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#include <linux/kmod.h>
20
21/*
22 * Timeout for stopping processes
23 */
24#define TIMEOUT (20 * HZ)
25
26static int try_to_freeze_tasks(bool user_only)
27{
28    struct task_struct *g, *p;
29    unsigned long end_time;
30    unsigned int todo;
31    bool wq_busy = false;
32    struct timeval start, end;
33    u64 elapsed_csecs64;
34    unsigned int elapsed_csecs;
35    bool wakeup = false;
36
37    do_gettimeofday(&start);
38
39    end_time = jiffies + TIMEOUT;
40
41    if (!user_only)
42        freeze_workqueues_begin();
43
44    while (true) {
45        todo = 0;
46        read_lock(&tasklist_lock);
47        do_each_thread(g, p) {
48            if (p == current || !freeze_task(p))
49                continue;
50
51            /*
52             * Now that we've done set_freeze_flag, don't
53             * perturb a task in TASK_STOPPED or TASK_TRACED.
54             * It is "frozen enough". If the task does wake
55             * up, it will immediately call try_to_freeze.
56             *
57             * Because freeze_task() goes through p's scheduler lock, it's
58             * guaranteed that TASK_STOPPED/TRACED -> TASK_RUNNING
59             * transition can't race with task state testing here.
60             */
61            if (!task_is_stopped_or_traced(p) &&
62                !freezer_should_skip(p))
63                todo++;
64        } while_each_thread(g, p);
65        read_unlock(&tasklist_lock);
66
67        if (!user_only) {
68            wq_busy = freeze_workqueues_busy();
69            todo += wq_busy;
70        }
71
72        if (!todo || time_after(jiffies, end_time))
73            break;
74
75        if (pm_wakeup_pending()) {
76            wakeup = true;
77            break;
78        }
79
80        /*
81         * We need to retry, but first give the freezing tasks some
82         * time to enter the regrigerator.
83         */
84        msleep(10);
85    }
86
87    do_gettimeofday(&end);
88    elapsed_csecs64 = timeval_to_ns(&end) - timeval_to_ns(&start);
89    do_div(elapsed_csecs64, NSEC_PER_SEC / 100);
90    elapsed_csecs = elapsed_csecs64;
91
92    if (todo) {
93        printk("\n");
94        printk(KERN_ERR "Freezing of tasks %s after %d.%02d seconds "
95               "(%d tasks refusing to freeze, wq_busy=%d):\n",
96               wakeup ? "aborted" : "failed",
97               elapsed_csecs / 100, elapsed_csecs % 100,
98               todo - wq_busy, wq_busy);
99
100        if (!wakeup) {
101            read_lock(&tasklist_lock);
102            do_each_thread(g, p) {
103                if (p != current && !freezer_should_skip(p)
104                    && freezing(p) && !frozen(p))
105                    sched_show_task(p);
106            } while_each_thread(g, p);
107            read_unlock(&tasklist_lock);
108        }
109    } else {
110        printk("(elapsed %d.%02d seconds) ", elapsed_csecs / 100,
111            elapsed_csecs % 100);
112    }
113
114    return todo ? -EBUSY : 0;
115}
116
117/**
118 * freeze_processes - Signal user space processes to enter the refrigerator.
119 *
120 * On success, returns 0. On failure, -errno and system is fully thawed.
121 */
122int freeze_processes(void)
123{
124    int error;
125
126    error = __usermodehelper_disable(UMH_FREEZING);
127    if (error)
128        return error;
129
130    if (!pm_freezing)
131        atomic_inc(&system_freezing_cnt);
132
133    printk("Freezing user space processes ... ");
134    pm_freezing = true;
135    error = try_to_freeze_tasks(true);
136    if (!error) {
137        printk("done.");
138        __usermodehelper_set_disable_depth(UMH_DISABLED);
139        oom_killer_disable();
140    }
141    printk("\n");
142    BUG_ON(in_atomic());
143
144    if (error)
145        thaw_processes();
146    return error;
147}
148
149/**
150 * freeze_kernel_threads - Make freezable kernel threads go to the refrigerator.
151 *
152 * On success, returns 0. On failure, -errno and only the kernel threads are
153 * thawed, so as to give a chance to the caller to do additional cleanups
154 * (if any) before thawing the userspace tasks. So, it is the responsibility
155 * of the caller to thaw the userspace tasks, when the time is right.
156 */
157int freeze_kernel_threads(void)
158{
159    int error;
160
161    printk("Freezing remaining freezable tasks ... ");
162    pm_nosig_freezing = true;
163    error = try_to_freeze_tasks(false);
164    if (!error)
165        printk("done.");
166
167    printk("\n");
168    BUG_ON(in_atomic());
169
170    if (error)
171        thaw_kernel_threads();
172    return error;
173}
174
175void thaw_processes(void)
176{
177    struct task_struct *g, *p;
178
179    if (pm_freezing)
180        atomic_dec(&system_freezing_cnt);
181    pm_freezing = false;
182    pm_nosig_freezing = false;
183
184    oom_killer_enable();
185
186    printk("Restarting tasks ... ");
187
188    thaw_workqueues();
189
190    read_lock(&tasklist_lock);
191    do_each_thread(g, p) {
192        __thaw_task(p);
193    } while_each_thread(g, p);
194    read_unlock(&tasklist_lock);
195
196    usermodehelper_enable();
197
198    schedule();
199    printk("done.\n");
200}
201
202void thaw_kernel_threads(void)
203{
204    struct task_struct *g, *p;
205
206    pm_nosig_freezing = false;
207    printk("Restarting kernel threads ... ");
208
209    thaw_workqueues();
210
211    read_lock(&tasklist_lock);
212    do_each_thread(g, p) {
213        if (p->flags & (PF_KTHREAD | PF_WQ_WORKER))
214            __thaw_task(p);
215    } while_each_thread(g, p);
216    read_unlock(&tasklist_lock);
217
218    schedule();
219    printk("done.\n");
220}
221

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