From 2ccaff10f71307ad4f75ce673b815d3fe6254e3d Mon Sep 17 00:00:00 2001 From: "Paul E. McKenney" Date: Wed, 12 Dec 2018 12:32:06 -0800 Subject: rcu: Add sysrq rcu_node-dump capability Life is hard if RCU manages to get stuck without triggering RCU CPU stall warnings or triggering the rcu_check_gp_start_stall() checks for failing to start a grace period. This commit therefore adds a boot-time-selectable sysrq key (commandeering "y") that allows manually dumping Tree RCU state. The new rcutree.sysrq_rcu kernel boot parameter must be set for this sysrq to be available. Signed-off-by: Paul E. McKenney --- Documentation/admin-guide/kernel-parameters.txt | 5 +++++ 1 file changed, 5 insertions(+) (limited to 'Documentation/admin-guide') diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt index b799bcf67d7b..b0dbb2fa401f 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -3721,6 +3721,11 @@ This wake_up() will be accompanied by a WARN_ONCE() splat and an ftrace_dump(). + rcutree.sysrq_rcu= [KNL] + Commandeer a sysrq key to dump out Tree RCU's + rcu_node tree with an eye towards determining + why a new grace period has not yet started. + rcuperf.gp_async= [KNL] Measure performance of asynchronous grace-period primitives such as call_rcu(). -- cgit v1.2.3 From 1a4762b9272f513aa4c7d8abe7a7529540f95e2d Mon Sep 17 00:00:00 2001 From: "Paul E. McKenney" Date: Tue, 20 Nov 2018 10:22:00 -0800 Subject: doc: Now jiffies_till_sched_qs solicits help from cond_resched() The rcutree.jiffies_till_sched_qs kernel boot parameter used to solicit help only from rcu_note_context_switch(), but now also solicits help from cond_resched(). This commit therefore updates kernel-parameters.txt accordingly. Signed-off-by: Paul E. McKenney --- Documentation/admin-guide/kernel-parameters.txt | 27 +++++++++++++------------ 1 file changed, 14 insertions(+), 13 deletions(-) (limited to 'Documentation/admin-guide') diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt index b0dbb2fa401f..bec49d593583 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -3654,19 +3654,6 @@ latencies, which will choose a value aligned with the appropriate hardware boundaries. - rcutree.jiffies_till_sched_qs= [KNL] - Set required age in jiffies for a - given grace period before RCU starts - soliciting quiescent-state help from - rcu_note_context_switch(). If not specified, the - kernel will calculate a value based on the most - recent settings of rcutree.jiffies_till_first_fqs - and rcutree.jiffies_till_next_fqs. - This calculated value may be viewed in - rcutree.jiffies_to_sched_qs. Any attempt to - set rcutree.jiffies_to_sched_qs will be - cheerfully overwritten. - rcutree.jiffies_till_first_fqs= [KNL] Set delay from grace-period initialization to first attempt to force quiescent states. @@ -3678,6 +3665,20 @@ quiescent states. Units are jiffies, minimum value is one, and maximum value is HZ. + rcutree.jiffies_till_sched_qs= [KNL] + Set required age in jiffies for a + given grace period before RCU starts + soliciting quiescent-state help from + rcu_note_context_switch() and cond_resched(). + If not specified, the kernel will calculate + a value based on the most recent settings + of rcutree.jiffies_till_first_fqs + and rcutree.jiffies_till_next_fqs. + This calculated value may be viewed in + rcutree.jiffies_to_sched_qs. Any attempt to set + rcutree.jiffies_to_sched_qs will be cheerfully + overwritten. + rcutree.kthread_prio= [KNL,BOOT] Set the SCHED_FIFO priority of the RCU per-CPU kthreads (rcuc/N). This value is also used for -- cgit v1.2.3