Commit-ID: e1333462e3cf933ab860c693ef1ff50775c7ea7f Gitweb: https://git.kernel.org/tip/e1333462e3cf933ab860c693ef1ff50775c7ea7f Author: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx> AuthorDate: Wed, 2 May 2018 12:39:42 -0700 Committer: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx> CommitDate: Thu, 12 Jul 2018 15:38:51 -0700 doc: Update RCU CPU stall-warning documentation Signed-off-by: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx> --- Documentation/RCU/stallwarn.txt | 24 ++++++++++++------------ 1 file changed, 12 insertions(+), 12 deletions(-) diff --git a/Documentation/RCU/stallwarn.txt b/Documentation/RCU/stallwarn.txt index 4259f95c3261..f99cf11b314b 100644 --- a/Documentation/RCU/stallwarn.txt +++ b/Documentation/RCU/stallwarn.txt @@ -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 -- To unsubscribe from this list: send the line "unsubscribe linux-tip-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
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