Documentation/RCU/stallwarn.rst

9 options that can be used to fine-tune the detector's operation.  Finally,
33 -	Booting Linux using a console connection that is too slow to
40 -	Anything that prevents RCU's grace-period kthreads from running.
50 	that low-priority task is not permitted to run on any other CPU,
56 -	A CPU-bound real-time task in a CONFIG_PREEMPT_RT kernel that
67 	help avoid this problem.  However, please note that doing this
74 	Note that certain high-overhead debugging options, for example
82 	slow system.  Note that thermal throttling and on-demand governors
86 	interrupt on a CPU that is not in dyntick-idle mode.  This
90 -	A hardware or software issue that prevents time-based wakeups
103 	leading the realization that the CPU had failed.
106 Note that SRCU does -not- have CPU stall warnings.  Please note that
115 that portion of the stack which remains the same from trace to trace.
127 CPU stall detector, which detects conditions that unduly delay RCU grace
137 	that RCU will wait from the beginning of a grace period until it
190 For non-RCU-tasks flavors of RCU, when a CPU detects that it is stalling,
198 This message indicates that CPU 32 detected that CPUs 2 and 16 were both
199 causing stalls, and that the stall was affecting RCU-sched.  This message
200 will normally be followed by stack dumps for each CPU.  Please note that
201 PREEMPT_RCU builds can be stalled by tasks as well as by CPUs, and that
206 CPU 2's "(3 GPs behind)" indicates that this CPU has not interacted with
208 ticks this GP)" indicates that this CPU has not taken any scheduling-clock
220 handlers that the stalled CPU has executed.  The number before the "/"
221 is the number that had executed since boot at the time that this CPU
225 time period.  The number after the "/" is the number that have executed
227 across repeated stall-warning messages, it is possible that RCU's softirq
233 detection passes that the grace-period kthread has made across this
234 CPU since the last time that this CPU noted the beginning of a grace
251 rcu_prepare_for_idle(). "dyntick_enabled: 1" indicates that dyntick-idle
263 interact.  Please note that it is not possible to entirely eliminate this
273 The "23807" indicates that it has been more than 23 thousand jiffies
275 indicates how frequently that kthread should run, giving the number
290 to the grace-period kthread, the "RCU_GP_WAIT_FQS" indicates that the
292 task_struct ->state field, and the "cpu" indicates that the grace-period
301 longer intervals, so that the time between (say) the first and second
314 This indicates that CPU 7 has failed to respond to a reschedule IPI.
315 The three periods (".") following the CPU number indicate that the CPU
317 that the CPU was online at the beginning of the expedited grace period
318 (otherwise the second period would have instead been "o"), and that
321 indicates that the expedited grace period has been going on for 21,119
322 jiffies.  The number following the "s:" indicates that the expedited
323 grace-period sequence counter is 73.  The fact that this last value is
324 odd indicates that an expedited grace period is in flight.  The number
325 following "root:" is a bitmask that indicates which children of the root
326 rcu_node structure correspond to CPUs and/or tasks that are blocking the
332 tasks as well as by CPUs, and that the tasks will be indicated by PID,