /* remove any main attributes for this device */
+        edac_device_remove_main_sysfs_attributes(edac_dev);
 
-        /* remove the sym link */
+        /* remove the device sym link */
         sysfs_remove_link(&edac_dev->kobj, EDAC_DEVICE_SYMLINK);
 
-        /* unregister the instance's main kobj */
-        edac_device_unregister_main_kobj(edac_dev);
+        /* walk the instance/block kobject tree, deconstructing it */
+        edac_device_delete_instances(edac_dev);
 }