kernel-ark/kernel/power/process.c
Rafael J. Wysocki 181e9bdef3 PM / Hibernate: Fix s2disk regression related to freezing workqueues
Commit 2aede851dd

  PM / Hibernate: Freeze kernel threads after preallocating memory

introduced a mechanism by which kernel threads were frozen after
the preallocation of hibernate image memory to avoid problems with
frozen kernel threads not responding to memory freeing requests.
However, it overlooked the s2disk code path in which the
SNAPSHOT_CREATE_IMAGE ioctl was run directly after SNAPSHOT_FREE,
which caused freeze_workqueues_begin() to BUG(), because it saw
that worqueues had been already frozen.

Although in principle this issue might be addressed by removing
the relevant BUG_ON() from freeze_workqueues_begin(), that would
reintroduce the very problem that commit 2aede851dd
attempted to avoid into that particular code path.  For this reason,
to fix the issue at hand, introduce thaw_kernel_threads() and make
the SNAPSHOT_FREE ioctl execute it.

Special thanks to Srivatsa S. Bhat for detailed analysis of the
problem.

Reported-and-tested-by: Jiri Slaby <jslaby@suse.cz>
Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
Acked-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
Cc: stable@kernel.org
2012-01-29 20:35:52 +01:00

210 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>
/*
* 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;
/*
* Now that we've done set_freeze_flag, don't
* perturb a task in TASK_STOPPED or TASK_TRACED.
* It is "frozen enough". If the task does wake
* up, it will immediately call try_to_freeze.
*
* Because freeze_task() goes through p's
* scheduler lock after setting TIF_FREEZE, it's
* guaranteed that either we see TASK_RUNNING or
* try_to_stop() after schedule() in ptrace/signal
* stop sees TIF_FREEZE.
*/
if (!task_is_stopped_or_traced(p) &&
!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 regrigerator.
*/
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);
read_lock(&tasklist_lock);
do_each_thread(g, p) {
if (!wakeup && !freezer_should_skip(p) &&
p != current && 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;
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.");
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 system is fully thawed.
*/
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_processes();
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);
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");
}