Merge branch 'linux-next' of git://git.infradead.org/~dedekind/ubi-2.6
[linux-2.6] / 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/suspend.h>
13 #include <linux/module.h>
14 #include <linux/syscalls.h>
15 #include <linux/freezer.h>
16
17 /* 
18  * Timeout for stopping processes
19  */
20 #define TIMEOUT (20 * HZ)
21
22 static inline int freezeable(struct task_struct * p)
23 {
24         if ((p == current) ||
25             (p->flags & PF_NOFREEZE) ||
26             (p->exit_state != 0))
27                 return 0;
28         return 1;
29 }
30
31 /*
32  * freezing is complete, mark current process as frozen
33  */
34 static inline void frozen_process(void)
35 {
36         if (!unlikely(current->flags & PF_NOFREEZE)) {
37                 current->flags |= PF_FROZEN;
38                 wmb();
39         }
40         clear_freeze_flag(current);
41 }
42
43 /* Refrigerator is place where frozen processes are stored :-). */
44 void refrigerator(void)
45 {
46         /* Hmm, should we be allowed to suspend when there are realtime
47            processes around? */
48         long save;
49
50         task_lock(current);
51         if (freezing(current)) {
52                 frozen_process();
53                 task_unlock(current);
54         } else {
55                 task_unlock(current);
56                 return;
57         }
58         save = current->state;
59         pr_debug("%s entered refrigerator\n", current->comm);
60
61         spin_lock_irq(&current->sighand->siglock);
62         recalc_sigpending(); /* We sent fake signal, clean it up */
63         spin_unlock_irq(&current->sighand->siglock);
64
65         for (;;) {
66                 set_current_state(TASK_UNINTERRUPTIBLE);
67                 if (!frozen(current))
68                         break;
69                 schedule();
70         }
71         pr_debug("%s left refrigerator\n", current->comm);
72         __set_current_state(save);
73 }
74
75 static void fake_signal_wake_up(struct task_struct *p)
76 {
77         unsigned long flags;
78
79         spin_lock_irqsave(&p->sighand->siglock, flags);
80         signal_wake_up(p, 0);
81         spin_unlock_irqrestore(&p->sighand->siglock, flags);
82 }
83
84 static inline bool should_send_signal(struct task_struct *p)
85 {
86         return !(p->flags & PF_FREEZER_NOSIG);
87 }
88
89 /**
90  *      freeze_task - send a freeze request to given task
91  *      @p: task to send the request to
92  *      @sig_only: if set, the request will only be sent if the task has the
93  *              PF_FREEZER_NOSIG flag unset
94  *      Return value: 'false', if @sig_only is set and the task has
95  *              PF_FREEZER_NOSIG set or the task is frozen, 'true', otherwise
96  *
97  *      The freeze request is sent by setting the tasks's TIF_FREEZE flag and
98  *      either sending a fake signal to it or waking it up, depending on whether
99  *      or not it has PF_FREEZER_NOSIG set.  If @sig_only is set and the task
100  *      has PF_FREEZER_NOSIG set (ie. it is a typical kernel thread), its
101  *      TIF_FREEZE flag will not be set.
102  */
103 static bool freeze_task(struct task_struct *p, bool sig_only)
104 {
105         /*
106          * We first check if the task is freezing and next if it has already
107          * been frozen to avoid the race with frozen_process() which first marks
108          * the task as frozen and next clears its TIF_FREEZE.
