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![Tejun Heo](/assets/img/avatar_default.png)
try_to_freeze_tasks() and thaw_processes() use freezable() and frozen() as preliminary tests before initiating operations on a task. These are done without any synchronization and hinder with synchronization cleanup without any real performance benefits. In try_to_freeze_tasks(), open code self test and move PF_NOFREEZE and frozen() tests inside freezer_lock in freeze_task(). thaw_processes() can simply drop freezable() test as frozen() test in __thaw_task() is enough. Note: This used to be a part of larger patch to fix set_freezable() race. Separated out to satisfy ordering among dependent fixes. Signed-off-by: Tejun Heo <tj@kernel.org> Cc: Oleg Nesterov <oleg@redhat.com>
183 lines
3.9 KiB
C
183 lines
3.9 KiB
C
/*
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* drivers/power/process.c - Functions for starting/stopping processes on
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* suspend transitions.
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*
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* Originally from swsusp.
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*/
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#undef DEBUG
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#include <linux/interrupt.h>
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#include <linux/oom.h>
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#include <linux/suspend.h>
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#include <linux/module.h>
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#include <linux/syscalls.h>
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#include <linux/freezer.h>
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#include <linux/delay.h>
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#include <linux/workqueue.h>
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/*
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* Timeout for stopping processes
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*/
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#define TIMEOUT (20 * HZ)
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static int try_to_freeze_tasks(bool sig_only)
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{
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struct task_struct *g, *p;
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unsigned long end_time;
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unsigned int todo;
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bool wq_busy = false;
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struct timeval start, end;
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u64 elapsed_csecs64;
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unsigned int elapsed_csecs;
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bool wakeup = false;
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do_gettimeofday(&start);
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end_time = jiffies + TIMEOUT;
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if (!sig_only)
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freeze_workqueues_begin();
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while (true) {
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todo = 0;
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read_lock(&tasklist_lock);
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do_each_thread(g, p) {
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if (p == current || !freeze_task(p, sig_only))
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continue;
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/*
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* Now that we've done set_freeze_flag, don't
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* perturb a task in TASK_STOPPED or TASK_TRACED.
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* It is "frozen enough". If the task does wake
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* up, it will immediately call try_to_freeze.
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*
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* Because freeze_task() goes through p's
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* scheduler lock after setting TIF_FREEZE, it's
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* guaranteed that either we see TASK_RUNNING or
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* try_to_stop() after schedule() in ptrace/signal
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* stop sees TIF_FREEZE.
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*/
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if (!task_is_stopped_or_traced(p) &&
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!freezer_should_skip(p))
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todo++;
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} while_each_thread(g, p);
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read_unlock(&tasklist_lock);
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if (!sig_only) {
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wq_busy = freeze_workqueues_busy();
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todo += wq_busy;
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}
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if (!todo || time_after(jiffies, end_time))
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break;
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if (pm_wakeup_pending()) {
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wakeup = true;
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break;
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}
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/*
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* We need to retry, but first give the freezing tasks some
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* time to enter the regrigerator.
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*/
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msleep(10);
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}
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do_gettimeofday(&end);
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elapsed_csecs64 = timeval_to_ns(&end) - timeval_to_ns(&start);
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do_div(elapsed_csecs64, NSEC_PER_SEC / 100);
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elapsed_csecs = elapsed_csecs64;
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if (todo) {
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/* This does not unfreeze processes that are already frozen
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* (we have slightly ugly calling convention in that respect,
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* and caller must call thaw_processes() if something fails),
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* but it cleans up leftover PF_FREEZE requests.
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*/
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printk("\n");
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printk(KERN_ERR "Freezing of tasks %s after %d.%02d seconds "
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"(%d tasks refusing to freeze, wq_busy=%d):\n",
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wakeup ? "aborted" : "failed",
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elapsed_csecs / 100, elapsed_csecs % 100,
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todo - wq_busy, wq_busy);
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thaw_workqueues();
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read_lock(&tasklist_lock);
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do_each_thread(g, p) {
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if (!wakeup && !freezer_should_skip(p) &&
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freezing(p) && !frozen(p))
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sched_show_task(p);
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cancel_freezing(p);
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} while_each_thread(g, p);
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read_unlock(&tasklist_lock);
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} else {
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printk("(elapsed %d.%02d seconds) ", elapsed_csecs / 100,
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elapsed_csecs % 100);
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}
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return todo ? -EBUSY : 0;
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}
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/**
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* freeze_processes - Signal user space processes to enter the refrigerator.
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*/
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int freeze_processes(void)
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{
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int error;
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printk("Freezing user space processes ... ");
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error = try_to_freeze_tasks(true);
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if (!error) {
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printk("done.");
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oom_killer_disable();
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}
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printk("\n");
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BUG_ON(in_atomic());
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return error;
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}
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/**
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* freeze_kernel_threads - Make freezable kernel threads go to the refrigerator.
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*/
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int freeze_kernel_threads(void)
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{
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int error;
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printk("Freezing remaining freezable tasks ... ");
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error = try_to_freeze_tasks(false);
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if (!error)
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printk("done.");
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printk("\n");
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BUG_ON(in_atomic());
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return error;
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}
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void thaw_processes(void)
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{
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struct task_struct *g, *p;
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oom_killer_enable();
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printk("Restarting tasks ... ");
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thaw_workqueues();
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read_lock(&tasklist_lock);
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do_each_thread(g, p) {
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if (cgroup_freezing_or_frozen(p))
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continue;
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__thaw_task(p);
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} while_each_thread(g, p);
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read_unlock(&tasklist_lock);
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schedule();
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printk("done.\n");
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}
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