From a5bde5d8fde8a8cb28e59a672d5ddc5b9c1e7656 Mon Sep 17 00:00:00 2001 From: Breno Leitao Date: Wed, 5 Aug 2026 07:52:36 -0700 Subject: workqueue: skip the node_nr_active update for non-unbound workqueues apply_wqattrs_commit() updates node_nr_active->max unconditionally. wq->node_nr_active[] is only allocated for unbound workqueues, so guard the call before per-cpu workqueues start using this path. No functional change: only unbound workqueues reach apply_wqattrs_*() today. Signed-off-by: Breno Leitao Signed-off-by: Tejun Heo --- Documentation/kbuild/Kconfig.recursion-issue-01 | 57 +++++++++++++++++++++++++ 1 file changed, 57 insertions(+) create mode 100644 Documentation/kbuild/Kconfig.recursion-issue-01 (limited to 'Documentation/kbuild/Kconfig.recursion-issue-01') diff --git a/Documentation/kbuild/Kconfig.recursion-issue-01 b/Documentation/kbuild/Kconfig.recursion-issue-01 new file mode 100644 index 000000000..ac49836d8 --- /dev/null +++ b/Documentation/kbuild/Kconfig.recursion-issue-01 @@ -0,0 +1,57 @@ +# Simple Kconfig recursive issue +# ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ +# +# Test with: +# +# make KBUILD_KCONFIG=Documentation/kbuild/Kconfig.recursion-issue-01 allnoconfig +# +# This Kconfig file has a simple recursive dependency issue. In order to +# understand why this recursive dependency issue occurs lets consider what +# Kconfig needs to address. We iterate over what Kconfig needs to address +# by stepping through the questions it needs to address sequentially. +# +# * What values are possible for CORE? +# +# CORE_BELL_A_ADVANCED selects CORE, which means that it influences the values +# that are possible for CORE. So for example if CORE_BELL_A_ADVANCED is 'y', +# CORE must be 'y' too. +# +# * What influences CORE_BELL_A_ADVANCED? +# +# As the name implies CORE_BELL_A_ADVANCED is an advanced feature of +# CORE_BELL_A so naturally it depends on CORE_BELL_A. So if CORE_BELL_A is 'y' +# we know CORE_BELL_A_ADVANCED can be 'y' too. +# +# * What influences CORE_BELL_A? +# +# CORE_BELL_A depends on CORE, so CORE influences CORE_BELL_A. +# +# But that is a problem, because this means that in order to determine +# what values are possible for CORE we ended up needing to address questions +# regarding possible values of CORE itself again. Answering the original +# question of what are the possible values of CORE would make the kconfig +# tools run in a loop. When this happens Kconfig exits and complains about +# the "recursive dependency detected" error. +# +# Reading the Documentation/kbuild/Kconfig.recursion-issue-01 file it may be +# obvious that an easy solution to this problem should just be the removal +# of the "select CORE" from CORE_BELL_A_ADVANCED as that is implicit already +# since CORE_BELL_A depends on CORE. Recursive dependency issues are not always +# so trivial to resolve, we provide another example below of practical +# implications of this recursive issue where the solution is perhaps not so +# easy to understand. Note that matching semantics on the dependency on +# CORE also consist of a solution to this recursive problem. + +mainmenu "Simple example to demo kconfig recursive dependency issue" + +config CORE + tristate + +config CORE_BELL_A + tristate + depends on CORE + +config CORE_BELL_A_ADVANCED + tristate + depends on CORE_BELL_A + select CORE -- cgit v1.3.1