1 // SPDX-License-Identifier: GPL-2.0 2 /* 3 * drivers/power/process.c - Functions for starting/stopping processes on 4 * suspend transitions. 5 * 6 * Originally from swsusp. 7 */ 8 9 10 #undef DEBUG 11 12 #include <linux/interrupt.h> 13 #include <linux/oom.h> 14 #include <linux/suspend.h> 15 #include <linux/module.h> 16 #include <linux/sched/debug.h> 17 #include <linux/sched/task.h> 18 #include <linux/syscalls.h> 19 #include <linux/freezer.h> 20 #include <linux/delay.h> 21 #include <linux/workqueue.h> 22 #include <linux/kmod.h> 23 #include <trace/events/power.h> 24 #include <linux/cpuset.h> 25 26 /* 27 * Timeout for stopping processes 28 */ 29 unsigned int __read_mostly freeze_timeout_msecs = 20 * MSEC_PER_SEC; 30 31 static int try_to_freeze_tasks(bool user_only) 32 { 33 struct task_struct *g, *p; 34 unsigned long end_time; 35 unsigned int todo; 36 bool wq_busy = false; 37 ktime_t start, end, elapsed; 38 unsigned int elapsed_msecs; 39 bool wakeup = false; 40 int sleep_usecs = USEC_PER_MSEC; 41 42 start = ktime_get_boottime(); 43 44 end_time = jiffies + msecs_to_jiffies(freeze_timeout_msecs); 45 46 if (!user_only) 47 freeze_workqueues_begin(); 48 49 while (true) { 50 todo = 0; 51 read_lock(&tasklist_lock); 52 for_each_process_thread(g, p) { 53 if (p == current || !freeze_task(p)) 54 continue; 55 56 if (!freezer_should_skip(p)) 57 todo++; 58 } 59 read_unlock(&tasklist_lock); 60 61 if (!user_only) { 62 wq_busy = freeze_workqueues_busy(); 63 todo += wq_busy; 64 } 65 66 if (!todo || time_after(jiffies, end_time)) 67 break; 68 69 if (pm_wakeup_pending()) { 70 wakeup = true; 71 break; 72 } 73 74 /* 75 * We need to retry, but first give the freezing tasks some 76 * time to enter the refrigerator. Start with an initial 77 * 1 ms sleep followed by exponential backoff until 8 ms. 78 */ 79 usleep_range(sleep_usecs / 2, sleep_usecs); 80 if (sleep_usecs < 8 * USEC_PER_MSEC) 81 sleep_usecs *= 2; 82 } 83 84 end = ktime_get_boottime(); 85 elapsed = ktime_sub(end, start); 86 elapsed_msecs = ktime_to_ms(elapsed); 87 88 if (todo) { 89 pr_cont("\n"); 90 pr_err("Freezing of tasks %s after %d.%03d seconds " 91 "(%d tasks refusing to freeze, wq_busy=%d):\n", 92 wakeup ? "aborted" : "failed", 93 elapsed_msecs / 1000, elapsed_msecs % 1000, 94 todo - wq_busy, wq_busy); 95 96 if (wq_busy) 97 show_all_workqueues(); 98 99 if (!wakeup || pm_debug_messages_on) { 100 read_lock(&tasklist_lock); 101 for_each_process_thread(g, p) { 102 if (p != current && !freezer_should_skip(p) 103 && freezing(p) && !frozen(p)) 104 sched_show_task(p); 105 } 106 read_unlock(&tasklist_lock); 107 } 108 } else { 109 pr_cont("(elapsed %d.%03d seconds) ", elapsed_msecs / 1000, 110 elapsed_msecs % 1000); 111 } 112 113 return todo ? -EBUSY : 0; 114 } 115 116 /** 117 * freeze_processes - Signal user space processes to enter the refrigerator. 118 * The current thread will not be frozen. The same process that calls 119 * freeze_processes must later call thaw_processes. 120 * 121 * On success, returns 0. On failure, -errno and system is fully thawed. 