Depending on ABI "long long" type of a particular 32-bit CPU
might be aligned by either word (32-bits) or double word (64-bits).
Make sure "data" is really 64-bit aligned for any 32-bit CPU.
At least for 32-bit ARC cores ABI requires "long long" types
to be aligned by normal 32-bit word. This makes "data" field aligned to
12 bytes. Which is still OK as long as we use 32-bit data only.
But once we want to use native atomic64_t type (i.e. when we use special
instructions LLOCKD/SCONDD for accessing 64-bit data) we easily hit
misaligned access exception.
That's because even on CPUs capable of non-aligned data access LL/SC
instructions require strict alignment.
Signed-off-by: Alexey Brodkin <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: [email protected]
---
Changes v1 -> v2:
* Reworded commit message
* Inserted comment right in source [Thomas]
drivers/base/devres.c | 8 ++++++--
1 file changed, 6 insertions(+), 2 deletions(-)
diff --git a/drivers/base/devres.c b/drivers/base/devres.c
index f98a097e73f2..466fa59c866a 100644
--- a/drivers/base/devres.c
+++ b/drivers/base/devres.c
@@ -24,8 +24,12 @@ struct devres_node {
struct devres {
struct devres_node node;
- /* -- 3 pointers */
- unsigned long long data[]; /* guarantee ull alignment */
+ /*
+ * Depending on ABI "long long" type of a particular 32-bit CPU
+ * might be aligned by either word (32-bits) or double word (64-bits).
+ * Make sure "data" is really 64-bit aligned for any 32-bit CPU.
+ */
+ unsigned long long data[] __aligned(sizeof(unsigned long long));
};
struct devres_group {
--
2.17.1
On Sun, Jul 08, 2018 at 08:56:21PM +0300, Alexey Brodkin wrote:
> Depending on ABI "long long" type of a particular 32-bit CPU
> might be aligned by either word (32-bits) or double word (64-bits).
> Make sure "data" is really 64-bit aligned for any 32-bit CPU.
>
> At least for 32-bit ARC cores ABI requires "long long" types
> to be aligned by normal 32-bit word. This makes "data" field aligned to
> 12 bytes. Which is still OK as long as we use 32-bit data only.
>
> But once we want to use native atomic64_t type (i.e. when we use special
> instructions LLOCKD/SCONDD for accessing 64-bit data) we easily hit
> misaligned access exception.
>
> That's because even on CPUs capable of non-aligned data access LL/SC
> instructions require strict alignment.
>
> Signed-off-by: Alexey Brodkin <[email protected]>
> Cc: Thomas Gleixner <[email protected]>
> Cc: [email protected]
> ---
>
> Changes v1 -> v2:
>
> * Reworded commit message
> * Inserted comment right in source [Thomas]
>
> drivers/base/devres.c | 8 ++++++--
> 1 file changed, 6 insertions(+), 2 deletions(-)
Always use scripts/get_maintainer.pl to properly cc: the needed
developer/maintainer. As it is, this patch is going to get dropped on
the floor, sorry...
greg k-h
Hi Greg,
вс, 8 июл. 2018 г. в 21:40, Greg KH <[email protected]>:
>
> On Sun, Jul 08, 2018 at 08:56:21PM +0300, Alexey Brodkin wrote:
> > Depending on ABI "long long" type of a particular 32-bit CPU
> > might be aligned by either word (32-bits) or double word (64-bits).
> > Make sure "data" is really 64-bit aligned for any 32-bit CPU.
> >
> > At least for 32-bit ARC cores ABI requires "long long" types
> > to be aligned by normal 32-bit word. This makes "data" field aligned to
> > 12 bytes. Which is still OK as long as we use 32-bit data only.
> >
> > But once we want to use native atomic64_t type (i.e. when we use special
> > instructions LLOCKD/SCONDD for accessing 64-bit data) we easily hit
> > misaligned access exception.
> >
> > That's because even on CPUs capable of non-aligned data access LL/SC
> > instructions require strict alignment.
> >
> > Signed-off-by: Alexey Brodkin <[email protected]>
> > Cc: Thomas Gleixner <[email protected]>
> > Cc: [email protected]
> > ---
> >
> > Changes v1 -> v2:
> >
> > * Reworded commit message
> > * Inserted comment right in source [Thomas]
> >
> > drivers/base/devres.c | 8 ++++++--
> > 1 file changed, 6 insertions(+), 2 deletions(-)
>
> Always use scripts/get_maintainer.pl to properly cc: the needed
> developer/maintainer. As it is, this patch is going to get dropped on
> the floor, sorry...
Right I was way too relaxed dealing with very generic stuff which might get
not that much of attention as more narrow topics or subsystems. But anyways
get_maintainer.pl says you're the guy so do I need to do anything extra still or
it's OK for this time?
-Alexey
On Sun, Jul 08, 2018 at 09:45:31PM +0300, Алексей Бродкин wrote:
> Hi Greg,
>
> вс, 8 июл. 2018 г. в 21:40, Greg KH <[email protected]>:
> >
> > On Sun, Jul 08, 2018 at 08:56:21PM +0300, Alexey Brodkin wrote:
> > > Depending on ABI "long long" type of a particular 32-bit CPU
> > > might be aligned by either word (32-bits) or double word (64-bits).
> > > Make sure "data" is really 64-bit aligned for any 32-bit CPU.
> > >
> > > At least for 32-bit ARC cores ABI requires "long long" types
> > > to be aligned by normal 32-bit word. This makes "data" field aligned to
> > > 12 bytes. Which is still OK as long as we use 32-bit data only.
> > >
> > > But once we want to use native atomic64_t type (i.e. when we use special
> > > instructions LLOCKD/SCONDD for accessing 64-bit data) we easily hit
> > > misaligned access exception.
> > >
> > > That's because even on CPUs capable of non-aligned data access LL/SC
> > > instructions require strict alignment.
> > >
> > > Signed-off-by: Alexey Brodkin <[email protected]>
> > > Cc: Thomas Gleixner <[email protected]>
> > > Cc: [email protected]
> > > ---
> > >
> > > Changes v1 -> v2:
> > >
> > > * Reworded commit message
> > > * Inserted comment right in source [Thomas]
> > >
> > > drivers/base/devres.c | 8 ++++++--
> > > 1 file changed, 6 insertions(+), 2 deletions(-)
> >
> > Always use scripts/get_maintainer.pl to properly cc: the needed
> > developer/maintainer. As it is, this patch is going to get dropped on
> > the floor, sorry...
>
> Right I was way too relaxed dealing with very generic stuff which might get
> not that much of attention as more narrow topics or subsystems. But anyways
> get_maintainer.pl says you're the guy so do I need to do anything extra still or
> it's OK for this time?
Please resend it properly, it is not in my patch queue anywhere...
greg k-h