From: gang.chen@asianux•com (Chen Gang)
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, 02 Oct 2013 23:19:29 +0800 [thread overview]
Message-ID: <524C3981.20307@asianux.com> (raw)
In-Reply-To: <20131002104158.GD28311@mudshark.cambridge.arm.com>
On 10/02/2013 06:41 PM, Will Deacon wrote:
> 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:
>
Oh, no sorry, my English is really not quite well, and I am not quite
familiar with arm (even inline assembly language grammar, which I
should familiar).
I really should see the deals about it.
> 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.
>
Yeah.
> 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.
>
OK, thanks.
> 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.
>
OK, thank you for your details information, originally I did not check
the inline assembly code in details (which I should do).
And what you said above is reasonable to me.
After a check, I think for atomic64_*() in arm have no this kind of
issue.
> 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.
>
OK, thanks.
Hmm... after read arm64 again, at least for me, it has no this kind of
issue.
:-)
> Will
>
>
So the related patch is below (still based on Patch 1):
-----------------------------patch begin--------------------------------
arm/include/asm/atomic.h: use 'int' instead of 'unsigned long' for 'oldval' in atomic_cmpxchg().
For atomic_cmpxchg(), the type of 'oldval' need be 'int' to match the
type of "*ptr" (used by 'ldrex' instruction) and 'old' (used by 'teq'
instruction).
Signed-off-by: Chen Gang <gang.chen@asianux•com>
---
arch/arm/include/asm/atomic.h | 3 ++-
1 files changed, 2 insertions(+), 1 deletions(-)
diff --git a/arch/arm/include/asm/atomic.h b/arch/arm/include/asm/atomic.h
index a715ac0..9ee7e01 100644
--- a/arch/arm/include/asm/atomic.h
+++ b/arch/arm/include/asm/atomic.h
@@ -114,7 +114,8 @@ static inline int atomic_sub_return(int i, atomic_t *v)
static inline int atomic_cmpxchg(atomic_t *ptr, int old, int new)
{
- unsigned long oldval, res;
+ int oldval;
+ unsigned long res;
smp_mb();
--
1.7.7.6
-----------------------------patch end----------------------------------
Thanks.
--
Chen Gang
next prev parent reply other threads:[~2013-10-02 15:19 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
2013-10-02 15:19 ` Chen Gang [this message]
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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