Root/kernel/power/process.c

1/*
2 * drivers/power/process.c - Functions for starting/stopping processes on
3 * suspend transitions.
4 *
5 * Originally from swsusp.
6 */
7
8
9#undef DEBUG
10
11#include <linux/interrupt.h>
12#include <linux/oom.h>
13#include <linux/suspend.h>
14#include <linux/module.h>
15#include <linux/syscalls.h>
16#include <linux/freezer.h>
17#include <linux/delay.h>
18#include <linux/workqueue.h>
19
20/*
21 * Timeout for stopping processes
22 */
23#define TIMEOUT (20 * HZ)
24
25static inline int freezable(struct task_struct * p)
26{
27    if ((p == current) ||
28        (p->flags & PF_NOFREEZE) ||
29        (p->exit_state != 0))
30        return 0;
31    return 1;
32}
33
34static int try_to_freeze_tasks(bool sig_only)
35{
36    struct task_struct *g, *p;
37    unsigned long end_time;
38    unsigned int todo;
39    bool wq_busy = false;
40    struct timeval start, end;
41    u64 elapsed_csecs64;
42    unsigned int elapsed_csecs;
43    bool wakeup = false;
44
45    do_gettimeofday(&start);
46
47    end_time = jiffies + TIMEOUT;
48
49    if (!sig_only)
50        freeze_workqueues_begin();
51
52    while (true) {
53        todo = 0;
54        read_lock(&tasklist_lock);
55        do_each_thread(g, p) {
56            if (frozen(p) || !freezable(p))
57                continue;
58
59            if (!freeze_task(p, sig_only))
60                continue;
61
62            /*
63             * Now that we've done set_freeze_flag, don't
64             * perturb a task in TASK_STOPPED or TASK_TRACED.
65             * It is "frozen enough". If the task does wake
66             * up, it will immediately call try_to_freeze.
67             *
68             * Because freeze_task() goes through p's
69             * scheduler lock after setting TIF_FREEZE, it's
70             * guaranteed that either we see TASK_RUNNING or
71             * try_to_stop() after schedule() in ptrace/signal
72             * stop sees TIF_FREEZE.
73             */
74            if (!task_is_stopped_or_traced(p) &&
75                !freezer_should_skip(p))
76                todo++;
77        } while_each_thread(g, p);
78        read_unlock(&tasklist_lock);
79
80        if (!sig_only) {
81            wq_busy = freeze_workqueues_busy();
82            todo += wq_busy;
83        }
84
85        if (!todo || time_after(jiffies, end_time))
86            break;
87
88        if (pm_wakeup_pending()) {
89            wakeup = true;
90            break;
91        }
92
93        /*
94         * We need to retry, but first give the freezing tasks some
95         * time to enter the regrigerator.
96         */
97        msleep(10);
98    }
99
100    do_gettimeofday(&end);
101    elapsed_csecs64 = timeval_to_ns(&end) - timeval_to_ns(&start);
102    do_div(elapsed_csecs64, NSEC_PER_SEC / 100);
103    elapsed_csecs = elapsed_csecs64;
104
105    if (todo) {
106        /* This does not unfreeze processes that are already frozen
107         * (we have slightly ugly calling convention in that respect,
108         * and caller must call thaw_processes() if something fails),
109         * but it cleans up leftover PF_FREEZE requests.
110         */
111        printk("\n");
112        printk(KERN_ERR "Freezing of tasks %s after %d.%02d seconds "
113               "(%d tasks refusing to freeze, wq_busy=%d):\n",
114               wakeup ? "aborted" : "failed",
115               elapsed_csecs / 100, elapsed_csecs % 100,
116               todo - wq_busy, wq_busy);
117
118        thaw_workqueues();
119
120        read_lock(&tasklist_lock);
121        do_each_thread(g, p) {
122            task_lock(p);
123            if (!wakeup && freezing(p) && !freezer_should_skip(p))
124                sched_show_task(p);
125            cancel_freezing(p);
126            task_unlock(p);
127        } while_each_thread(g, p);
128        read_unlock(&tasklist_lock);
129    } else {
130        printk("(elapsed %d.%02d seconds) ", elapsed_csecs / 100,
131            elapsed_csecs % 100);
132    }
133
134    return todo ? -EBUSY : 0;
135}
136
137/**
138 * freeze_processes - tell processes to enter the refrigerator
139 */
140int freeze_processes(void)
141{
142    int error;
143
144    printk("Freezing user space processes ... ");
145    error = try_to_freeze_tasks(true);
146    if (error)
147        goto Exit;
148    printk("done.\n");
149
150    printk("Freezing remaining freezable tasks ... ");
151    error = try_to_freeze_tasks(false);
152    if (error)
153        goto Exit;
154    printk("done.");
155
156    oom_killer_disable();
157 Exit:
158    BUG_ON(in_atomic());
159    printk("\n");
160
161    return error;
162}
163
164static void thaw_tasks(bool nosig_only)
165{
166    struct task_struct *g, *p;
167
168    read_lock(&tasklist_lock);
169    do_each_thread(g, p) {
170        if (!freezable(p))
171            continue;
172
173        if (nosig_only && should_send_signal(p))
174            continue;
175
176        if (cgroup_freezing_or_frozen(p))
177            continue;
178
179        thaw_process(p);
180    } while_each_thread(g, p);
181    read_unlock(&tasklist_lock);
182}
183
184void thaw_processes(void)
185{
186    oom_killer_enable();
187
188    printk("Restarting tasks ... ");
189    thaw_workqueues();
190    thaw_tasks(true);
191    thaw_tasks(false);
192    schedule();
193    printk("done.\n");
194}
195
196

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