----- On Jan 27, 2016, at 12:22 PM, Thomas Gleixner tglx@xxxxxxxxxxxxx wrote:
> On Wed, 27 Jan 2016, Mathieu Desnoyers wrote:
>> +/*
>> + * sys_getcpu_cache - setup getcpu cache for caller thread
>> + */
>> +SYSCALL_DEFINE2(getcpu_cache, int32_t __user **, cpu_cachep, int, flags)
>> +{
>> + int32_t __user *cpu_cache;
>> +
>> + if (unlikely(flags))
>> + return -EINVAL;
>> + /* Check if cpu_cache is already registered. */
>> + if (current->cpu_cache) {
>> + if (put_user(current->cpu_cache, cpu_cachep))
>> + return -EFAULT;
>> + return 0;
>> + }
>
> This is really odd. How is the caller supposed to differentiate between:
>
> 1) Get the installed cpucache pointer
>
> 2) Set the cpucache pointer
>
> We really want clearly seperated functionality here.
>
> getcpu_cache(ptr, GET_CACHEP);
>
> and
>
> getcpu_cache(ptr, SET_CACHEP);
>
> Returns -EBUSY if current->cpu_cache is already set, except we allow
> replacing the pointer.
Sounds fair. What is the recommended typing for "ptr" then ?
uint32_t ** or uint32_t * ?
It would be expected to pass a "uint32_t *" for the set
operation, but the "get" operation requires a "uint32_t **".
Also, I'd be tempted to put the GET/SET operation selector as
a first parameter.
Thanks,
Mathieu
>
> Thanks,
>
> tglx
--
Mathieu Desnoyers
EfficiOS Inc.
http://www.efficios.com
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