brain-hackers_pepepper-mirror/linux-brain
1
0
Fork 0
mirror of https://github.com/brain-hackers/linux-brain.git synced 2024-06-09 23:36:23 +09:00
Code Issues Projects Releases Wiki Activity

doc: Update RCU CPU stall-warning documentation

Browse Source 
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
This commit is contained in:
Paul E. McKenney 2018-05-02 12:39:42 -07:00
parent 869cc745bf
commit e1333462e3
1 changed files with 12 additions and 12 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

24
Documentation/RCU/stallwarn.txt
View File

@ -172,7 +172,7 @@ it will print a message similar to the following:
INFO: rcu_sched detected stalls on CPUs/tasks:
2-...: (3 GPs behind) idle=06c/0/0 softirq=1453/1455 fqs=0
16-...: (0 ticks this GP) idle=81c/0/0 softirq=764/764 fqs=0
(detected by 32, t=2603 jiffies, g=7073, c=7072, q=625)
(detected by 32, t=2603 jiffies, g=7075, q=625)
This message indicates that CPU 32 detected that CPUs 2 and 16 were both
causing stalls, and that the stall was affecting RCU-sched. This message
@ -215,11 +215,10 @@ CPU since the last time that this CPU noted the beginning of a grace
period.
The "detected by" line indicates which CPU detected the stall (in this
case, CPU 32), how many jiffies have elapsed since the start of the
grace period (in this case 2603), the number of the last grace period
to start and to complete (7073 and 7072, respectively), and an estimate
of the total number of RCU callbacks queued across all CPUs (625 in
this case).
case, CPU 32), how many jiffies have elapsed since the start of the grace
period (in this case 2603), the grace-period sequence number (7075), and
an estimate of the total number of RCU callbacks queued across all CPUs
(625 in this case).
In kernels with CONFIG_RCU_FAST_NO_HZ, more information is printed
for each CPU:
@ -266,15 +265,16 @@ If the relevant grace-period kthread has been unable to run prior to
the stall warning, as was the case in the "All QSes seen" line above,
the following additional line is printed:
kthread starved for 23807 jiffies! g7073 c7072 f0x0 RCU_GP_WAIT_FQS(3) ->state=0x1
kthread starved for 23807 jiffies! g7075 f0x0 RCU_GP_WAIT_FQS(3) ->state=0x1 ->cpu=5
Starving the grace-period kthreads of CPU time can of course result
in RCU CPU stall warnings even when all CPUs and tasks have passed
through the required quiescent states. The "g" and "c" numbers flag the
number of the last grace period started and completed, respectively,
the "f" precedes the ->gp_flags command to the grace-period kthread,
the "RCU_GP_WAIT_FQS" indicates that the kthread is waiting for a short
timeout, and the "state" precedes value of the task_struct ->state field.
through the required quiescent states. The "g" number shows the current
grace-period sequence number, the "f" precedes the ->gp_flags command
to the grace-period kthread, the "RCU_GP_WAIT_FQS" indicates that the
kthread is waiting for a short timeout, the "state" precedes value of the
task_struct ->state field, and the "cpu" indicates that the grace-period
kthread last ran on CPU 5.
Multiple Warnings From One Stall