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-rw-r--r--include/linux/freezer.h10
-rw-r--r--include/linux/sched.h1
-rw-r--r--kernel/kthread.c2
-rw-r--r--kernel/power/process.c97
4 files changed, 54 insertions, 56 deletions
diff --git a/include/linux/freezer.h b/include/linux/freezer.h
index 0893499..deddeed 100644
--- a/include/linux/freezer.h
+++ b/include/linux/freezer.h
@@ -128,6 +128,15 @@ static inline void set_freezable(void)
}
/*
+ * Tell the freezer that the current task should be frozen by it and that it
+ * should send a fake signal to the task to freeze it.
+ */
+static inline void set_freezable_with_signal(void)
+{
+ current->flags &= ~(PF_NOFREEZE | PF_FREEZER_NOSIG);
+}
+
+/*
* Freezer-friendly wrappers around wait_event_interruptible() and
* wait_event_interruptible_timeout(), originally defined in <linux/wait.h>
*/
@@ -174,6 +183,7 @@ static inline void freezer_do_not_count(void) {}
static inline void freezer_count(void) {}
static inline int freezer_should_skip(struct task_struct *p) { return 0; }
static inline void set_freezable(void) {}
+static inline void set_freezable_with_signal(void) {}
#define wait_event_freezable(wq, condition) \
wait_event_interruptible(wq, condition)
diff --git a/include/linux/sched.h b/include/linux/sched.h
index 2134917..ba2f859 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1494,6 +1494,7 @@ static inline void put_task_struct(struct task_struct *t)
#define PF_MEMPOLICY 0x10000000 /* Non-default NUMA mempolicy */
#define PF_MUTEX_TESTER 0x20000000 /* Thread belongs to the rt mutex tester */
#define PF_FREEZER_SKIP 0x40000000 /* Freezer should not count it as freezeable */
+#define PF_FREEZER_NOSIG 0x80000000 /* Freezer won't send signals to it */
/*
* Only the _current_ task can read/write to tsk->flags, but other
diff --git a/kernel/kthread.c b/kernel/kthread.c
index 97747cd..ac3fb73 100644
--- a/kernel/kthread.c
+++ b/kernel/kthread.c
@@ -235,7 +235,7 @@ int kthreadd(void *unused)
set_user_nice(tsk, KTHREAD_NICE_LEVEL);
set_cpus_allowed(tsk, CPU_MASK_ALL);
- current->flags |= PF_NOFREEZE;
+ current->flags |= PF_NOFREEZE | PF_FREEZER_NOSIG;
for (;;) {
set_current_state(TASK_INTERRUPTIBLE);
diff --git a/kernel/power/process.c b/kernel/power/process.c
index f1d0b34..5fb8765 100644
--- a/kernel/power/process.c
+++ b/kernel/power/process.c
@@ -19,9 +19,6 @@
*/
#define TIMEOUT (20 * HZ)
-#define FREEZER_KERNEL_THREADS 0
-#define FREEZER_USER_SPACE 1
-
static inline int freezeable(struct task_struct * p)
{
if ((p == current) ||
@@ -84,63 +81,53 @@ static void fake_signal_wake_up(struct task_struct *p)
spin_unlock_irqrestore(&p->sighand->siglock, flags);
}
-static int has_mm(struct task_struct *p)
+static inline bool should_send_signal(struct task_struct *p)
{
- return (p->mm && !(p->flags & PF_BORROWED_MM));
+ return !(p->flags & PF_FREEZER_NOSIG);
}
/**
* freeze_task - send a freeze request to given task
* @p: task to send the request to
- * @with_mm_only: if set, the request will only be sent if the task has its
- * own mm
- * Return value: 0, if @with_mm_only is set and the task has no mm of its
- * own or the task is frozen, 1, otherwise
+ * @sig_only: if set, the request will only be sent if the task has the
+ * PF_FREEZER_NOSIG flag unset
+ * Return value: 'false', if @sig_only is set and the task has
+ * PF_FREEZER_NOSIG set or the task is frozen, 'true', otherwise
*
- * The freeze request is sent by seting the tasks's TIF_FREEZE flag and
+ * The freeze request is sent by setting the tasks's TIF_FREEZE flag and
* either sending a fake signal to it or waking it up, depending on whether
- * or not it has its own mm (ie. it is a user land task). If @with_mm_only
- * is set and the task has no mm of its own (ie. it is a kernel thread),
- * its TIF_FREEZE flag should not be set.
