From: will.deacon@arm.com (Will Deacon)
To: linux-arm-kernel@lists.infradead.org
Subject: [PATCH 2/2] ARM: include: asm: use 'int' instead of 'unsigned long' for normal register variables within atomic.h
Date: Wed, 2 Oct 2013 11:41:58 +0100 [thread overview]
Message-ID: <20131002104158.GD28311@mudshark.cambridge.arm.com> (raw)
In-Reply-To: <524ABA20.6060106@asianux.com>
On Tue, Oct 01, 2013 at 01:03:44PM +0100, Chen Gang wrote:
> On 10/01/2013 05:01 PM, Will Deacon wrote:
> > On Tue, Oct 01, 2013 at 03:05:27AM +0100, Chen Gang wrote:
> >> OK, thanks. That means: "arm means arm 32-bit, arm64 means arm 64-bit.
> >> The current Linux kernel main line does not support arm 16-bit".
> >>
> >> Since "bringing our atomic_t ... with the atomic_t type definition", can
> >> we use 'atomic_t" instead of 'unsigned long'?
> >>
> >> And can we use 'atomic64_t" instead of 'unsigned long' in atomic64_*()?
> >
> > That's probably a bit dodgy, since they are typedefs to compound types
> > which, if ever extended, would fall to bits if we tried to pack them into a
> > single register.
> >
>
> Excuse me, my English is not quite well, I guess your meaning is: "in
> 'atomic.h', for arm/arm64, let register variables type equal to related
> atomic type: use 64-bit type if 'atomic64_t', 32-bit type if 'atomic_t'.
Sorry, I think I've confused you. This should be a simple change:
On ARM:
- The atomic_t typedef is a struct containing an int.
- The atomic64_t typedef is a struct containing a long long.
On arm64:
- The atomic_t typedef is a struct containing an int.
- The atomic64_t typedef is a struct containing a long.
Now, your first patch made the handling of atomic64_t on ARM use long long
instead of u64. That's good, because it fixes a signedness bug.
The second patch is just a clean-up, because our atomic_* functions on ARM
interchangeably use int and unsigned long when working with atomic_t types.
This can be tidied up by using int whenever we are reading or writing an
atomic_t, thus matching the type definition for that structure member.
So, for example, atomic_add does not need changing because it always uses
int to hold the atomic_t variable (the unsigned long holds the status
returned from the strex instruction). atomic_cmpxchg, however, loads the
atomic_t into oldval, so that should be int.
Given that this patch doesn't gain us anything in terms of functionality,
feel free to ignore it and I can take a look when there's a rainy day (which
should be real soon now). I also need to take a closer look at
atomic_clear_mask for arm64, because it looks broken to me.
Will
next prev parent reply other threads:[~2013-10-02 10:41 UTC|newest]
Thread overview: 44+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-09-21 11:06 [PATCH] ARM: include: asm: atomic.h: use type cast 's64' for the return value of atomic64_add_return() Chen Gang
2013-09-24 9:30 ` Will Deacon
2013-09-24 10:27 ` Russell King - ARM Linux
2013-09-24 10:37 ` Chen Gang
2013-09-24 10:30 ` Chen Gang
2013-09-25 2:25 ` [PATCH v2] ARM: include: asm: use 'long long' instead of 'u64' within atomic.h Chen Gang
2013-09-25 16:07 ` Will Deacon
2013-09-26 2:00 ` Chen Gang
2013-09-26 10:04 ` Will Deacon
2013-09-26 11:03 ` Chen Gang
2013-09-27 11:06 ` Will Deacon
2013-09-27 11:36 ` Chen Gang
2013-09-29 3:43 ` [PATCH 0/2] ARM: include: asm: change functions' and variables' types in atomic.h Chen Gang
2013-09-29 3:43 ` [PATCH 1/2] ARM: include: asm: use 'long long' instead of 'u64' within atomic.h Chen Gang
2013-09-29 3:52 ` [PATCH 2/2] ARM: include: asm: use 'int' instead of 'unsigned long' for normal register variables " Chen Gang
2013-09-30 16:11 ` Will Deacon
2013-10-01 2:05 ` Chen Gang
2013-10-01 9:01 ` Will Deacon
2013-10-01 12:03 ` Chen Gang
2013-10-02 10:41 ` Will Deacon [this message]
2013-10-02 15:19 ` Chen Gang
2013-10-03 10:05 ` Chen Gang
2013-10-03 16:32 ` Will Deacon
2013-10-04 9:51 ` Chen Gang
2013-10-04 15:37 ` Will Deacon
2013-10-04 15:42 ` Will Deacon
2013-10-04 23:55 ` Chen Gang
2013-10-05 0:11 ` Chen Gang
2013-10-08 4:10 ` Chen Gang
2013-10-08 10:34 ` Will Deacon
2013-10-08 10:56 ` [PATCH v2 0/2] ARM: include: asm: change functions' and variables' types in atomic.h Chen Gang
2013-10-08 10:57 ` [PATCH v2 1/2] ARM: include: asm: use 'long long' instead of 'u64' within atomic.h Chen Gang
2013-10-08 10:59 ` [PATCH v2 2/2] ARM: include: asm: use 'int' instead of 'unsigned long' for 'oldval' in atomic_cmpxchg() Chen Gang
2013-10-09 10:48 ` Will Deacon
2013-10-10 0:56 ` Chen Gang
2013-10-09 10:46 ` [PATCH v2 1/2] ARM: include: asm: use 'long long' instead of 'u64' within atomic.h Will Deacon
2013-10-08 11:00 ` [PATCH 2/2] ARM: include: asm: use 'int' instead of 'unsigned long' for normal register variables " Chen Gang
2013-10-08 10:33 ` Will Deacon
2013-10-08 11:29 ` Chen Gang
2013-10-08 17:49 ` Will Deacon
2013-10-09 0:18 ` Chen Gang
2013-10-09 1:22 ` Chen Gang
2013-09-30 16:07 ` [PATCH 1/2] ARM: include: asm: use 'long long' instead of 'u64' " Will Deacon
2013-10-01 2:09 ` Chen Gang
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