Linux SMP System Learning notes __linux

One, one CPU runs the specified function on another CPU

int smp_call_function_single (int cpu, smp_call_func_t func, void *info, int wait) Smp_call_function_single () function,
 
                Run a function on a guided CPU.
                                                else {if ((unsigned) CPU < Nr_cpu_ids && Cpu_online (CPU)) {                             struct Call_single_data *CSD = &d;
                                                                Each CPU in the system has a struct call_single_data structure if (!wait)
 
                                                CSD = &__get_cpu_var (csd_data);
 
                                                Csd_lock (CSD);
                                                Csd->func = func;
                                                Csd->info = info;   Generic_exec_single (CPU, CSD, wait);
                                                Hang to the per-CPU queue Call_single_queue and send IPI interrupts to the specified CPU else { Err =-Enxio; /* CPU not online */} void Generic_exec_single (int cpu, struct call_s Ingle_data *CSD, int wait) {//find each CPU variable call_single_queue queue struct Call_single_queue *dst = &per_c for the CPU to run the Func
    PU (call_single_queue, CPU);
    unsigned long flags;
   
    int IPI;
    Raw_spin_lock_irqsave (&dst->lock, flags); IPI = List_empty (&dst->list);//if empty return 1//hook the CSD structure to the tail call_single_queue queue of each CPU variable List_add_tail (&
    Csd->list, &dst->list);
   
    Raw_spin_unlock_irqrestore (&dst->lock, flags); If the queue is empty, it sends a IPI interrupt to the CPU to read its CSD structure on the call_single_queue of each CPU queue, thereby executing the Func function if (IPI) arch_send_call_function_single_i
   
    Pi (CPU);
If the wait sign is set, wait for the IF (waiting) csd_lock_wait (CSD); static void csd_lock_wait (struct call_single_data *CSD) {//If the CSD flag is set to a csd_flag_lock bit, wait here to loop.
The flag while (Csd->flags & Csd_flag_lock) Cpu_relax () is not set at the front; }