From: "Paul E. McKenney" <paulmck@xxxxxxxxxx> Currently, stallwarn.rst does not mention the fact that timer bugs can result in false-positive RCU CPU stall warnings. This commit therefore adds this to the list. Signed-off-by: Paul E. McKenney <paulmck@xxxxxxxxxx> Signed-off-by: Boqun Feng <boqun.feng@xxxxxxxxx> --- Documentation/RCU/stallwarn.rst | 7 +++++++ 1 file changed, 7 insertions(+) diff --git a/Documentation/RCU/stallwarn.rst b/Documentation/RCU/stallwarn.rst index 30080ff6f406..d1ccd6039a8c 100644 --- a/Documentation/RCU/stallwarn.rst +++ b/Documentation/RCU/stallwarn.rst @@ -96,6 +96,13 @@ warnings: the ``rcu_.*timer wakeup didn't happen for`` console-log message, which will include additional debugging information. +- A timer issue causes time to appear to jump forward, so that RCU + believes that the RCU CPU stall-warning timeout has been exceeded + when in fact much less time has passed. This could be due to + timer hardware bugs, timer driver bugs, or even corruption of + the "jiffies" global variable. These sorts of timer hardware + and driver bugs are not uncommon when testing new hardware. + - A low-level kernel issue that either fails to invoke one of the variants of rcu_eqs_enter(true), rcu_eqs_exit(true), ct_idle_enter(), ct_idle_exit(), ct_irq_enter(), or ct_irq_exit() on the one -- 2.39.5 (Apple Git-154)
