On Mon, Aug 17, 2020 at 10:02:05PM +0200, Bartosz Golaszewski wrote:

On Mon, Aug 17, 2020 at 7:43 PM Andy Shevchenko
[off-list ref] wrote:

quoted

On Mon, Aug 17, 2020 at 07:05:33PM +0200, Bartosz Golaszewski wrote:

quoted

From: Bartosz Golaszewski <redacted>

...

quoted

quoted

+static struct devres *to_devres(void *data)
+{
+     return (struct devres *)((u8 *)data - ALIGN(sizeof(struct devres),
+                                                 ARCH_KMALLOC_MINALIGN));

Do you really need both explicit castings?

Yeah, we can probably drop the (struct devres *) here.

void * -> u8 * here is also not needed, it is considered byte access IIRC.

quoted

quoted

+}

...

quoted

 - hasn't gone while you run a ksize()?

At some point you need to draw a line. In the end: how do you
guarantee a devres buffer hasn't been freed when you're using it? In
my comment to the previous version of this patch I clarified that we
need to protect all modifications of the devres linked list - we must
not realloc a chunk that contains the links without taking the
spinlock but also we must not call alloc() funcs with GFP_KERNEL with
spinlock taken. The issue we could run into is: someone modifies the
linked list by adding/removing other managed resources, not modifying
this one.

The way this function works now guarantees it but other than that:
it's up to the users to not free memory they're actively using.

Thanks for clarification. I agree.

-- 
With Best Regards,
Andy Shevchenko



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