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Date: Tue, 14 Jan 2014 08:18:29 +0100
From: Yann Droneaud <ydroneaud@...eya.com>
To: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc: Yann Droneaud <ydroneaud@...eya.com>, linux-kernel@...r.kernel.org,
Uwe Kleine-König
<u.kleine-koenig@...gutronix.de>,
Dmitry Torokhov <dtor_core@...ritech.net>
Subject: [PATCHv2] driver core/platform: don't leak memory allocated for dma_mask
Since commit 01dcc60a7cb8, platform_device_register_full() is
available to allocate and register a platform device.
If a dma_mask is provided as part of platform_device_info,
platform_device_register_full() allocate memory for a u64
using kmalloc().
A comment in the code state that "[t]his memory isn't freed
when the device is put".
It's never a good thing to leak memory, but there's only very
few users of platform_device_info's dma_mask, and those are mostly
"static" devices that are not going to be plugged/unplugged.
So memory leak is not really an issue, but allocating 8 bytes
through kmalloc() seems overkill, so this patch moves dma_mask
after the platform_device struct, dynamically allocated along
the name buffer.
With dma_mask part of the memory allocated for the platform_device
struct, like name buffer, it will be released with it:
no memory leak, no small allocation.
The drawback is the additional code needed to handle
dma_mask allocation:
Before (on next-20140113 with gcc-4.8):
text data bss dec hex filename
5600 472 32 6104 17d8 obj-arm/drivers/base/platform.o
5927 532 32 6491 195b obj-i386/drivers/base/platform.o
7036 960 48 8044 1f6c obj-x86_64/drivers/base/platform.o
After:
text data bss dec hex filename
5668 472 32 6172 181c obj-arm/drivers/base/platform.o
6007 532 32 6571 19ab obj-i386/drivers/base/platform.o
7132 960 48 8140 1fcc obj-x86_64/drivers/base/platform.o
Changes from v1 [1]:
- remove unneeded kfree() from error path
- add reference to author/commit adding allocation of dmamask
Changes from v0 [2]:
- small rewrite to squeeze the patch to a bare minimal
[1] http://lkml.kernel.org/r/1389649085-7365-1-git-send-email-ydroneaud@opteya.com
https://patchwork.kernel.org/patch/3480961/
[2] http://lkml.kernel.org/r/1386886207-2735-1-git-send-email-ydroneaud@opteya.com
Cc: Uwe Kleine-König <u.kleine-koenig@...gutronix.de>
Cc: Dmitry Torokhov <dtor_core@...ritech.net>
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Signed-off-by: Yann Droneaud <ydroneaud@...eya.com>
---
Hi Greg,
> Why haven't you cc:ed the author of that comment? He would be best to
> evaluate if this patch is good enough or not.
>
I must admit I was a bit lazy: I've tried ./script/get_maintainer.pl --git / --git-blame
but the results scare me, so I've send the patch to the maintainer only. (And somehow
I've thought you wrote that comment).
> And is leaking that memory really an issue? As you point out, these
> aren't devices that are going to go away (I'd argue that no platform
> device should ever be a removable device, but that's a longer
> argument...)
>
I've seen some removable platform driver ... and, in fact, wrote some:
when writing/testing it, being able to remove the devices/driver is a must.
> Please resend and cc: all of the needed developers.
>
Thanks for the advice.
Regards.
