Hi Vineet,
On Mon, 2018-07-09 at 11:27 -0700, Vineet Gupta wrote:
On 07/09/2018 03:23 AM, Alexey Brodkin wrote:
Hi David,
On Mon, 2018-07-09 at 10:18 +0000, David Laight wrote:
From: Alexey Brodkin
Sent: 09 July 2018 11:00
...
That's a good idea indeed but it doesn't solve the problem with struct devres_node. Consider the following snippet: -------------------------------->8------------------------------- struct mystruct { atomic64_t myvar; }
struct mystruct *p; p = devm_kzalloc(dev, sizeof(*p), GFP_KERNEL); -------------------------------->8-------------------------------
Here myvar address will match address of "data" member of struct devres_node. So if "data" is has offset of 12 bytes from the beginning of a page then myvar won't be 64-bit aligned regardless of myvar's attribute, right?
...
- unsigned long long data[]; /* guarantee ull alignment */
Ahh, that line should be: u8 data[] __aligned(8); /* Guarantee 64bit alignment */
And that pretty much what I suggested in my initial patch :)
For the record x86 has exactly the same atomic64_t as you suggested, see https://elixir.bootlin.com/linux/latest/source/arch/x86/include/asm/atomic64...: ---------------------->8------------------ typedef struct { u64 __aligned(8) counter; } atomic64_t; ---------------------->8------------------
And so does the ARC version since when the atomic64_t support was added by commit ce6365270ecd
Also, you should consider using the pre-canned type aligned_u64.
typedef struct { aligned_u64 counter; ^^^^^^^^^^^ } atomic64_t;
As Peter mentioned earlier atomic is signed, see: http://lists.infradead.org/pipermail/linux-snps-arc/2018-July/004030.html
So looks like we need this fix for ARC instead: --------------------------------->8---------------------------- diff --git a/arch/arc/include/asm/atomic.h b/arch/arc/include/asm/atomic.h index 11859287c52a..ef94b7371de6 100644 --- a/arch/arc/include/asm/atomic.h +++ b/arch/arc/include/asm/atomic.h @@ -367,7 +367,7 @@ ATOMIC_OPS(xor, ^=, CTOP_INST_AXOR_DI_R2_R2_R3) */
typedef struct { - aligned_u64 counter; + long long __aligned(8) counter; } atomic64_t;
#define ATOMIC64_INIT(a) { (a) } --------------------------------->8----------------------------
-Alexey