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/*
* linux/kernel/context.c
*
* Mechanism for running arbitrary tasks in process context
*
* dwmw2@redhat.com: Genesis
*
* andrewm@uow.edu.au: 2.4.0-test12
* - Child reaping
* - Support for tasks which re-add themselves
* - flush_scheduled_tasks.
*/
#define __KERNEL_SYSCALLS__
#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/sched.h>
#include <linux/init.h>
#include <linux/unistd.h>
#include <linux/signal.h>
static DECLARE_TASK_QUEUE(tq_context);
static DECLARE_WAIT_QUEUE_HEAD(context_task_wq);
static DECLARE_WAIT_QUEUE_HEAD(context_task_done);
static int keventd_running;
static struct task_struct *keventd_task;
static int need_keventd(const char *who)
{
if (keventd_running == 0)
printk(KERN_ERR "%s(): keventd has not started\n", who);
return keventd_running;
}
int current_is_keventd(void)
{
int ret = 0;
if (need_keventd(__FUNCTION__))
ret = (current == keventd_task);
return ret;
}
/**
* schedule_task - schedule a function for subsequent execution in process context.
* @task: pointer to a &tq_struct which defines the function to be scheduled.
*
* May be called from interrupt context. The scheduled function is run at some
* time in the near future by the keventd kernel thread. If it can sleep, it
* should be designed to do so for the minimum possible time, as it will be
* stalling all other scheduled tasks.
*
* schedule_task() returns non-zero if the task was successfully scheduled.
* If @task is already residing on a task queue then schedule_task() fails
* to schedule your task and returns zero.
*/
int schedule_task(struct tq_struct *task)
{
int ret;
need_keventd(__FUNCTION__);
ret = queue_task(task, &tq_context);
wake_up(&context_task_wq);
return ret;
}
static int context_thread(void *dummy)
{
struct task_struct *curtask = current;
DECLARE_WAITQUEUE(wait, curtask);
struct k_sigaction sa;
daemonize();
strcpy(curtask->comm, "keventd");
keventd_running = 1;
keventd_task = curtask;
spin_lock_irq(&curtask->sigmask_lock);
siginitsetinv(&curtask->blocked, sigmask(SIGCHLD));
recalc_sigpending(curtask);
spin_unlock_irq(&curtask->sigmask_lock);
/* Install a handler so SIGCLD is delivered */
sa.sa.sa_handler = SIG_IGN;
sa.sa.sa_flags = 0;
siginitset(&sa.sa.sa_mask, sigmask(SIGCHLD));
do_sigaction(SIGCHLD, &sa, (struct k_sigaction *)0);
/*
* If one of the functions on a task queue re-adds itself
* to the task queue we call schedule() in state TASK_RUNNING
*/
for (;;) {
set_task_state(curtask, TASK_INTERRUPTIBLE);
add_wait_queue(&context_task_wq, &wait);
if (TQ_ACTIVE(tq_context))
set_task_state(curtask, TASK_RUNNING);
schedule();
remove_wait_queue(&context_task_wq, &wait);
run_task_queue(&tq_context);
wake_up(&context_task_done);
if (signal_pending(curtask)) {
while (waitpid(-1, (unsigned int *)0, __WALL|WNOHANG) > 0)
;
flush_signals(curtask);
recalc_sigpending(curtask);
}
}
}
/**
* flush_scheduled_tasks - ensure that any scheduled tasks have run to completion.
*
* Forces execution of the schedule_task() queue and blocks until its completion.
*
* If a kernel subsystem uses schedule_task() and wishes to flush any pending
* tasks, it should use this function. This is typically used in driver shutdown
* handlers.
*
* The caller should hold no spinlocks and should hold no semaphores which could
* cause the scheduled tasks to block.
*/
static struct tq_struct dummy_task;
void flush_scheduled_tasks(void)
{
int count;
DECLARE_WAITQUEUE(wait, current);
/*
* Do it twice. It's possible, albeit highly unlikely, that
* the caller queued a task immediately before calling us,
* and that the eventd thread was already past the run_task_queue()
* but not yet into wake_up(), so it woke us up before completing
* the caller's queued task or our new dummy task.
*/
add_wait_queue(&context_task_done, &wait);
for (count = 0; count < 2; count++) {
set_current_state(TASK_UNINTERRUPTIBLE);
/* Queue a dummy task to make sure we get kicked */
schedule_task(&dummy_task);
/* Wait for it to complete */
schedule();
}
remove_wait_queue(&context_task_done, &wait);
}
int start_context_thread(void)
{
kernel_thread(context_thread, NULL, CLONE_FS | CLONE_FILES);
return 0;
}
EXPORT_SYMBOL(schedule_task);
EXPORT_SYMBOL(flush_scheduled_tasks);
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