mirror of
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
synced 2024-08-26 02:39:48 +00:00
![Oleg Nesterov](/assets/img/avatar_default.png)
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>
209 lines
4.3 KiB
C
209 lines
4.3 KiB
C
/*
|
|
* drivers/power/process.c - Functions for starting/stopping processes on
|
|
* suspend transitions.
|
|
*
|
|
* Originally from swsusp.
|
|
*/
|
|
|
|
|
|
#undef DEBUG
|
|
|
|
#include <linux/interrupt.h>
|
|
#include <linux/oom.h>
|
|
#include <linux/suspend.h>
|
|
#include <linux/module.h>
|
|
#include <linux/syscalls.h>
|
|
#include <linux/freezer.h>
|
|
#include <linux/delay.h>
|
|
#include <linux/workqueue.h>
|
|
#include <linux/kmod.h>
|
|
|
|
/*
|
|
* Timeout for stopping processes
|
|
*/
|
|
#define TIMEOUT (20 * HZ)
|
|
|
|
static int try_to_freeze_tasks(bool user_only)
|
|
{
|
|
struct task_struct *g, *p;
|
|
unsigned long end_time;
|
|
unsigned int todo;
|
|
bool wq_busy = false;
|
|
struct timeval start, end;
|
|
u64 elapsed_csecs64;
|
|
unsigned int elapsed_csecs;
|
|
bool wakeup = false;
|
|
|
|
do_gettimeofday(&start);
|
|
|
|
end_time = jiffies + TIMEOUT;
|
|
|
|
if (!user_only)
|
|
freeze_workqueues_begin();
|
|
|
|
while (true) {
|
|
todo = 0;
|
|
read_lock(&tasklist_lock);
|
|
do_each_thread(g, p) {
|
|
if (p == current || !freeze_task(p))
|
|
continue;
|
|
|
|
if (!freezer_should_skip(p))
|
|
todo++;
|
|
} while_each_thread(g, p);
|
|
read_unlock(&tasklist_lock);
|
|
|
|
if (!user_only) {
|
|
wq_busy = freeze_workqueues_busy();
|
|
todo += wq_busy;
|
|
}
|
|
|
|
if (!todo || time_after(jiffies, end_time))
|
|
break;
|
|
|
|
if (pm_wakeup_pending()) {
|
|
wakeup = true;
|
|
break;
|
|
}
|
|
|
|
/*
|
|
* We need to retry, but first give the freezing tasks some
|
|
* time to enter the refrigerator.
|
|
*/
|
|
msleep(10);
|
|
}
|
|
|
|
do_gettimeofday(&end);
|
|
elapsed_csecs64 = timeval_to_ns(&end) - timeval_to_ns(&start);
|
|
do_div(elapsed_csecs64, NSEC_PER_SEC / 100);
|
|
elapsed_csecs = elapsed_csecs64;
|
|
|
|
if (todo) {
|
|
printk("\n");
|
|
printk(KERN_ERR "Freezing of tasks %s after %d.%02d seconds "
|
|
"(%d tasks refusing to freeze, wq_busy=%d):\n",
|
|
wakeup ? "aborted" : "failed",
|
|
elapsed_csecs / 100, elapsed_csecs % 100,
|
|
todo - wq_busy, wq_busy);
|
|
|
|
if (!wakeup) {
|
|
read_lock(&tasklist_lock);
|
|
do_each_thread(g, p) {
|
|
if (p != current && !freezer_should_skip(p)
|
|
&& freezing(p) && !frozen(p))
|
|
sched_show_task(p);
|
|
} while_each_thread(g, p);
|
|
read_unlock(&tasklist_lock);
|
|
}
|
|
} else {
|
|
printk("(elapsed %d.%02d seconds) ", elapsed_csecs / 100,
|
|
elapsed_csecs % 100);
|
|
}
|
|
|
|
return todo ? -EBUSY : 0;
|
|
}
|
|
|
|
/**
|
|
* freeze_processes - Signal user space processes to enter the refrigerator.
|
|
*
|
|
* On success, returns 0. On failure, -errno and system is fully thawed.
|
|
*/
|
|
int freeze_processes(void)
|
|
{
|
|
int error;
|
|
|
|
error = __usermodehelper_disable(UMH_FREEZING);
|
|
if (error)
|
|
return error;
|
|
|
|
if (!pm_freezing)
|
|
atomic_inc(&system_freezing_cnt);
|
|
|
|
printk("Freezing user space processes ... ");
|
|
pm_freezing = true;
|
|
error = try_to_freeze_tasks(true);
|
|
if (!error) {
|
|
printk("done.");
|
|
__usermodehelper_set_disable_depth(UMH_DISABLED);
|
|
oom_killer_disable();
|
|
}
|
|
printk("\n");
|
|
BUG_ON(in_atomic());
|
|
|
|
if (error)
|
|
thaw_processes();
|
|
return error;
|
|
}
|
|
|
|
/**
|
|
* freeze_kernel_threads - Make freezable kernel threads go to the refrigerator.
|
|
*
|
|
* On success, returns 0. On failure, -errno and only the kernel threads are
|
|
* thawed, so as to give a chance to the caller to do additional cleanups
|
|
* (if any) before thawing the userspace tasks. So, it is the responsibility
|
|
* of the caller to thaw the userspace tasks, when the time is right.
|
|
*/
|
|
int freeze_kernel_threads(void)
|
|
{
|
|
int error;
|
|
|
|
printk("Freezing remaining freezable tasks ... ");
|
|
pm_nosig_freezing = true;
|
|
error = try_to_freeze_tasks(false);
|
|
if (!error)
|
|
printk("done.");
|
|
|
|
printk("\n");
|
|
BUG_ON(in_atomic());
|
|
|
|
if (error)
|
|
thaw_kernel_threads();
|
|
return error;
|
|
}
|
|
|
|
void thaw_processes(void)
|
|
{
|
|
struct task_struct *g, *p;
|
|
|
|
if (pm_freezing)
|
|
atomic_dec(&system_freezing_cnt);
|
|
pm_freezing = false;
|
|
pm_nosig_freezing = false;
|
|
|
|
oom_killer_enable();
|
|
|
|
printk("Restarting tasks ... ");
|
|
|
|
thaw_workqueues();
|
|
|
|
read_lock(&tasklist_lock);
|
|
do_each_thread(g, p) {
|
|
__thaw_task(p);
|
|
} while_each_thread(g, p);
|
|
read_unlock(&tasklist_lock);
|
|
|
|
usermodehelper_enable();
|
|
|
|
schedule();
|
|
printk("done.\n");
|
|
}
|
|
|
|
void thaw_kernel_threads(void)
|
|
{
|
|
struct task_struct *g, *p;
|
|
|
|
pm_nosig_freezing = false;
|
|
printk("Restarting kernel threads ... ");
|
|
|
|
thaw_workqueues();
|
|
|
|
read_lock(&tasklist_lock);
|
|
do_each_thread(g, p) {
|
|
if (p->flags & (PF_KTHREAD | PF_WQ_WORKER))
|
|
__thaw_task(p);
|
|
} while_each_thread(g, p);
|
|
read_unlock(&tasklist_lock);
|
|
|
|
schedule();
|
|
printk("done.\n");
|
|
}
|