drivers/base/platform.c | 83 ++++++++++++++++++++++++++++++++++++-------------
1 file changed, 62 insertions(+), 21 deletions(-)
diff --git a/drivers/base/platform.c b/drivers/base/platform.c
index 3a94b799f166..6e3e639fb886 100644
--- a/drivers/base/platform.c
+++ b/drivers/base/platform.c
@@ -157,7 +157,7 @@ EXPORT_SYMBOL_GPL(platform_add_devices);
struct platform_object {
struct platform_device pdev;
- char name[1];
+ char payload[0];
};
/**
@@ -186,6 +186,25 @@ static void platform_device_release(struct device *dev)
kfree(pa);
}
+static struct platform_object *platform_object_alloc(size_t payload)
+{
+ struct platform_object *pa;
+
+ pa = kzalloc(sizeof(*pa) + payload, GFP_KERNEL);
+
+ return pa;
+}
+
+static void platform_object_init(struct platform_object *pa,
+ const char *name, int id)
+{
+ pa->pdev.name = name;
+ pa->pdev.id = id;
+ device_initialize(&pa->pdev.dev);
+ pa->pdev.dev.release = platform_device_release;
+ arch_setup_pdev_archdata(&pa->pdev);
+}
+
/**
* platform_device_alloc - create a platform device
* @name: base name of the device we're adding
@@ -198,14 +217,10 @@ struct platform_device *platform_device_alloc(const char *name, int id)
{
struct platform_object *pa;
- pa = kzalloc(sizeof(struct platform_object) + strlen(name), GFP_KERNEL);
+ pa = platform_object_alloc(strlen(name) + 1);
if (pa) {
- strcpy(pa->name, name);
- pa->pdev.name = pa->name;
- pa->pdev.id = id;
- device_initialize(&pa->pdev.dev);
- pa->pdev.dev.release = platform_device_release;
- arch_setup_pdev_archdata(&pa->pdev);
+ strcpy(pa->payload, name);
+ platform_object_init(pa, pa->payload, id);
}
return pa ? &pa->pdev : NULL;
@@ -213,6 +228,39 @@ struct platform_device *platform_device_alloc(const char *name, int id)
EXPORT_SYMBOL_GPL(platform_device_alloc);
/**
+ * platform_device_dmamask_alloc - create a platform device suitable to hold a dmamask
+ * @name: base name of the device we're adding
+ * @id: instance id
+ *
+ * Create a platform device object which can have other objects attached
+ * to it, and which will have attached objects freed when it is released.
+ */
+static struct platform_device *platform_device_dmamask_alloc(const char *name,
+ int id)
+{
+ struct platform_object *pa;
+ const size_t padding = (((offsetof(struct platform_object, payload) +
+ (__alignof__(u64) - 1)) &
+ ~(__alignof__(u64) - 1)) -
+ offsetof(struct platform_object, payload));
+
+ pa = platform_object_alloc(padding + sizeof(u64) + strlen(name) + 1);
+ if (pa) {
+ char *payload = pa->payload + padding;
+ /*
+ * Conceptually dma_mask in struct device should not be a pointer.
+ * See http://thread.gmane.org/gmane.linux.kernel.pci/9081
+ */
+ pa->pdev.dev.dma_mask = (void *)payload;
+ payload += sizeof(u64);
+ strcpy(payload, name);
+ platform_object_init(pa, payload, id);
+ }
+
+ return pa ? &pa->pdev : NULL;
+}
+
+/**
* platform_device_add_resources - add resources to a platform device
* @pdev: platform device allocated by platform_device_alloc to add resources to
* @res: set of resources that needs to be allocated for the device
@@ -427,7 +475,12 @@ struct platform_device *platform_device_register_full(
int ret = -ENOMEM;
struct platform_device *pdev;
- pdev = platform_device_alloc(pdevinfo->name, pdevinfo->id);
+ if (!pdevinfo->dma_mask)
+ pdev = platform_device_alloc(pdevinfo->name, pdevinfo->id);
+ else
+ pdev = platform_device_dmamask_alloc(pdevinfo->name,
+ pdevinfo->id);
+
if (!pdev)
goto err_alloc;
@@ -435,17 +488,6 @@ struct platform_device *platform_device_register_full(
ACPI_COMPANION_SET(&pdev->dev, pdevinfo->acpi_node.companion);
if (pdevinfo->dma_mask) {
- /*
- * This memory isn't freed when the device is put,
- * I don't have a nice idea for that though. Conceptually
- * dma_mask in struct device should not be a pointer.
- * See http://thread.gmane.org/gmane.linux.kernel.pci/9081
- */
- pdev->dev.dma_mask =
- kmalloc(sizeof(*pdev->dev.dma_mask), GFP_KERNEL);
- if (!pdev->dev.dma_mask)
- goto err;
-
*pdev->dev.dma_mask = pdevinfo->dma_mask;
pdev->dev.coherent_dma_mask = pdevinfo->dma_mask;
}
@@ -464,7 +506,6 @@ struct platform_device *platform_device_register_full(
if (ret) {
err:
ACPI_COMPANION_SET(&pdev->dev, NULL);
- kfree(pdev->dev.dma_mask);
err_alloc:
platform_device_put(pdev);
--
1.8.4.2
--
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