forked from luck/tmp_suning_uos_patched
5d8f72b55c
try_to_freeze_tasks() and cgroup_freezer rely on scheduler locks to ensure that a task doing STOPPED/TRACED -> RUNNING transition can't escape freezing. This mostly works, but ptrace_stop() does not necessarily call schedule(), it can change task->state back to RUNNING and check freezing() without any lock/barrier in between. We could add the necessary barrier, but this patch changes ptrace_stop() and do_signal_stop() to use freezable_schedule(). This fixes the race, freezer_count() and freezer_should_skip() carefully avoid the race. And this simplifies the code, try_to_freeze_tasks/update_if_frozen no longer need to use task_is_stopped_or_traced() checks with the non trivial assumptions. We can rely on the mechanism which was specially designed to mark the sleeping task as "frozen enough". v2: As Tejun pointed out, we can also change get_signal_to_deliver() and move try_to_freeze() up before 'relock' label. Signed-off-by: Oleg Nesterov <oleg@redhat.com> Signed-off-by: Tejun Heo <tj@kernel.org>
210 lines
4.3 KiB
C
210 lines
4.3 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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#include <linux/kmod.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 user_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 (!user_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))
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continue;
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if (!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 (!user_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 refrigerator.
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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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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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if (!wakeup) {
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read_lock(&tasklist_lock);
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do_each_thread(g, p) {
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if (p != current && !freezer_should_skip(p)
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&& freezing(p) && !frozen(p))
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sched_show_task(p);
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} while_each_thread(g, p);
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read_unlock(&tasklist_lock);
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}
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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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* On success, returns 0. On failure, -errno and system is fully thawed.
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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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error = __usermodehelper_disable(UMH_FREEZING);
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if (error)
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return error;
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if (!pm_freezing)
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atomic_inc(&system_freezing_cnt);
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printk("Freezing user space processes ... ");
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pm_freezing = true;
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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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__usermodehelper_set_disable_depth(UMH_DISABLED);
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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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if (error)
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thaw_processes();
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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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* On success, returns 0. On failure, -errno and only the kernel threads are
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* thawed, so as to give a chance to the caller to do additional cleanups
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* (if any) before thawing the userspace tasks. So, it is the responsibility
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* of the caller to thaw the userspace tasks, when the time is right.
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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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pm_nosig_freezing = true;
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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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if (error)
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thaw_kernel_threads();
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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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if (pm_freezing)
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atomic_dec(&system_freezing_cnt);
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pm_freezing = false;
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pm_nosig_freezing = false;
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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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__thaw_task(p);
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} while_each_thread(g, p);
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read_unlock(&tasklist_lock);
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usermodehelper_enable();
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schedule();
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printk("done.\n");
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}
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void thaw_kernel_threads(void)
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{
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struct task_struct *g, *p;
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pm_nosig_freezing = false;
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printk("Restarting kernel threads ... ");
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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 (p->flags & (PF_KTHREAD | PF_WQ_WORKER))
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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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