can the scheduler decide to schedule an interrupted but runnable thread on another CPU core? What are the implications for code?

[Andrey Chernov]

On 15.02.2014 4:11, John-Mark Gurney wrote:
>>> This is code example from cpuminer port, in case you are interested, it is very simple:
>>>
>>> static inline void affine_to_cpu(int id, int cpu)
>>> {
>>>         cpuset_t set;
>>>         CPU_ZERO(&set);
>>>         CPU_SET(cpu, &set);
>>>         cpuset_setaffinity(CPU_LEVEL_WHICH, CPU_WHICH_CPUSET, -1, sizeof(cpuset_t), &set);
>>
>> I think that CPU_WHICH_TID should have been used here.
> 
> I agree...  cpuset(2):
>      The which argument determines how the value of id is interpreted and is
>      of type cpuwhich_t.  The which argument may have the following values:
> 
>            CPU_WHICH_TID       id is lwpid_t (thread id)
>            CPU_WHICH_PID       id is pid_t (process id)
>            CPU_WHICH_CPUSET    id is a cpusetid_t (cpuset id)
>            CPU_WHICH_IRQ       id is an irq number
> 
>      An id of '-1' may be used with a which of CPU_WHICH_TID, CPU_WHICH_PID,
>      or CPU_WHICH_CPUSET to mean the current thread, process, or current
>      thread's cpuset.  All cpuset syscalls allow this usage.

The question still remains: why SCHED_ULE and SCHED_4BSD do different
things here on CPU_WHICH_CPUSET == -1 (current thread's cpuset)? It
looks like SCHED_ULE changes per/process mask while SCHED_4BSD change
per/thread mask in that case.

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