diff options
Diffstat (limited to 'Documentation/RCU/stallwarn.txt')
| -rw-r--r-- | Documentation/RCU/stallwarn.txt | 20 |
1 files changed, 8 insertions, 12 deletions
diff --git a/Documentation/RCU/stallwarn.txt b/Documentation/RCU/stallwarn.txt index f99cf11b314b..073dbc12d1ea 100644 --- a/Documentation/RCU/stallwarn.txt +++ b/Documentation/RCU/stallwarn.txt @@ -16,12 +16,9 @@ o A CPU looping in an RCU read-side critical section. o A CPU looping with interrupts disabled. -o A CPU looping with preemption disabled. This condition can - result in RCU-sched stalls and, if ksoftirqd is in use, RCU-bh - stalls. +o A CPU looping with preemption disabled. -o A CPU looping with bottom halves disabled. This condition can - result in RCU-sched and RCU-bh stalls. +o A CPU looping with bottom halves disabled. o For !CONFIG_PREEMPT kernels, a CPU looping anywhere in the kernel without invoking schedule(). If the looping in the kernel is @@ -87,9 +84,9 @@ o A hardware failure. This is quite unlikely, but has occurred This resulted in a series of RCU CPU stall warnings, eventually leading the realization that the CPU had failed. -The RCU, RCU-sched, RCU-bh, 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. +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. To diagnose the cause of the stall, inspect the stack traces. @@ -179,9 +176,8 @@ causing stalls, and that the stall was affecting RCU-sched. This message will normally be followed by stack dumps for each CPU. Please note that PREEMPT_RCU builds can be stalled by tasks as well as by CPUs, and that the tasks will be indicated by PID, for example, "P3421". It is even -possible for a rcu_preempt_state stall to be caused by both CPUs -and- -tasks, in which case the offending CPUs and tasks will all be called -out in the list. +possible for an rcu_state stall to be caused by both CPUs -and- tasks, +in which case the offending CPUs and tasks will all be called out in the list. CPU 2's "(3 GPs behind)" indicates that this CPU has not interacted with the RCU core for the past three grace periods. In contrast, CPU 16's "(0 @@ -209,7 +205,7 @@ handlers are no longer able to execute on this CPU. This can happen if the stalled CPU is spinning with interrupts are disabled, or, in -rt kernels, if a high-priority process is starving RCU's softirq handler. -The "fps=" shows the number of force-quiescent-state idle/offline +The "fqs=" shows the number of force-quiescent-state idle/offline detection passes that the grace-period kthread has made across this CPU since the last time that this CPU noted the beginning of a grace period. |