109          */
110         if (!freezing(p)) {
111                 rmb();
112                 if (frozen(p))
113                         return false;
114
115                 if (!sig_only || should_send_signal(p))
116                         set_freeze_flag(p);
117                 else
118                         return false;
119         }
120
121         if (should_send_signal(p)) {
122                 if (!signal_pending(p))
123                         fake_signal_wake_up(p);
124         } else if (sig_only) {
125                 return false;
126         } else {
127                 wake_up_state(p, TASK_INTERRUPTIBLE);
128         }
129
130         return true;
131 }
132
133 static void cancel_freezing(struct task_struct *p)
134 {
135         unsigned long flags;
136
137         if (freezing(p)) {
138                 pr_debug("  clean up: %s\n", p->comm);
139                 clear_freeze_flag(p);
140                 spin_lock_irqsave(&p->sighand->siglock, flags);
141                 recalc_sigpending_and_wake(p);
142                 spin_unlock_irqrestore(&p->sighand->siglock, flags);
143         }
144 }
145
146 static int try_to_freeze_tasks(bool sig_only)
147 {
148         struct task_struct *g, *p;
149         unsigned long end_time;
150         unsigned int todo;
151         struct timeval start, end;
152         s64 elapsed_csecs64;
153         unsigned int elapsed_csecs;
154
155         do_gettimeofday(&start);
156
157         end_time = jiffies + TIMEOUT;
158         do {
159                 todo = 0;
160                 read_lock(&tasklist_lock);
161                 do_each_thread(g, p) {
162                         if (frozen(p) || !freezeable(p))
163                                 continue;
164
165                         if (!freeze_task(p, sig_only))
166                                 continue;
167
168                         /*
169                          * Now that we've done set_freeze_flag, don't
170                          * perturb a task in TASK_STOPPED or TASK_TRACED.
171                          * It is "frozen enough".  If the task does wake
172                          * up, it will immediately call try_to_freeze.
173                          */
174                         if (!task_is_stopped_or_traced(p) &&
175                             !freezer_should_skip(p))
176                                 todo++;
177                 } while_each_thread(g, p);
178                 read_unlock(&tasklist_lock);
179                 yield();                        /* Yield is okay here */
180                 if (time_after(jiffies, end_time))
181                         break;
182         } while (todo);
183
184         do_gettimeofday(&end);
185         elapsed_csecs64 = timeval_to_ns(&end) - timeval_to_ns(&start);
186         do_div(elapsed_csecs64, NSEC_PER_SEC / 100);
187         elapsed_csecs = elapsed_csecs64;
188
189         if (todo) {
190                 /* This does not unfreeze processes that are already frozen
191                  * (we have slightly ugly calling convention in that respect,
192                  * and caller must call thaw_processes() if something fails),
193                  * but it cleans up leftover PF_FREEZE requests.
194                  */
195                 printk("\n");
196                 printk(KERN_ERR "Freezing of tasks failed after %d.%02d seconds "
197                                 "(%d tasks refusing to freeze):\n",
198                                 elapsed_csecs / 100, elapsed_csecs % 100, todo);
199                 show_state();
200                 read_lock(&tasklist_lock);
201                 do_each_thread(g, p) {
202                         task_lock(p);
203                         if (freezing(p) && !freezer_should_skip(p))
204                                 printk(KERN_ERR " %s\n", p->comm);
205                         cancel_freezing(p);
206                         task_unlock(p);
207                 } while_each_thread(g, p);
208                 read_unlock(&tasklist_lock);
209         } else {
210                 printk("(elapsed %d.%02d seconds) ", elapsed_csecs / 100,
211                         elapsed_csecs % 100);
212         }
213
214         return todo ? -EBUSY : 0;
215 }
216
217 /**
218  *      freeze_processes - tell processes to enter the refrigerator
219  */
220 int freeze_processes(void)
221 {
222         int error;
223
224         printk("Freezing user space processes ... ");
225         error = try_to_freeze_tasks(true);
226         if (error)
227                 goto Exit;
228         printk("done.\n");
229
230         printk("Freezing remaining freezable tasks ... ");
231         error = try_to_freeze_tasks(false);
232         if (error)
233                 goto Exit;
234         printk("done.");
235  Exit:
236         BUG_ON(in_atomic());
237         printk("\n");
238         return error;
239 }
240
241 static void thaw_tasks(bool nosig_only)
242 {
243         struct task_struct *g, *p;
244
245         read_lock(&tasklist_lock);
246         do_each_thread(g, p) {
247                 if (!freezeable(p))
248                         continue;
249
250                 if (nosig_only && should_send_signal(p))
251                         continue;
252
253                 thaw_process(p);
254         } while_each_thread(g, p);
255         read_unlock(&tasklist_lock);
256 }
257
258 void thaw_processes(void)
259 {
260         printk("Restarting tasks ... ");
261         thaw_tasks(true);
262         thaw_tasks(false);
263         schedule();
264         printk("done.\n");
265 }
266
267 EXPORT_SYMBOL(refrigerator);