| Message ID | 20180708175621.6951-1-abrodkin@synopsys.com |
|---|---|
| State | New |
| Headers | show |
| Series | [v2] devres: Really align data field to unsigned long long | expand |
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 <abrodkin@synopsys.com> > Cc: Thomas Gleixner <tglx@linutronix.de> > Cc: stable@vger.kernel.org > --- > > 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 <greg@kroah.com>: > > 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 <abrodkin@synopsys.com> > > Cc: Thomas Gleixner <tglx@linutronix.de> > > Cc: stable@vger.kernel.org > > --- > > > > 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 <greg@kroah.com>: > > > > 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 <abrodkin@synopsys.com> > > > Cc: Thomas Gleixner <tglx@linutronix.de> > > > Cc: stable@vger.kernel.org > > > --- > > > > > > 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
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 {
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 <abrodkin@synopsys.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: stable@vger.kernel.org --- Changes v1 -> v2: * Reworded commit message * Inserted comment right in source [Thomas] drivers/base/devres.c | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-)