Re: [Xen-devel] [RFC v4 1/8] Port WARN_ON_ONCE() from Linux

[Sameer Goel <sameer.goel@xxxxxxxxxx>]

On 1/23/2018 9:13 AM, Wei Liu wrote:
> On Mon, Dec 18, 2017 at 08:16:56PM -0700, Sameer Goel wrote:
>> Port WARN_ON_ONCE macro from Linux.
>>
>> Signed-off-by: Sameer Goel <sameer.goel@xxxxxxxxxx>
>> ---
>>  xen/include/xen/lib.h | 11 +++++++++++
>>  1 file changed, 11 insertions(+)
>>
>> diff --git a/xen/include/xen/lib.h b/xen/include/xen/lib.h
>> index ed00ae1379..83206c0848 100644
>> --- a/xen/include/xen/lib.h
>> +++ b/xen/include/xen/lib.h
>> @@ -11,6 +11,17 @@
>>  #define BUG_ON(p)  do { if (unlikely(p)) BUG();  } while (0)
>>  #define WARN_ON(p) do { if (unlikely(p)) WARN(); } while (0)
>>  
>> +#define WARN_ON_ONCE(p)     ({                          \
>> +    static bool __section(".data.unlikely") __warned; \
> You introduced a new section without corresponding changes to
> {arm,x86}/xen.lds.S
I will fix this.
>
>> +    int __ret_warn_once = !!(p);                    \
>> +                                                    \
>> +    if (unlikely(__ret_warn_once && !__warned)) {   \
>> +        __warned = true;                            \
>> +        WARN_ON(1);                                 \
> This isn't really a direct port from Linux. At this point I wonder why
> you didn't use WARN() directly?
>
> Wei.
>
>> +    }                                               \
>> +    unlikely(__ret_warn_once);                      \
>> +})
>> +
>>  #if __GNUC__ > 4 || (__GNUC__ == 4 && __GNUC_MINOR__ >= 6)
>>  /* Force a compilation error if condition is true */
>>  #define BUILD_BUG_ON(cond) ({ _Static_assert(!(cond), "!(" #cond ")"); })
>> -- 
>> 2.14.1
>>
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