freezer: shorten freezer sleep time using exponential backoff

All tasks can easily be frozen in under 10 ms, switch to using
an initial 1 ms sleep followed by exponential backoff until
8 ms.  Also convert the printed time to ms instead of centiseconds.

Acked-by: Pavel Machek <pavel@ucw.cz>
Acked-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Colin Cross <ccross@android.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

diff --git a/kernel/power/process.c b/kernel/power/process.c
index 98088e0e71e83a3b9cd157c5415f9e79083592c0..fc0df84864495f8c44261961cb6909e66d24a21e 100644 (file)
--- a/kernel/power/process.c
+++ b/kernel/power/process.c
@@ -30,9 +30,10 @@ static int try_to_freeze_tasks(bool user_only)
        unsigned int todo;
        bool wq_busy = false;
        struct timeval start, end;
-       u64 elapsed_csecs64;
-       unsigned int elapsed_csecs;
+       u64 elapsed_msecs64;
+       unsigned int elapsed_msecs;
        bool wakeup = false;
+       int sleep_usecs = USEC_PER_MSEC;
 
        do_gettimeofday(&start);
 
@@ -68,22 +69,25 @@ static int try_to_freeze_tasks(bool user_only)
 
                /*
                 * We need to retry, but first give the freezing tasks some
-                * time to enter the refrigerator.
+                * time to enter the refrigerator.  Start with an initial
+                * 1 ms sleep followed by exponential backoff until 8 ms.
                 */
-               msleep(10);
+               usleep_range(sleep_usecs / 2, sleep_usecs);
+               if (sleep_usecs < 8 * USEC_PER_MSEC)
+                       sleep_usecs *= 2;
        }
 
        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;
+       elapsed_msecs64 = timeval_to_ns(&end) - timeval_to_ns(&start);
+       do_div(elapsed_msecs64, NSEC_PER_MSEC);
+       elapsed_msecs = elapsed_msecs64;
 
        if (todo) {
                printk("\n");
-               printk(KERN_ERR "Freezing of tasks %s after %d.%02d seconds "
+               printk(KERN_ERR "Freezing of tasks %s after %d.%03d seconds "
                       "(%d tasks refusing to freeze, wq_busy=%d):\n",
                       wakeup ? "aborted" : "failed",
-                      elapsed_csecs / 100, elapsed_csecs % 100,
+                      elapsed_msecs / 1000, elapsed_msecs % 1000,
                       todo - wq_busy, wq_busy);
 
                if (!wakeup) {
@@ -96,8 +100,8 @@ static int try_to_freeze_tasks(bool user_only)
                        read_unlock(&tasklist_lock);
                }
        } else {
-               printk("(elapsed %d.%02d seconds) ", elapsed_csecs / 100,
-                       elapsed_csecs % 100);
+               printk("(elapsed %d.%03d seconds) ", elapsed_msecs / 1000,
+                       elapsed_msecs % 1000);
        }
 
        return todo ? -EBUSY : 0;