time: Fix adjustment cleanup bug in timekeeping_adjust()

Tetsuo Handa reported that sporadically the system clock starts
counting up too quickly which is enough to confuse the hangcheck
timer to print a bogus stall warning.

Commit 2a8c0883 "time: Move xtime_nsec adjustment underflow handling
timekeeping_adjust" overlooked this exit path:

        } else
                return;

which should really be a proper exit sequence, fixing the bug as a
side effect.

Also make the flow more readable by properly balancing curly
braces.

Reported-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> wrote:
Tested-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> wrote:
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Cc: john.stultz@linaro.org
Cc: a.p.zijlstra@chello.nl
Cc: richardcochran@gmail.com
Cc: prarit@redhat.com
Link: http://lkml.kernel.org/r/20120804192114.GA28347@gmail.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>

1 files changed, 17 insertions, 14 deletions

diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c
index 2988bc819187..e16af197a2bc 100644
--- a/kernel/time/timekeeping.c
+++ b/kernel/time/timekeeping.c
@@ -923,20 +923,22 @@ static void timekeeping_adjust(struct timekeeper *tk, s64 offset)
                 if (likely(error <= interval))
                         adj = 1;
                 else
-                        adj = timekeeping_bigadjust(tk, error, &interval,
-                                                        &offset);
-        } else if (error < -interval) {
-                /* See comment above, this is just switched for the negative */
-                error >>= 2;
-                if (likely(error >= -interval)) {
-                        adj = -1;
-                        interval = -interval;
-                        offset = -offset;
-                } else
-                        adj = timekeeping_bigadjust(tk, error, &interval,
-                                                        &offset);
-        } else
-                return;
+                        adj = timekeeping_bigadjust(tk, error, &interval, &offset);
+        } else {
+                if (error < -interval) {
+                        /* See comment above, this is just switched for the negative */
+                        error >>= 2;
+                        if (likely(error >= -interval)) {
+                                adj = -1;
+                                interval = -interval;
+                                offset = -offset;
+                        } else {
+                                adj = timekeeping_bigadjust(tk, error, &interval, &offset);
+                        }
+                } else {
+                        goto out_adjust;
+                }
+        }
 
         if (unlikely(tk->clock->maxadj &&
                 (tk->mult + adj > tk->clock->mult + tk->clock->maxadj))) {
@@ -999,6 +1001,7 @@ static void timekeeping_adjust(struct timekeeper *tk, s64 offset)
         tk->xtime_nsec -= offset;
         tk->ntp_error -= (interval - offset) << tk->ntp_error_shift;
 
+out_adjust:
         /*
          * It may be possible that when we entered this function, xtime_nsec
          * was very small.  Further, if we're slightly speeding the clocksource