The commit is pushed to "branch-rh7-3.10.0-327.36.1.vz7.20.x-ovz" and will
appear at https://src.openvz.org/scm/ovz/vzkernel.git
after rh7-3.10.0-327.36.1.vz7.20.14
------>
commit dc05ea50227f6674afe5c0becfeeb0c4cbd2ada1
Author: John Stultz <[email protected]>
Date: Fri Dec 9 17:50:26 2016 +0400
ms/timekeeping: Copy the shadow-timekeeper over the real timekeeper last
timekeeping: Copy the shadow-timekeeper over the real timekeeper last
The fix in d151832650ed9 (time: Move clock_was_set_seq update
before updating shadow-timekeeper) was unfortunately incomplete.
The main gist of that change was to do the shadow-copy update
last, so that any state changes were properly duplicated, and
we wouldn't accidentally have stale data in the shadow.
Unfortunately in the main update_wall_time() logic, we update
use the shadow-timekeeper to calculate the next update values,
then while holding the lock, copy the shadow-timekeeper over,
then call timekeeping_update() to do some additional
bookkeeping, (skipping the shadow mirror). The bug with this is
the additional bookkeeping isn't all read-only, and some
changes timkeeper state. Thus we might then overwrite this state
change on the next update.
To avoid this problem, do the timekeeping_update() on the
shadow-timekeeper prior to copying the full state over to
the real-timekeeper.
This avoids problems with both the clock_was_set_seq and
next_leap_ktime being overwritten and possibly the
fast-timekeepers as well.
Many thanks to Prarit for his rigorous testing, which discovered
this problem, along with Prarit and Daniel's work validating this
fix.
Reported-by: Prarit Bhargava <[email protected]>
Tested-by: Prarit Bhargava <[email protected]>
Tested-by: Daniel Bristot de Oliveira <[email protected]>
Signed-off-by: John Stultz <[email protected]>
Cc: Richard Cochran <[email protected]>
Cc: Jan Kara <[email protected]>
Cc: Jiri Bohac <[email protected]>
Cc: Ingo Molnar <[email protected]>
Link:
http://lkml.kernel.org/r/[email protected]
Signed-off-by: Thomas Gleixner <[email protected]>
ms commit 906c55579a6360dd9ef5a3101bb2e3ae396dfb97
Bugzilla: http://bugzilla.redhat.com/1344747
Taken from RHEL7.2 3.10.0-327.41.4.el7 kernel.
Conflicts: minor diff conflict due to drift between upstream and RHEL7.
---
kernel/time/timekeeping.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c
index c7aa9b5..1197b73 100644
--- a/kernel/time/timekeeping.c
+++ b/kernel/time/timekeeping.c
@@ -1446,8 +1446,9 @@ void update_wall_time(void)
* memcpy under the timekeeper_seq against one before we start
* updating.
*/
+ timekeeping_update(tk, clock_set);
memcpy(real_tk, tk, sizeof(*tk));
- timekeeping_update(real_tk, clock_set);
+ /* The memcpy must come last. Do not put anything here! */
write_seqcount_end(&timekeeper_seq);
out:
raw_spin_unlock_irqrestore(&timekeeper_lock, flags);
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