Lines Matching refs:CPU
1 Using RCU's CPU Stall Detector
3 The rcu_cpu_stall_suppress module parameter enables RCU's CPU stall
5 This module parameter enables CPU stall detection by default, but
14 issues an RCU CPU stall warning. This time period is normally
34 giving an RCU CPU stall warning message. (This is a cpp
39 The CPU stall detector tries to make the offending CPU print its
41 However, if the offending CPU does not detect its own stall in
43 some other CPU will complain. This delay is normally set to
59 For non-RCU-tasks flavors of RCU, when a CPU detects that it is stalling,
62 INFO: rcu_sched_state detected stall on CPU 5 (t=2500 jiffies)
64 This message indicates that CPU 5 detected that it was causing a stall,
66 followed by a stack dump of the offending CPU. On TREE_RCU kernel builds,
71 On the other hand, if the offending CPU fails to print out a stall-warning
72 message quickly enough, some other CPU will print a message similar to
77 This message indicates that CPU 2 detected that CPUs 3 and 5 were both
79 will normally be followed by stack dumps for each CPU. Please note that
100 INFO: rcu_preempt detected stall on CPU
106 INFO: rcu_preempt detected stall on CPU
110 The "(64628 ticks this GP)" indicates that this CPU has taken more
112 grace period. If the CPU was not yet aware of the current grace
114 indicates how many grace periods behind the CPU is.
118 dynticks counter, which will have an even-numbered value if the CPU is
125 handlers that the stalled CPU has executed. The number before the "/"
126 is the number that had executed since boot at the time that this CPU
129 example, if the CPU might have been in dyntick-idle mode for an extended
133 handlers are no longer able to execute on this CPU. This can happen if
134 the stalled CPU is spinning with interrupts are disabled, or, in -rt
138 low-order 16 bits (in hex) of the jiffies counter when this CPU last
152 Starving the grace-period kthreads of CPU time can of course result in
153 RCU CPU stall warnings even when all CPUs and tasks have passed through
183 What Causes RCU CPU Stall Warnings?
185 So your kernel printed an RCU CPU stall warning. The next question is
186 "What caused it?" The following problems can result in RCU CPU stall
189 o A CPU looping in an RCU read-side critical section.
191 o A CPU looping with interrupts disabled. This condition can
194 o A CPU looping with preemption disabled. This condition can
198 o A CPU looping with bottom halves disabled. This condition can
201 o For !CONFIG_PREEMPT kernels, a CPU looping anywhere in the
203 does not necessarily prevent RCU CPU stall warnings. Therefore,
212 RCU CPU stall warning messages. Especially if you have added
220 o A CPU-bound real-time task in a CONFIG_PREEMPT kernel, which might
223 that low-priority task is not permitted to run on any other CPU,
229 o A CPU-bound real-time task in a CONFIG_PREEMPT_RT kernel that
239 interrupt on a CPU that is not in dyntick-idle mode. This
241 result in RCU CPU stall warnings for CONFIG_NO_HZ_COMMON=n kernels.
246 at least once in real life. A CPU failed in a running system,
248 This resulted in a series of RCU CPU stall warnings, eventually
249 leading the realization that the CPU had failed.
251 The RCU, RCU-sched, RCU-bh, and RCU-tasks implementations have CPU stall
252 warning. Note that SRCU does -not- have CPU stall warnings. Please note
253 that RCU only detects CPU stalls when there is a grace period in progress.
254 No grace period, no CPU stall warnings.