- *
- * The task_lock() is necessary to prevent races with exit_mm() or
- * use_mm()/unuse_mm() from occuring.
+ * or not it has PF_FREEZER_NOSIG set. If @sig_only is set and the task
+ * has PF_FREEZER_NOSIG set (ie. it is a typical kernel thread), its
+ * TIF_FREEZE flag will not be set.
*/
-static int freeze_task(struct task_struct *p, int with_mm_only)
+static bool freeze_task(struct task_struct *p, bool sig_only)
{
- int ret = 1;
+ /*
+ * We first check if the task is freezing and next if it has already
+ * been frozen to avoid the race with frozen_process() which first marks
+ * the task as frozen and next clears its TIF_FREEZE.
+ */
+ if (!freezing(p)) {
+ rmb();
+ if (frozen(p))
+ return false;
- task_lock(p);
- if (freezing(p)) {
- if (has_mm(p)) {
- if (!signal_pending(p))
- fake_signal_wake_up(p);
- } else {
- if (with_mm_only)
- ret = 0;
- else
- wake_up_state(p, TASK_INTERRUPTIBLE);
- }
+ if (!sig_only || should_send_signal(p))
+ set_freeze_flag(p);
+ else
+ return false;
+ }
+
+ if (should_send_signal(p)) {
+ if (!signal_pending(p))
+ fake_signal_wake_up(p);
+ } else if (sig_only) {
+ return false;
} else {
- rmb();
- if (frozen(p)) {
- ret = 0;
- } else {
- if (has_mm(p)) {
- set_freeze_flag(p);
- fake_signal_wake_up(p);
- } else {
- if (with_mm_only) {
- ret = 0;
- } else {
- set_freeze_flag(p);
- wake_up_state(p, TASK_INTERRUPTIBLE);
- }
- }
- }
+ wake_up_state(p, TASK_INTERRUPTIBLE);
}
- task_unlock(p);
- return ret;
+
+ return true;
}
static void cancel_freezing(struct task_struct *p)
@@ -156,7 +143,7 @@ static void cancel_freezing(struct task_struct *p)
}
}
-static int try_to_freeze_tasks(int freeze_user_space)
+static int try_to_freeze_tasks(bool sig_only)
{
struct task_struct *g, *p;
unsigned long end_time;
@@ -175,7 +162,7 @@ static int try_to_freeze_tasks(int freeze_user_space)
if (frozen(p) || !freezeable(p))
continue;
- if (!freeze_task(p, freeze_user_space))
+ if (!freeze_task(p, sig_only))
continue;
/*
@@ -235,13 +222,13 @@ int freeze_processes(void)
int error;
printk("Freezing user space processes ... ");
- error = try_to_freeze_tasks(FREEZER_USER_SPACE);
+ error = try_to_freeze_tasks(true);
if (error)
goto Exit;
printk("done.\n");
printk("Freezing remaining freezable tasks ... ");
- error = try_to_freeze_tasks(FREEZER_KERNEL_THREADS);
+ error = try_to_freeze_tasks(false);
if (error)
goto Exit;
printk("done.");
@@ -251,7 +238,7 @@ int freeze_processes(void)
return error;
}
-static void thaw_tasks(int thaw_user_space)
+static void thaw_tasks(bool nosig_only)
{
struct task_struct *g, *p;
@@ -260,7 +247,7 @@ static void thaw_tasks(int thaw_user_space)
if (!freezeable(p))
continue;
- if (!p->mm == thaw_user_space)
+ if (nosig_only && should_send_signal(p))
continue;
thaw_process(p);
@@ -271,8 +258,8 @@ static void thaw_tasks(int thaw_user_space)
void thaw_processes(void)
{
printk("Restarting tasks ... ");
- thaw_tasks(FREEZER_KERNEL_THREADS);
- thaw_tasks(FREEZER_USER_SPACE);
+ thaw_tasks(true);
+ thaw_tasks(false);
schedule();
printk("done.\n");
}
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