cgroup/cpuset: Take isolated CPUs out of workqueue unbound cpumask

To make CPUs in isolated cpuset partition closer in isolation to
the boot time isolated CPUs specified in the "isolcpus" boot command
line option, we need to take those CPUs out of the workqueue unbound
cpumask so that work functions from the unbound workqueues won't run
on those CPUs.  Otherwise, they will interfere the user tasks running
on those isolated CPUs.

With the introduction of the workqueue_unbound_exclude_cpumask() helper
function in an earlier commit, those isolated CPUs can now be taken
out from the workqueue unbound cpumask.

This patch also updates cgroup-v2.rst to mention that isolated
CPUs will be excluded from unbound workqueue cpumask as well as
updating test_cpuset_prs.sh to verify the correctness of the new
*cpuset.cpus.isolated file, if available via cgroup_debug option.

Signed-off-by: Waiman Long <longman@redhat.com>
Signed-off-by: Tejun Heo <tj@kernel.org>

1 files changed, 65 insertions, 9 deletions

diff --git a/tools/testing/selftests/cgroup/test_cpuset_prs.sh b/tools/testing/selftests/cgroup/test_cpuset_prs.sh
index 2b825019f806..7b7c4c2b6d85 100755
--- a/tools/testing/selftests/cgroup/test_cpuset_prs.sh
+++ b/tools/testing/selftests/cgroup/test_cpuset_prs.sh
@@ -232,11 +232,11 @@ TEST_MATRIX=(
 	" C0-3:S+ C1-3:S+ C2-3   C4-5   X2-3  X2-3:P1   P2     P1    0 A1:0-1,A2:,A3:2-3,B1:4-5 \
 								       A1:P0,A2:P1,A3:P2,B1:P1 2-3"
 	" C0-3:S+ C1-3:S+ C2-3    C4    X2-3  X2-3:P1   P2     P1    0 A1:0-1,A2:,A3:2-3,B1:4 \
-								       A1:P0,A2:P1,A3:P2,B1:P1 2-4"
+								       A1:P0,A2:P1,A3:P2,B1:P1 2-4,2-3"
 	" C0-3:S+ C1-3:S+  C3     C4    X2-3  X2-3:P1   P2     P1    0 A1:0-1,A2:2,A3:3,B1:4 \
-								       A1:P0,A2:P1,A3:P2,B1:P1 2-4"
+								       A1:P0,A2:P1,A3:P2,B1:P1 2-4,3"
 	" C0-4:S+ C1-4:S+ C2-4     .    X2-4  X2-4:P2  X4:P1    .    0 A1:0-1,A2:2-3,A3:4 \
-								       A1:P0,A2:P2,A3:P1 2-4"
+								       A1:P0,A2:P2,A3:P1 2-4,2-3"
 	" C0-4:X2-4:S+ C1-4:X2-4:S+:P2 C2-4:X4:P1 \
 				   .      .      X5      .      .    0 A1:0-4,A2:1-4,A3:2-4 \
 								       A1:P0,A2:P-2,A3:P-1"
@@ -248,7 +248,7 @@ TEST_MATRIX=(
 	" C0-3:S+ C1-3:S+ C2-3     .    X2-3   X2-3 X2-3:P2:O2=0 .   0 A1:0-1,A2:1,A3:3 A1:P0,A3:P2 2-3"
 	" C0-3:S+ C1-3:S+ C2-3     .    X2-3   X2-3 X2-3:P2:O2=0 O2=1 0 A1:0-1,A2:1,A3:2-3 A1:P0,A3:P2 2-3"
 	" C0-3:S+ C1-3:S+  C3      .    X2-3   X2-3    P2:O3=0   .   0 A1:0-2,A2:1-2,A3: A1:P0,A3:P2 3"
-	" C0-3:S+ C1-3:S+  C3      .    X2-3   X2-3   T:P2:O3=0  .   0 A1:0-2,A2:1-2,A3:1-2 A1:P0,A3:P-2 3"
+	" C0-3:S+ C1-3:S+  C3      .    X2-3   X2-3   T:P2:O3=0  .   0 A1:0-2,A2:1-2,A3:1-2 A1:P0,A3:P-2 3,"
 
 	# An invalidated remote partition cannot self-recover from hotplug
 	" C0-3:S+ C1-3:S+  C2      .    X2-3   X2-3   T:P2:O2=0 O2=1 0 A1:0-3,A2:1-3,A3:2 A1:P0,A3:P-2"
@@ -376,7 +376,7 @@ write_cpu_online()
 		}
 	fi
 	echo $VAL > $CPUFILE
-	pause 0.01
+	pause 0.05
 }
 
