Add documentation of CONFIG_RCU_CPU_STALL_VERBOSE, CONFIG_RCU_CPU_STALL_INFO,
and RCU_STALL_DELAY_DELTA. Describe multiple stall-warning messages from
a single stall, and the timing of the subsequent messages. Add headings.
Remove RCU_SECONDS_TILL_STALL_RECHECK because this value is now computed
at runtime from RCU_CPU_STALL_TIMEOUT, so that sysfs changes to the timeout
value now directly affect the RCU_SECONDS_TILL_STALL_RECHECK value.
Signed-off-by: Paul E. McKenney <paul.mckenney@linaro.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Update various files in Documentation/RCU to reflect srcu_read_lock_raw()
and srcu_read_unlock_raw(). Credit to Peter Zijlstra for suggesting
use of the existing _raw suffix instead of the earlier bulkref names.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
One of lclaudio's systems was seeing RCU CPU stall warnings from idle.
These turned out to be caused by a bug that stopped scheduling-clock
tick interrupts from being sent to a given CPU for several hundred seconds.
This commit therefore updates the documentation to call this out as a
possible cause for RCU CPU stall warnings.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>
The RCU CPU stall warnings can now be controlled using the
rcu_cpu_stall_suppress boot-time parameter or via the same parameter
from sysfs. There is therefore no longer any reason to have
kernel config parameters for this feature. This commit therefore
removes the RCU_CPU_STALL_DETECTOR and RCU_CPU_STALL_DETECTOR_RUNNABLE
kernel config parameters. The RCU_CPU_STALL_TIMEOUT parameter remains
to allow the timeout to be tuned and the RCU_CPU_STALL_VERBOSE parameter
remains to allow task-stall information to be suppressed if desired.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>
CPU-bound real-time processes can cause RCU CPU stall warnings, and
much other trouble as well. Document the fact that they can cause
RCU CPU stall warnings.
Suggested-by: Darren Hart <dvhltc@us.ibm.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
The existing Documentation/RCU/stallwarn.txt has proven unhelpful, so
rework it a bit. In particular, show how to interpret the stall-warning
messages.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Paul E. McKenney