/*
 * [x86] syscall.c
 */

#include <ihk/cpu.h>
#include <ihk/debug.h>
#include <cls.h>
#include <syscall.h>

//#define DEBUG_PRINT_SC

#ifdef DEBUG_PRINT_SC
#define dkprintf kprintf
#else
#define dkprintf(...)
#endif

/*
See dkprintf("BSP HW ID = %d, ", bsp_hw_id); (in ./mcos/kernel/ap.c)

Core with BSP HW ID 224 is 1st logical core of last physical core.
It                      boots first and is given SW-ID of 0

Core with BSP HW ID 0 is 1st logical core of 1st physical core. 
It                      boots next and is given  SW-ID of 1.
Core with BSP HW ID 1   boots next and is given  SW-ID of 2.
Core with BSP HW ID 2   boots next and is given  SW-ID of 3.
Core with BSP HW ID 3   boots next and is given  SW-ID of 4.
...
Core with BSP HW ID 220 is 1st logical core of 56-th physical core.
It                      boots next and is given  SW-ID of 221.
Core with BSP HW ID 221 boots next and is given  SW-ID of 222.
Core with BSP HW ID 222 boots next and is given  SW-ID of 223.
Core with BSP HW ID 223 boots next and is given  SW-ID of 224.

Core with BSP HW ID 225 is 2nd logical core of last physical core.
It                      boots next and is given  SW-ID of 225.
Core with BSP HW ID 226 boots next and is given  SW-ID of 226.
Core with BSP HW ID 227 boots next and is given  SW-ID of 227.
*/
static ihk_spinlock_t cpuid_head_lock = 0;
static int cpuid_head = 1;

/* archtecture-depended syscall handlers */
int obtain_clone_cpuid() {
    /* see above on BSP HW ID */
	struct ihk_mc_cpu_info *cpu_info = ihk_mc_get_cpu_info();
    int cpuid, nretry = 0;
    ihk_mc_spinlock_lock_noirq(&cpuid_head_lock);
 retry:
    /* Try to obtain next physical core */
    cpuid = cpuid_head;
    cpuid_head += 4;
    if(cpuid_head >= cpu_info->ncpus) {
        cpuid_head = ((cpuid_head % 4) + 1) % 4;
    }
    /* Don't use a physical core with a system process (e.g. MPI)
       because using it degrades performance */
    if((cpu_info->ncpus - 3 <= cpuid && cpuid <= cpu_info->ncpus - 1) ||
       get_cpu_local_var(cpuid)->status != CPU_STATUS_IDLE) {
        nretry++;
        if(nretry >= cpu_info->ncpus) {
            panic("there is no cpu with empty runq\n");
        }
        goto retry; 
    }
    ihk_mc_spinlock_unlock_noirq(&cpuid_head_lock);
    return cpuid;
}