kernel/context.c

   1 /*
   2  * linux/kernel/context.c
   3  *
   4  * Mechanism for running arbitrary tasks in process context
   5  *
   6  * dwmw2@redhat.com
   7  */
   8
   9 #define __KERNEL_SYSCALLS__
  10
  11 #include <linux/module.h>
  12 #include <linux/kernel.h>
  13 #include <linux/sched.h>
  14 #include <linux/init.h>
  15 #include <linux/unistd.h>
  16 #include <linux/signal.h>
  17
  18 static DECLARE_TASK_QUEUE(tq_context);
  19 static DECLARE_WAIT_QUEUE_HEAD(context_task_wq);
  20 static int keventd_running;
  21
  22 void schedule_task(struct tq_struct *task)
  23 {
  24         if (keventd_running == 0)
  25                 printk(KERN_ERR "schedule_task(): keventd has not started\n");
  26         queue_task(task, &tq_context);
  27         wake_up(&context_task_wq);
  28 }
  29
  30 EXPORT_SYMBOL(schedule_task);
  31
  32 static int context_thread(void *dummy)
  33 {
  34         struct task_struct *curtask = current;
  35         DECLARE_WAITQUEUE(wait, curtask);
  36         struct k_sigaction sa;
  37
  38         daemonize();
  39         strcpy(curtask->comm, "keventd");
  40         keventd_running = 1;
  41
  42         spin_lock_irq(&curtask->sigmask_lock);
  43         siginitsetinv(&curtask->blocked, sigmask(SIGCHLD));
  44         recalc_sigpending(curtask);
  45         spin_unlock_irq(&curtask->sigmask_lock);
  46
  47         /* Install a handler so SIGCLD is delivered */
  48         sa.sa.sa_handler = SIG_IGN;
  49         sa.sa.sa_flags = 0;
  50         siginitset(&sa.sa.sa_mask, sigmask(SIGCHLD));
  51         do_sigaction(SIGCHLD, &sa, (struct k_sigaction *)0);
  52
  53         for (;;) {
  54                 __set_task_state(curtask, TASK_INTERRUPTIBLE);
  55                 add_wait_queue(&context_task_wq, &wait);
  56
  57                 /*
  58                  * Careful: we depend on the wait-queue modifications
  59                  * to also act as memory barriers.
  60                  */
  61                 if (!tq_context)
  62                         schedule();
  63
  64                 remove_wait_queue(&context_task_wq, &wait);
  65                 __set_task_state(curtask, TASK_RUNNING);
  66                 run_task_queue(&tq_context);
  67                 if (signal_pending(curtask)) {
  68                         while (waitpid(-1, (unsigned int *)0, __WALL|WNOHANG) > 0)
  69                                 ;
  70                         flush_signals(curtask);
  71                         recalc_sigpending(curtask);
  72                 }
  73         }
  74 }
  75
  76 int start_context_thread(void)
  77 {
  78         kernel_thread(context_thread, NULL, CLONE_FS | CLONE_FILES | CLONE_SIGHAND);
  79         return 0;
  80 }