container freezer: make refrigerator always available

Now that the TIF_FREEZE flag is available in all architectures, extract
the refrigerator() and freeze_task() from kernel/power/process.c and make
it available to all.

The refrigerator() can now be used in a control group subsystem
implementing a control group freezer.

Signed-off-by: Cedric Le Goater <clg@fr.ibm.com>
Signed-off-by: Matt Helsley <matthltc@us.ibm.com>
Acked-by: Serge E. Hallyn <serue@us.ibm.com>
Tested-by: Matt Helsley <matthltc@us.ibm.com>
Cc: "Rafael J. Wysocki" <rjw@sisk.pl>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 122 insertions, 0 deletions

diff --git a/kernel/freezer.c b/kernel/freezer.c
new file mode 100644
index 000000000000..cb0931f89306
--- /dev/null
+++ b/kernel/freezer.c
@@ -0,0 +1,122 @@
+/*
+ * kernel/freezer.c - Function to freeze a process
+ *
+ * Originally from kernel/power/process.c
+ */
+
+#include <linux/interrupt.h>
+#include <linux/suspend.h>
+#include <linux/module.h>
+#include <linux/syscalls.h>
+#include <linux/freezer.h>
+
+/*
+ * freezing is complete, mark current process as frozen
+ */
+static inline void frozen_process(void)
+{
+        if (!unlikely(current->flags & PF_NOFREEZE)) {
+                current->flags |= PF_FROZEN;
+                wmb();
+        }
+        clear_freeze_flag(current);
+}
+
+/* Refrigerator is place where frozen processes are stored :-). */
+void refrigerator(void)
+{
+        /* Hmm, should we be allowed to suspend when there are realtime
+           processes around? */
+        long save;
+
+        task_lock(current);
+        if (freezing(current)) {
+                frozen_process();
+                task_unlock(current);
+        } else {
+                task_unlock(current);
+                return;
+        }
+        save = current->state;
+        pr_debug("%s entered refrigerator\n", current->comm);
+
+        spin_lock_irq(&current->sighand->siglock);
+        recalc_sigpending(); /* We sent fake signal, clean it up */
+        spin_unlock_irq(&current->sighand->siglock);
+
+        for (;;) {
+                set_current_state(TASK_UNINTERRUPTIBLE);
+                if (!frozen(current))
+                        break;
+                schedule();
+        }
+        pr_debug("%s left refrigerator\n", current->comm);
+        __set_current_state(save);
+}
+EXPORT_SYMBOL(refrigerator);
+
+static void fake_signal_wake_up(struct task_struct *p)
+{
+        unsigned long flags;
+
+        spin_lock_irqsave(&p->sighand->siglock, flags);
+        signal_wake_up(p, 0);
+        spin_unlock_irqrestore(&p->sighand->siglock, flags);
+}
+
+/**
+ *      freeze_task - send a freeze request to given task
+ *      @p: task to send the request to
+ *      @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 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 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.
+ */
+bool freeze_task(struct task_struct *p, bool sig_only)
+{
+        /*
+         * 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;
+
+                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 {
+                wake_up_state(p, TASK_INTERRUPTIBLE);
+        }
+
+        return true;
+}
+
+void cancel_freezing(struct task_struct *p)
+{
+        unsigned long flags;
+
+        if (freezing(p)) {
+                pr_debug("  clean up: %s\n", p->comm);
+                clear_freeze_flag(p);
+                spin_lock_irqsave(&p->sighand->siglock, flags);
+                recalc_sigpending_and_wake(p);
+                spin_unlock_irqrestore(&p->sighand->siglock, flags);
+        }
+}