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Subject[PATCH] Timekeeping: Fix dead lock in update_wall_time by correct shift convertion.
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update_wall_time() runs into dead lock after kernel traps into kgdb and exits
per user's request some seconds layer. This is root caused to be wrong
calculation of maxshift in update_wall_time().

The shift in update_wall_time() and logarithmic_accumulation() is
clock shift. In order to generate ntp_error and maxshift correctly,
shift convertion between clock and ntp should be done properly.


Signed-off-by: Sonic Zhang <sonic.zhang@analog.com>
---
kernel/time/timekeeping.c | 20 ++++++++++++++------
1 files changed, 14 insertions(+), 6 deletions(-)

diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c
index 1673637..5b47c9e 100644
--- a/kernel/time/timekeeping.c
+++ b/kernel/time/timekeeping.c
@@ -770,10 +770,14 @@ static cycle_t logarithmic_accumulation(cycle_t
offset, int shift)
raw_time.tv_sec++;
}

- /* Accumulate error between NTP and clock interval */
- timekeeper.ntp_error += tick_length << shift;
- timekeeper.ntp_error -= timekeeper.xtime_interval <<
- (timekeeper.ntp_error_shift + shift);
+ /*
+ * Accumulate error between NTP and clock interval.
+ * Paramter shift is clock shift. It should minus shift
+ * conversion between clock and ntp to generate ntp shift.
+ */
+ timekeeper.ntp_error += tick_length <<
+ (shift - timekeeper.ntp_error_shift);
+ timekeeper.ntp_error -= timekeeper.xtime_interval << shift;

return offset;
}
@@ -813,8 +817,12 @@ void update_wall_time(void)
*/
shift = ilog2(offset) - ilog2(timekeeper.cycle_interval);
shift = max(0, shift);
- /* Bound shift to one less then what overflows tick_length */
- maxshift = (8*sizeof(tick_length) - (ilog2(tick_length)+1)) - 1;
+ /*
+ * Bound shift to one less then what overflows tick_length.
+ * Should plus shift conversion between clock and ntp.
+ */
+ maxshift = (8*sizeof(tick_length) - (ilog2(tick_length)+1)) - 1
+ + timekeeper.ntp_error_shift;
shift = min(shift, maxshift);
while (offset >= timekeeper.cycle_interval) {
offset = logarithmic_accumulation(offset, shift);
--
1.6.0





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