 #
@@ -508,12 +508,14 @@ dump_states()
 		XECPUS=$DIR/cpuset.cpus.exclusive.effective
 		PRS=$DIR/cpuset.cpus.partition
 		PCPUS=$DIR/.__DEBUG__.cpuset.cpus.subpartitions
+		ISCPUS=$DIR/.__DEBUG__.cpuset.cpus.isolated
 		[[ -e $CPUS   ]] && echo "$CPUS: $(cat $CPUS)"
 		[[ -e $XCPUS  ]] && echo "$XCPUS: $(cat $XCPUS)"
 		[[ -e $ECPUS  ]] && echo "$ECPUS: $(cat $ECPUS)"
 		[[ -e $XECPUS ]] && echo "$XECPUS: $(cat $XECPUS)"
 		[[ -e $PRS    ]] && echo "$PRS: $(cat $PRS)"
 		[[ -e $PCPUS  ]] && echo "$PCPUS: $(cat $PCPUS)"
+		[[ -e $ISCPUS ]] && echo "$ISCPUS: $(cat $ISCPUS)"
 	done
 }
 
@@ -591,11 +593,17 @@ check_cgroup_states()
 
 #
 # Get isolated (including offline) CPUs by looking at
-# /sys/kernel/debug/sched/domains and compare that with the expected value.
+# /sys/kernel/debug/sched/domains and *cpuset.cpus.isolated control file,
+# if available, and compare that with the expected value.
 #
-# Note that a sched domain of just 1 CPU will be considered isolated.
+# Note that isolated CPUs from the sched/domains context include offline
+# CPUs as well as CPUs in non-isolated 1-CPU partition. Those CPUs may
+# not be included in the *cpuset.cpus.isolated control file which contains
+# only CPUs in isolated partitions.
 #
-# $1 - expected isolated cpu list
+# $1 - expected isolated cpu list(s) <isolcpus1>{,<isolcpus2>}
+# <isolcpus1> - expected sched/domains value
+# <isolcpus2> - *cpuset.cpus.isolated value = <isolcpus1> if not defined
 #
 check_isolcpus()
 {
@@ -603,8 +611,38 @@ check_isolcpus()
 	ISOLCPUS=
 	LASTISOLCPU=
 	SCHED_DOMAINS=/sys/kernel/debug/sched/domains
+	ISCPUS=${CGROUP2}/.__DEBUG__.cpuset.cpus.isolated
+	if [[ $EXPECT_VAL = . ]]
+	then
+		EXPECT_VAL=
+		EXPECT_VAL2=
+	elif [[ $(expr $EXPECT_VAL : ".*,.*") > 0 ]]
+	then
+		set -- $(echo $EXPECT_VAL | sed -e "s/,/ /g")
+		EXPECT_VAL=$1
+		EXPECT_VAL2=$2
+	else
+		EXPECT_VAL2=$EXPECT_VAL
+	fi
+
+	#
+	# Check the debug isolated cpumask, if present
+	#
+	[[ -f $ISCPUS ]] && {
+		ISOLCPUS=$(cat $ISCPUS)
+		[[ "$EXPECT_VAL2" != "$ISOLCPUS" ]] && {
+			# Take a 50ms pause and try again
+			pause 0.05
+			ISOLCPUS=$(cat $ISCPUS)
+		}
+		[[ "$EXPECT_VAL2" != "$ISOLCPUS" ]] && return 1
+		ISOLCPUS=
+	}
+
+	#
+	# Use the sched domain in debugfs to check isolated CPUs, if available
+	#
 	[[ -d $SCHED_DOMAINS ]] || return 0
-	[[ $EXPECT_VAL = . ]] && EXPECT_VAL=
 
 	for ((CPU=0; CPU < $NR_CPUS; CPU++))
 	do
@@ -649,6 +687,22 @@ test_fail()
 }
 
 #
+# Check to see if there are unexpected isolated CPUs left
+#
+null_isolcpus_check()
+{
+	[[ $VERBOSE -gt 0 ]] || return 0
+	pause 0.02
+	check_isolcpus "."
+	if [[ $? -ne 0 ]]
+	then
+		echo "Unexpected isolated CPUs: $ISOLCPUS"
+		dump_states
+		exit 1
+	fi
+}
+
+#
 # Run cpuset state transition test
 #  $1 - test matrix name
 #
@@ -733,6 +787,7 @@ run_state_test()
 			echo "Effective cpus changed to $NEWLIST after test $I!"
 			exit 1
 		}
+		null_isolcpus_check
 		[[ $VERBOSE -gt 0 ]] && echo "Test $I done."
 		((I++))
 	done
@@ -802,6 +857,7 @@ test_isolated()
 	console_msg "Cleaning up"
 	echo $$ > $CGROUP2/cgroup.procs
 	[[ -d A1 ]] && rmdir A1
+	null_isolcpus_check
 }
 
 #