Merge tag 'rcu.2024.07.12a' of git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu

Pull RCU updates from Paul McKenney:

 - Update Tasks RCU and Tasks Rude RCU description in Requirements.rst
   and clarify rcu_assign_pointer() and rcu_dereference() ordering
   properties

 - Add lockdep assertions for RCU readers, limit inline wakeups for
   callback-bypass synchronize_rcu(), add an
   rcutree.nohz_full_patience_delay to reduce nohz_full OS jitter, add
   Uladzislau Rezki as RCU maintainer, and fix a subtle
   callback-migration memory-ordering issue

 - Remove a number of redundant memory barriers

 - Remove unnecessary bypass-list lock-contention mitigation, use
   parking API instead of open-coded ad-hoc equivalent, and upgrade
   obsolete comments

 - Revert avoidance of a deadlock that can no longer occur and properly
   synchronize Tasks Trace RCU checking of runqueues

 - Add tests for handling of double-call_rcu() bug, add missing
   MODULE_DESCRIPTION, and add a script that histograms the number of
   calls to RCU updaters

 - Fill out SRCU polled-grace-period API

* tag 'rcu.2024.07.12a' of git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu: (29 commits)
  rcu: Fix rcu_barrier() VS post CPUHP_TEARDOWN_CPU invocation
  rcu: Eliminate lockless accesses to rcu_sync->gp_count
  MAINTAINERS: Add Uladzislau Rezki as RCU maintainer
  rcu: Add rcutree.nohz_full_patience_delay to reduce nohz_full OS jitter
  rcu/exp: Remove redundant full memory barrier at the end of GP
  rcu: Remove full memory barrier on RCU stall printout
  rcu: Remove full memory barrier on boot time eqs sanity check
  rcu/exp: Remove superfluous full memory barrier upon first EQS snapshot
  rcu: Remove superfluous full memory barrier upon first EQS snapshot
  rcu: Remove full ordering on second EQS snapshot
  srcu: Fill out polled grace-period APIs
  srcu: Update cleanup_srcu_struct() comment
  srcu: Add NUM_ACTIVE_SRCU_POLL_OLDSTATE
  srcu: Disable interrupts directly in srcu_gp_end()
  rcu: Disable interrupts directly in rcu_gp_init()
  rcu/tree: Reduce wake up for synchronize_rcu() common case
  rcu/tasks: Fix stale task snaphot for Tasks Trace
  tools/rcu: Add rcu-updaters.sh script
  rcutorture: Add missing MODULE_DESCRIPTION() macros
  rcutorture: Fix rcu_torture_fwd_cb_cr() data race
  ...

1 files changed, 52 insertions, 0 deletions

diff --git a/tools/rcu/rcu-updaters.sh b/tools/rcu/rcu-updaters.sh
new file mode 100755
index 000000000000..4ef1397927bb
--- /dev/null
+++ b/tools/rcu/rcu-updaters.sh
@@ -0,0 +1,52 @@
+#!/bin/sh
+# SPDX-License-Identifier: GPL-2.0+
+#
+# Run bpftrace to obtain a histogram of the types of primitives used to
+# initiate RCU grace periods.  The count associated with rcu_gp_init()
+# is the number of normal (non-expedited) grace periods.
+#
+# Usage: rcu-updaters.sh [ duration-in-seconds ]
+#
+# Note that not all kernel builds have all of these functions.  In those
+# that do not, this script will issue a diagnostic for each that is not
+# found, but continue normally for the rest of the functions.
+
+duration=${1}
+if test -n "${duration}"
+then
+	exitclause='interval:s:'"${duration}"' { exit(); }'
+else
+	echo 'Hit control-C to end sample and print results.'
+fi
+bpftrace -e 'kprobe:kvfree_call_rcu,
+	     kprobe:call_rcu,
+	     kprobe:call_rcu_tasks,
+	     kprobe:call_rcu_tasks_rude,
+	     kprobe:call_rcu_tasks_trace,
+	     kprobe:call_srcu,
+	     kprobe:rcu_barrier,
+	     kprobe:rcu_barrier_tasks,
+	     kprobe:rcu_barrier_tasks_rude,
+	     kprobe:rcu_barrier_tasks_trace,
+	     kprobe:srcu_barrier,
+	     kprobe:synchronize_rcu,
+	     kprobe:synchronize_rcu_expedited,
+	     kprobe:synchronize_rcu_tasks,
+	     kprobe:synchronize_rcu_tasks_rude,
+	     kprobe:synchronize_rcu_tasks_trace,
+	     kprobe:synchronize_srcu,
+	     kprobe:synchronize_srcu_expedited,
+	     kprobe:get_state_synchronize_rcu,
+	     kprobe:get_state_synchronize_rcu_full,
+	     kprobe:start_poll_synchronize_rcu,
+	     kprobe:start_poll_synchronize_rcu_expedited,
+	     kprobe:start_poll_synchronize_rcu_full,
+	     kprobe:start_poll_synchronize_rcu_expedited_full,
+	     kprobe:poll_state_synchronize_rcu,
+	     kprobe:poll_state_synchronize_rcu_full,
+	     kprobe:cond_synchronize_rcu,
+	     kprobe:cond_synchronize_rcu_full,
+	     kprobe:start_poll_synchronize_srcu,
+	     kprobe:poll_state_synchronize_srcu,
+	     kprobe:rcu_gp_init
+	     	{ @counts[func] = count(); } '"${exitclause}"