/* * drivers/power/process.c - Functions for starting/stopping processes on * suspend transitions. * * Originally from swsusp. */ #undef DEBUG #include #include #include #include #include /* * Timeout for stopping processes */ #define TIMEOUT (20 * HZ) static inline int freezeable(struct task_struct * p) { if ((p == current) || (p->flags & PF_NOFREEZE) || (p->exit_state != 0)) return 0; return 1; } /* * freezing is complete, mark current process as frozen */ static inline void frozen_process(void) { if (!unlikely(current->flags & PF_NOFREEZE)) { current->flags |= PF_FROZEN; wmb(); } clear_freeze_flag(current); } /* Refrigerator is place where frozen processes are stored :-). */ void refrigerator(void) { /* Hmm, should we be allowed to suspend when there are realtime processes around? */ long save; task_lock(current); if (freezing(current)) { frozen_process(); task_unlock(current); } else { task_unlock(current); return; } save = current->state; pr_debug("%s entered refrigerator\n", current->comm); spin_lock_irq(¤t->sighand->siglock); recalc_sigpending(); /* We sent fake signal, clean it up */ spin_unlock_irq(¤t->sighand->siglock); for (;;) { set_current_state(TASK_UNINTERRUPTIBLE); if (!frozen(current)) break; schedule(); } pr_debug("%s left refrigerator\n", current->comm); __set_current_state(save); } static void fake_signal_wake_up(struct task_struct *p) { unsigned long flags; spin_lock_irqsave(&p->sighand->siglock, flags); signal_wake_up(p, 0); spin_unlock_irqrestore(&p->sighand->siglock, flags); } static inline bool should_send_signal(struct task_struct *p) { return !(p->flags & PF_FREEZER_NOSIG); } /** * freeze_task - send a freeze request to given task * @p: task to send the request to * @sig_only: if set, the request will only be sent if the task has the * PF_FREEZER_NOSIG flag unset * Return value: 'false', if @sig_only is set and the task has * PF_FREEZER_NOSIG set or the task is frozen, 'true', otherwise * * The freeze request is sent by setting the tasks's TIF_FREEZE flag and * either sending a fake signal to it or waking it up, depending on whether * or not it has PF_FREEZER_NOSIG set. If @sig_only is set and the task * has PF_FREEZER_NOSIG set (ie. it is a typical kernel thread), its * TIF_FREEZE flag will not be set. */ static bool freeze_task(struct task_struct *p, bool sig_only) { /* * We first check if the task is freezing and next if it has already * been frozen to avoid the race with frozen_process() which first marks * the task as frozen and next clears its TIF_FREEZE. */ if (!freezing(p)) { rmb(); if (frozen(p)) return false; if (!sig_only || should_send_signal(p)) set_freeze_flag(p); else return false; } if (should_send_signal(p)) { if (!signal_pending(p)) fake_signal_wake_up(p); } else if (sig_only) { return false; } else { wake_up_state(p, TASK_INTERRUPTIBLE); } return true; } static void cancel_freezing(struct task_struct *p) { unsigned long flags; if (freezing(p)) { pr_debug(" clean up: %s\n", p->comm); clear_freeze_flag(p); spin_lock_irqsave(&p->sighand->siglock, flags); recalc_sigpending_and_wake(p); spin_unlock_irqrestore(&p->sighand->siglock, flags); } } static int try_to_freeze_tasks(bool sig_only) { struct task_struct *g, *p; unsigned long end_time; unsigned int todo; struct timeval start, end; u64 elapsed_csecs64; unsigned int elapsed_csecs; do_gettimeofday(&start); end_time = jiffies + TIMEOUT; do { todo = 0; read_lock(&tasklist_lock); do_each_thread(g, p) { if (frozen(p) || !freezeable(p)) continue; if (!freeze_task(p, sig_only)) continue; /* * Now that we've done set_freeze_flag, don't * perturb a task in TASK_STOPPED or TASK_TRACED. * It is "frozen enough". If the task does wake * up, it will immediately call try_to_freeze. */ if (!task_is_stopped_or_traced(p) && !freezer_should_skip(p)) todo++; } while_each_thread(g, p); read_unlock(&tasklist_lock); yield(); /* Yield is okay here */ if (time_after(jiffies, end_time)) break; } while (todo); do_gettimeofday(&end); elapsed_csecs64 = timeval_to_ns(&end) - timeval_to_ns(&start); do_div(elapsed_csecs64, NSEC_PER_SEC / 100); elapsed_csecs = elapsed_csecs64; if (todo) { /* This does not unfreeze processes that are already frozen * (we have slightly ugly calling convention in that respect, * and caller must call thaw_processes() if something fails), * but it cleans up leftover PF_FREEZE requests. */ printk("\n"); printk(KERN_ERR "Freezing of tasks failed after %d.%02d seconds " "(%d tasks refusing to freeze):\n", elapsed_csecs / 100, elapsed_csecs % 100, todo); show_state(); read_lock(&tasklist_lock); do_each_thread(g, p) { task_lock(p); if (freezing(p) && !freezer_should_skip(p)) printk(KERN_ERR " %s\n", p->comm); cancel_freezing(p); task_unlock(p); } while_each_thread(g, p); read_unlock(&tasklist_lock); } else { printk("(elapsed %d.%02d seconds) ", elapsed_csecs / 100, elapsed_csecs % 100); } return todo ? -EBUSY : 0; } /** * freeze_processes - tell processes to enter the refrigerator */ int freeze_processes(void) { int error; printk("Freezing user space processes ... "); error = try_to_freeze_tasks(true); if (error) goto Exit; printk("done.\n"); printk("Freezing remaining freezable tasks ... "); error = try_to_freeze_tasks(false); if (error) goto Exit; printk("done."); Exit: BUG_ON(in_atomic()); printk("\n"); return error; } static void thaw_tasks(bool nosig_only) { struct task_struct *g, *p; read_lock(&tasklist_lock); do_each_thread(g, p) { if (!freezeable(p)) continue; if (nosig_only && should_send_signal(p)) continue; thaw_process(p); } while_each_thread(g, p); read_unlock(&tasklist_lock); } void thaw_processes(void) { printk("Restarting tasks ... "); thaw_tasks(true); thaw_tasks(false); schedule(); printk("done.\n"); } EXPORT_SYMBOL(refrigerator);