122 */ 123 int freeze_processes(void) 124 { 125 int error; 126 127 error = __usermodehelper_disable(UMH_FREEZING); 128 if (error) 129 return error; 130 131 /* Make sure this task doesn't get frozen */ 132 current->flags |= PF_SUSPEND_TASK; 133 134 if (!pm_freezing) 135 atomic_inc(&system_freezing_cnt); 136 137 pm_wakeup_clear(0); 138 pr_info("Freezing user space processes ... "); 139 pm_freezing = true; 140 error = try_to_freeze_tasks(true); 141 if (!error) { 142 __usermodehelper_set_disable_depth(UMH_DISABLED); 143 pr_cont("done."); 144 } 145 pr_cont("\n"); 146 BUG_ON(in_atomic()); 147 148 /* 149 * Now that the whole userspace is frozen we need to disable 150 * the OOM killer to disallow any further interference with 151 * killable tasks. There is no guarantee oom victims will 152 * ever reach a point they go away we have to wait with a timeout. 153 */ 154 if (!error && !oom_killer_disable(msecs_to_jiffies(freeze_timeout_msecs))) 155 error = -EBUSY; 156 157 if (error) 158 thaw_processes(); 159 return error; 160 } 161 162 /** 163 * freeze_kernel_threads - Make freezable kernel threads go to the refrigerator. 164 * 165 * On success, returns 0. On failure, -errno and only the kernel threads are 166 * thawed, so as to give a chance to the caller to do additional cleanups 167 * (if any) before thawing the userspace tasks. So, it is the responsibility 168 * of the caller to thaw the userspace tasks, when the time is right. 169 */ 170 int freeze_kernel_threads(void) 171 { 172 int error; 173 174 pr_info("Freezing remaining freezable tasks ... "); 175 176 pm_nosig_freezing = true; 177 error = try_to_freeze_tasks(false); 178 if (!error) 179 pr_cont("done."); 180 181 pr_cont("\n"); 182 BUG_ON(in_atomic()); 183 184 if (error) 185 thaw_kernel_threads(); 186 return error; 187 } 188 189 void thaw_processes(void) 190 { 191 struct task_struct *g, *p; 192 struct task_struct *curr = current; 193 194 trace_suspend_resume(TPS("thaw_processes"), 0, true); 195 if (pm_freezing) 196 atomic_dec(&system_freezing_cnt); 197 pm_freezing = false; 198 pm_nosig_freezing = false; 199 200 oom_killer_enable(); 201 202 pr_info("Restarting tasks ... "); 203 204 __usermodehelper_set_disable_depth(UMH_FREEZING); 205 thaw_workqueues(); 206 207 cpuset_wait_for_hotplug(); 208 209 read_lock(&tasklist_lock); 210 for_each_process_thread(g, p) { 211 /* No other threads should have PF_SUSPEND_TASK set */ 212 WARN_ON((p != curr) && (p->flags & PF_SUSPEND_TASK)); 213 __thaw_task(p); 214 } 215 read_unlock(&tasklist_lock); 216 217 WARN_ON(!(curr->flags & PF_SUSPEND_TASK)); 218 curr->flags &= ~PF_SUSPEND_TASK; 219 220 usermodehelper_enable(); 221 222 schedule(); 223 pr_cont("done.\n"); 224 trace_suspend_resume(TPS("thaw_processes"), 0, false); 225 } 226 227 void thaw_kernel_threads(void) 228 { 229 struct task_struct *g, *p; 230 231 pm_nosig_freezing = false; 232 pr_info("Restarting kernel threads ... "); 233 234 thaw_workqueues(); 235 236 read_lock(&tasklist_lock); 237 for_each_process_thread(g, p) { 238 if (p->flags & PF_KTHREAD) 239 __thaw_task(p); 240 } 241 read_unlock(&tasklist_lock); 242 243 schedule(); 244 pr_cont("done.\n"); 245 } 246