diff options
| author | Thomas Gleixner <tglx@linutronix.de> | 2016-10-22 11:07:37 +0000 |
|---|---|---|
| committer | Thomas Gleixner <tglx@linutronix.de> | 2016-10-25 16:32:50 +0200 |
| commit | 6bad6bccf2d717f652d37e63cf261eaa23466009 (patch) | |
| tree | 9a22c3c4a778297bf544a0cc89da0c76c8784d6b | |
| parent | 041ad7bc758db259bb960ef795197dd14aab19a6 (diff) | |
timers: Prevent base clock corruption when forwarding
When a timer is enqueued we try to forward the timer base clock. This
mechanism has two issues:
1) Forwarding a remote base unlocked
The forwarding function is called from get_target_base() with the current
timer base lock held. But if the new target base is a different base than
the current base (can happen with NOHZ, sigh!) then the forwarding is done
on an unlocked base. This can lead to corruption of base->clk.
Solution is simple: Invoke the forwarding after the target base is locked.
2) Possible corruption due to jiffies advancing
This is similar to the issue in get_net_timer_interrupt() which was fixed
in the previous patch. jiffies can advance between check and assignement
and therefore advancing base->clk beyond the next expiry value.
So we need to read jiffies into a local variable once and do the checks and
assignment with the local copy.
Fixes: a683f390b93f("timers: Forward the wheel clock whenever possible")
Reported-by: Ashton Holmes <scoopta@gmail.com>
Reported-by: Michael Thayer <michael.thayer@oracle.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Michal Necasek <michal.necasek@oracle.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: knut.osmundsen@oracle.com
Cc: stable@vger.kernel.org
Cc: stern@rowland.harvard.edu
Cc: rt@linutronix.de
Link: http://lkml.kernel.org/r/20161022110552.253640125@linutronix.de
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>