From: Paul E. McKenney Date: Tue, 31 Dec 2024 16:47:43 +0000 (-0800) Subject: doc: Add broken-timing possibility to stallwarn.rst X-Git-Tag: v6.15-rc1~221^2~7 X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=bea1d19f03644b0eb7ac0b7d96f79a3af13f196b;p=thirdparty%2Flinux.git doc: Add broken-timing possibility to stallwarn.rst 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 Signed-off-by: Boqun Feng --- diff --git a/Documentation/RCU/stallwarn.rst b/Documentation/RCU/stallwarn.rst index 30080ff6f4062..d1ccd6039a8c3 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