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SubjectRe: [PATCH v4 01/18] of: overlay: add tests to validate kfrees from overlay removal
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On 10/18/18 10:03, Rob Herring wrote:
> On Mon, Oct 15, 2018 at 07:37:21PM -0700, frowand.list@gmail.com wrote:
>> From: Frank Rowand <frank.rowand@sony.com>
>>
>> Add checks:
>> - attempted kfree due to refcount reaching zero before overlay
>> is removed
>> - properties linked to an overlay node when the node is removed
>> - node refcount > one during node removal in a changeset destroy,
>> if the node was created by the changeset
>>
>> After applying this patch, several validation warnings will be
>> reported from the devicetree unittest during boot due to
>> pre-existing devicetree bugs. The warnings will be similar to:
>>
>> OF: ERROR: of_node_release() overlay node /testcase-data/overlay-node/test-bus/test-unittest11/test-unittest111 contains unexpected properties
>> OF: ERROR: memory leak - destroy cset entry: attach overlay node /testcase-data-2/substation@100/hvac-medium-2 expected refcount 1 instead of 2. of_node_get() / of_node_put() are unbalanced for this node.
>
> These messages could be formatted more consistently. Put the path either
> at the beginning (after any prefix) or end. Beginning is more like a
> compiler error. End puts what the problem is before it's off the edge of
> the screen.

The inconsistency makes the word flow more natural, but I agree that
consistency is more important. I think I can make all the messages
say the problem first, then provide the path at the end.


>> Signed-off-by: Frank Rowand <frank.rowand@sony.com>
>> ---
>> Changes since v3:
>> - Add expected value of refcount for destroy cset entry error. Also
>> explain the cause of the error.
>>
>> drivers/of/dynamic.c | 29 +++++++++++++++++++++++++++++
>> drivers/of/overlay.c | 1 +
>> include/linux/of.h | 15 ++++++++++-----
>> 3 files changed, 40 insertions(+), 5 deletions(-)
>>
>> diff --git a/drivers/of/dynamic.c b/drivers/of/dynamic.c
>> index f4f8ed9b5454..24c97b7a050f 100644
>> --- a/drivers/of/dynamic.c
>> +++ b/drivers/of/dynamic.c
>> @@ -330,6 +330,25 @@ void of_node_release(struct kobject *kobj)
>> if (!of_node_check_flag(node, OF_DYNAMIC))
>> return;
>>
>> + if (of_node_check_flag(node, OF_OVERLAY)) {
>> +
>> + if (!of_node_check_flag(node, OF_OVERLAY_FREE_CSET)) {
>
> I worry the flags are getting unwieldy.

I considered that. I think we are still ok, and I don't have a better
solution than adding flag values. (I did have some Rube Goldberg
variations.)


>
>> + /* premature refcount of zero, do not free memory */
>> + pr_err("ERROR: memory leak %s() overlay node %pOF before free overlay changeset\n",
>> + __func__, node);
>> + return;
>> + }
>> +
>> + /*
>> + * If node->properties non-empty then properties were added
>> + * to this node either by different overlay that has not
>> + * yet been removed, or by a non-overlay mechanism.
>> + */
>> + if (node->properties)
>> + pr_err("ERROR: %s() overlay node %pOF contains unexpected properties\n",
>> + __func__, node);
>> + }
>> +
>> property_list_free(node->properties);
>> property_list_free(node->deadprops);
>>
>> @@ -434,6 +453,16 @@ struct device_node *__of_node_dup(const struct device_node *np,
>>
>> static void __of_changeset_entry_destroy(struct of_changeset_entry *ce)
>> {
>> + if (ce->action == OF_RECONFIG_ATTACH_NODE &&
>> + of_node_check_flag(ce->np, OF_OVERLAY)) {
>> + if (kref_read(&ce->np->kobj.kref) > 1) {
>> + pr_err("ERROR: memory leak - destroy cset entry: attach overlay node %pOF expected refcount 1 instead of %d. of_node_get() / of_node_put() are unbalanced for this node.\n",
>> + ce->np, kref_read(&ce->np->kobj.kref));
>> + } else {
>> + of_node_set_flag(ce->np, OF_OVERLAY_FREE_CSET);
>> + }
>> + }
>> +
>> of_node_put(ce->np);
>> list_del(&ce->node);
>> kfree(ce);
>> diff --git a/drivers/of/overlay.c b/drivers/of/overlay.c
>> index eda57ef12fd0..1176cb4b6e4e 100644
>> --- a/drivers/of/overlay.c
>> +++ b/drivers/of/overlay.c
>> @@ -373,6 +373,7 @@ static int add_changeset_node(struct overlay_changeset *ovcs,
>> return -ENOMEM;
>>
>> tchild->parent = target_node;
>> + of_node_set_flag(tchild, OF_OVERLAY);
>>
>> ret = of_changeset_attach_node(&ovcs->cset, tchild);
>> if (ret)
>> diff --git a/include/linux/of.h b/include/linux/of.h
>> index 4d25e4f952d9..aa1dafaec6ae 100644
>> --- a/include/linux/of.h
>> +++ b/include/linux/of.h
>> @@ -138,11 +138,16 @@ static inline void of_node_put(struct device_node *node) { }
>> extern struct device_node *of_stdout;
>> extern raw_spinlock_t devtree_lock;
>>
>> -/* flag descriptions (need to be visible even when !CONFIG_OF) */
>> -#define OF_DYNAMIC 1 /* node and properties were allocated via kmalloc */
>> -#define OF_DETACHED 2 /* node has been detached from the device tree */
>> -#define OF_POPULATED 3 /* device already created for the node */
>> -#define OF_POPULATED_BUS 4 /* of_platform_populate recursed to children of this node */
>> +/*
>> + * struct device_node flag descriptions
>> + * (need to be visible even when !CONFIG_OF)
>> + */
>> +#define OF_DYNAMIC 1 /* (and properties) allocated via kmalloc */
>> +#define OF_DETACHED 2 /* detached from the device tree */
>> +#define OF_POPULATED 3 /* device already created */
>> +#define OF_POPULATED_BUS 4 /* platform bus created for children */
>> +#define OF_OVERLAY 5 /* allocated for an overlay */
>> +#define OF_OVERLAY_FREE_CSET 6 /* in overlay cset being freed */
>>
>> #define OF_BAD_ADDR ((u64)-1)
>>
>> --
>> Frank Rowand <frank.rowand@sony.com>
>>
>

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