From b81898e3d2133715e4475d25757595a3e18502ed Mon Sep 17 00:00:00 2001 From: "Paul E. McKenney" Date: Thu, 30 Apr 2020 12:23:11 -0700 Subject: [PATCH] doc: Timer problems can cause RCU CPU stall warnings Over the past few years, there have been several cases where timekeeping bugs have caused RCU CPU stall warnings, particularly during hardware bringup. This commit therefore adds such bugs to the list of things that can result in RCU CPU stall warnings. Signed-off-by: Paul E. McKenney --- Documentation/RCU/stallwarn.rst | 7 +++++++ 1 file changed, 7 insertions(+) diff --git a/Documentation/RCU/stallwarn.rst b/Documentation/RCU/stallwarn.rst index 08bc9aec4606..c9ab6af4d3be 100644 --- a/Documentation/RCU/stallwarn.rst +++ b/Documentation/RCU/stallwarn.rst @@ -87,6 +87,13 @@ warnings: problem really has happened, and seems to be most likely to result in RCU CPU stall warnings for CONFIG_NO_HZ_COMMON=n kernels. +- A hardware or software issue that prevents time-based wakeups + from occurring. These issues can range from misconfigured or + buggy timer hardware through bugs in the interrupt or exception + path (whether hardware, firmware, or software) through bugs + in Linux's timer subsystem through bugs in the scheduler, and, + yes, even including bugs in RCU itself. + - A bug in the RCU implementation. - A hardware failure. This is quite unlikely, but has occurred