Commit 13bc8fa8 authored by Paul E. McKenney's avatar Paul E. McKenney
Browse files

doc: Add another stall-warning root cause in stallwarn.rst 



This commit adds a bullet item noting that both deficiencies and surpluses
of calls to rcu_*_enter() and rcu_*_exit() can result in RCU CPU stall
warnings.

Signed-off-by: default avatarPaul E. McKenney <paulmck@kernel.org>
parent 9424b867

Documentation/RCU/stallwarn.rst

+10 −0
Original line number Diff line number Diff line
@@ -96,6 +96,16 @@ warnings: 
	the ``rcu_.*timer wakeup didn't happen for`` console-log message,

	which will include additional debugging information.



-	A low-level kernel issue that either fails to invoke one of the

	variants of rcu_user_enter(), rcu_user_exit(), rcu_idle_enter(),

	rcu_idle_exit(), rcu_irq_enter(), or rcu_irq_exit() on the one

	hand, or that invokes one of them too many times on the other.

	Historically, the most frequent issue has been an omission

	of either irq_enter() or irq_exit(), which in turn invoke

	rcu_irq_enter() or rcu_irq_exit(), respectively.  Building your

	kernel with CONFIG_RCU_EQS_DEBUG=y can help track down these types

	of issues, which sometimes arise in architecture-specific code.



-	A bug in the RCU implementation.



-	A hardware failure.  This is quite unlikely, but has occurred