doc: Update stallwarn.rst
This commit updates stallwarn.rst to reflect RCU additions and changes over the past few years. Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
This commit is contained in:
parent
647dd4cd7c
commit
3abf176d64
|
@ -25,10 +25,10 @@ warnings:
|
|||
|
||||
- A CPU looping with bottom halves disabled.
|
||||
|
||||
- For !CONFIG_PREEMPTION kernels, a CPU looping anywhere in the kernel
|
||||
without invoking schedule(). If the looping in the kernel is
|
||||
really expected and desirable behavior, you might need to add
|
||||
some calls to cond_resched().
|
||||
- For !CONFIG_PREEMPTION kernels, a CPU looping anywhere in the
|
||||
kernel without potentially invoking schedule(). If the looping
|
||||
in the kernel is really expected and desirable behavior, you
|
||||
might need to add some calls to cond_resched().
|
||||
|
||||
- Booting Linux using a console connection that is too slow to
|
||||
keep up with the boot-time console-message rate. For example,
|
||||
|
@ -108,16 +108,17 @@ warnings:
|
|||
|
||||
- A bug in the RCU implementation.
|
||||
|
||||
- A hardware failure. This is quite unlikely, but has occurred
|
||||
at least once in real life. A CPU failed in a running system,
|
||||
becoming unresponsive, but not causing an immediate crash.
|
||||
This resulted in a series of RCU CPU stall warnings, eventually
|
||||
leading the realization that the CPU had failed.
|
||||
- A hardware failure. This is quite unlikely, but is not at all
|
||||
uncommon in large datacenter. In one memorable case some decades
|
||||
back, a CPU failed in a running system, becoming unresponsive,
|
||||
but not causing an immediate crash. This resulted in a series
|
||||
of RCU CPU stall warnings, eventually leading the realization
|
||||
that the CPU had failed.
|
||||
|
||||
The RCU, RCU-sched, and RCU-tasks implementations have CPU stall warning.
|
||||
Note that SRCU does *not* have CPU stall warnings. Please note that
|
||||
RCU only detects CPU stalls when there is a grace period in progress.
|
||||
No grace period, no CPU stall warnings.
|
||||
The RCU, RCU-sched, RCU-tasks, and RCU-tasks-trace implementations have
|
||||
CPU stall warning. Note that SRCU does *not* have CPU stall warnings.
|
||||
Please note that RCU only detects CPU stalls when there is a grace period
|
||||
in progress. No grace period, no CPU stall warnings.
|
||||
|
||||
To diagnose the cause of the stall, inspect the stack traces.
|
||||
The offending function will usually be near the top of the stack.
|
||||
|
@ -205,16 +206,21 @@ RCU_STALL_RAT_DELAY
|
|||
rcupdate.rcu_task_stall_timeout
|
||||
-------------------------------
|
||||
|
||||
This boot/sysfs parameter controls the RCU-tasks stall warning
|
||||
interval. A value of zero or less suppresses RCU-tasks stall
|
||||
warnings. A positive value sets the stall-warning interval
|
||||
in seconds. An RCU-tasks stall warning starts with the line:
|
||||
This boot/sysfs parameter controls the RCU-tasks and
|
||||
RCU-tasks-trace stall warning intervals. A value of zero or less
|
||||
suppresses RCU-tasks stall warnings. A positive value sets the
|
||||
stall-warning interval in seconds. An RCU-tasks stall warning
|
||||
starts with the line:
|
||||
|
||||
INFO: rcu_tasks detected stalls on tasks:
|
||||
|
||||
And continues with the output of sched_show_task() for each
|
||||
task stalling the current RCU-tasks grace period.
|
||||
|
||||
An RCU-tasks-trace stall warning starts (and continues) similarly:
|
||||
|
||||
INFO: rcu_tasks_trace detected stalls on tasks
|
||||
|
||||
|
||||
Interpreting RCU's CPU Stall-Detector "Splats"
|
||||
==============================================
|
||||
|
@ -248,7 +254,8 @@ dynticks counter, which will have an even-numbered value if the CPU
|
|||
is in dyntick-idle mode and an odd-numbered value otherwise. The hex
|
||||
number between the two "/"s is the value of the nesting, which will be
|
||||
a small non-negative number if in the idle loop (as shown above) and a
|
||||
very large positive number otherwise.
|
||||
very large positive number otherwise. The number following the final
|
||||
"/" is the NMI nesting, which will be a small non-negative number.
|
||||
|
||||
The "softirq=" portion of the message tracks the number of RCU softirq
|
||||
handlers that the stalled CPU has executed. The number before the "/"
|
||||
|
|
Loading…
Reference in New Issue