Lines Matching refs:CPU
1 Using RCU's CPU Stall Detector
3 This document first discusses what sorts of issues RCU's CPU stall
9 What Causes RCU CPU Stall Warnings?
11 So your kernel printed an RCU CPU stall warning. The next question is
12 "What caused it?" The following problems can result in RCU CPU stall
15 o A CPU looping in an RCU read-side critical section.
17 o A CPU looping with interrupts disabled.
19 o A CPU looping with preemption disabled.
21 o A CPU looping with bottom halves disabled.
23 o For !CONFIG_PREEMPT kernels, a CPU looping anywhere in the kernel
32 RCU CPU stall warning messages. Especially if you have added
42 o A CPU-bound real-time task in a CONFIG_PREEMPT kernel, which might
45 that low-priority task is not permitted to run on any other CPU,
51 o A CPU-bound real-time task in a CONFIG_PREEMPT_RT kernel that
72 RCU CPU stall warnings.
75 timeout down to just barely avoid RCU CPU stall warnings, and then
81 interrupt on a CPU that is not in dyntick-idle mode. This
83 result in RCU CPU stall warnings for CONFIG_NO_HZ_COMMON=n kernels.
88 at least once in real life. A CPU failed in a running system,
90 This resulted in a series of RCU CPU stall warnings, eventually
91 leading the realization that the CPU had failed.
93 The RCU, RCU-sched, and RCU-tasks implementations have CPU stall warning.
94 Note that SRCU does -not- have CPU stall warnings. Please note that
95 RCU only detects CPU stalls when there is a grace period in progress.
96 No grace period, no CPU stall warnings.
111 Fine-Tuning the RCU CPU Stall Detector
114 CPU stall detector, which detects conditions that unduly delay RCU grace
115 periods. This module parameter enables CPU stall detection by default,
124 issues an RCU CPU stall warning. This time period is normally
144 giving an RCU CPU stall warning message. (This is a cpp
149 The CPU stall detector tries to make the offending CPU print its
151 However, if the offending CPU does not detect its own stall in
153 some other CPU will complain. This delay is normally set to
170 Interpreting RCU's CPU Stall-Detector "Splats"
172 For non-RCU-tasks flavors of RCU, when a CPU detects that it is stalling,
180 This message indicates that CPU 32 detected that CPUs 2 and 16 were both
182 will normally be followed by stack dumps for each CPU. Please note that
188 CPU 2's "(3 GPs behind)" indicates that this CPU has not interacted with
189 the RCU core for the past three grace periods. In contrast, CPU 16's "(0
190 ticks this GP)" indicates that this CPU has not taken any scheduling-clock
195 dynticks counter, which will have an even-numbered value if the CPU
202 handlers that the stalled CPU has executed. The number before the "/"
203 is the number that had executed since boot at the time that this CPU
206 example, if the CPU might have been in dyntick-idle mode for an extended
210 handlers are no longer able to execute on this CPU. This can happen if
211 the stalled CPU is spinning with interrupts are disabled, or, in -rt
216 CPU since the last time that this CPU noted the beginning of a grace
219 The "detected by" line indicates which CPU detected the stall (in this
220 case, CPU 32), how many jiffies have elapsed since the start of the grace
226 for each CPU:
231 jiffies counter when this CPU last invoked rcu_try_advance_all_cbs()
273 Starving the grace-period kthreads of CPU time can of course result
274 in RCU CPU stall warnings even when all CPUs and tasks have passed
280 kthread last ran on CPU 5.
299 This indicates that CPU 7 has failed to respond to a reschedule IPI.
300 The three periods (".") following the CPU number indicate that the CPU
302 that the CPU was online at the beginning of the expedited grace period
304 the CPU has been online at least once since boot (otherwise, the third