From: Olivier Dion <odion@efficios.com>
Date: Tue, 14 Feb 2023 19:35:34 +0000 (-0500)
Subject: Fix: Wrong assumption about possible CPUs
X-Git-Tag: v2.12.14~4
X-Git-Url: https://git.lttng.org./?a=commitdiff_plain;h=f33e65faf5e4ffa7d249f58bf6dbdaf2bcb28693;p=lttng-tools.git

Fix: Wrong assumption about possible CPUs

cpuset is not necessary contiguous.  Thus, we need to parse
/sys/devices/system/cpu/posssible correctly.

Also, the `get_exposed_cpus_list' utility functions is required for
taskset-ting on the correct CPUs available to the test environment.

Change-Id: I062ce8d311ff0e8c4b757fe6f36387e3007cfa27
Signed-off-by: Olivier Dion <odion@efficios.com>
Signed-off-by: Jérémie Galarneau <jeremie.galarneau@efficios.com>
---

diff --git a/tests/regression/tools/snapshots/ust_test b/tests/regression/tools/snapshots/ust_test
index e6a463bce..24f43aec6 100755
--- a/tests/regression/tools/snapshots/ust_test
+++ b/tests/regression/tools/snapshots/ust_test
@@ -298,14 +298,15 @@ function test_ust_local_snapshot_small_overwrite_buffers ()
 function test_ust_local_snapshot_max_size ()
 {
 	local possible_cpus
-	local online_cpus
+	local cpus_list
 	local subbuf_size
 	local subbuf_count
 	local snapshot_max_size
 	local channel_max_size_per_cpu
 
+	IFS=" " read -r -a cpus_list <<< "$(get_exposed_cpus_list)"
+
 	possible_cpus=$(get_possible_cpus_count)
-	online_cpus=$(conf_proc_count)
 	subbuf_size=$(getconf PAGE_SIZE)
 	subbuf_count=8
 	snapshot_max_size=$((subbuf_size*possible_cpus))
@@ -325,9 +326,10 @@ function test_ust_local_snapshot_max_size ()
 
 	# Fill all ring-buffers of the channel; assuming event size of at least one
 	# byte
-	for cpu in $(seq "$online_cpus");
+	for cpu in "${cpus_list[@]}";
 	do
-		taskset --cpu-list $((cpu-1)) "$TESTAPP_BIN" \
+		diag "setting affinity to $cpu"
+		taskset --cpu-list "$cpu" "$TESTAPP_BIN" \
 			--iter "$channel_max_size_per_cpu"
 	done
 	diag "Filled channel ring-buffers"
diff --git a/tests/utils/utils.sh b/tests/utils/utils.sh
index c9907fd6d..09c4ae28d 100644
--- a/tests/utils/utils.sh
+++ b/tests/utils/utils.sh
@@ -133,33 +133,69 @@ function randstring()
 # Helpers for get_possible_cpus.
 function get_possible_cpus_count_from_sysfs_possible_mask()
 {
-	local max_possible_cpu_id=$(cut -d '-' -f 2 < /sys/devices/system/cpu/possible)
-	echo $((max_possible_cpu_id+1))
+	local max_possible_cpu_id
+
+	# The Awk script extracts the highest CPU id from the possible CPU
+	# mask. Assuming a numerical order, a field separator '-' and a record
+	# separator ','. The last value parsed is the highest id.
+	if [ -f /sys/devices/system/cpu/possible ]; then
+		max_possible_cpu_id=$(awk -F '-' 'BEGIN { RS = ","} { last = $NF } END { printf("%d\n", last) }' \
+				      /sys/devices/system/cpu/possible)
+		echo "$((max_possible_cpu_id+1))"
+	else
+		echo "0"
+	fi
 }
 
+# This is a fallback if the possible CPU mask is not available. This will not
+# take into account unplugged CPUs.
 function get_max_cpus_count_from_sysfs_cpu_directories()
 {
-	local max_possible_cpu_id= \
-		$(find /sys/devices/system/cpu/ -mindepth 1 -maxdepth 1 -regex ".+cpu[0-9]+" | \
-		  sed -e 's/cpu//g' | \
-		  awk -F '/' '{ if ($NF > N) N = $NF } END { print N }')
-	echo $((max_possible_cpu_id+1))
+	local max_possible_cpu_id=0
+	local current_cpu_id
+
+	for i in /sys/devices/system/cpu/cpu[0-9]*; do
+		current_cpu_id="${i#/sys/devices/system/cpu/cpu}"
+		if [ "$current_cpu_id" -gt "$max_possible_cpu_id" ]; then
+			max_possible_cpu_id="$current_cpu_id"
+		fi
+	done
+
+	echo "$((max_possible_cpu_id+1))"
 }
 
 # Return the number of possible CPUs.
 function get_possible_cpus_count()
 {
-	local possible_cpus_count=$(get_possible_cpus_count_from_sysfs_possible_mask)
+	local possible_cpus_count
+	possible_cpus_count=$(get_possible_cpus_count_from_sysfs_possible_mask)
 
-	if [ $? -ne 0 ]; then
+	if [ "$possible_cpus_count" -eq "0" ]; then
+		local configured_cpus_count
+		configured_cpus_count=$(getconf _NPROCESSORS_CONF)
 		possible_cpus_count=$(get_max_cpus_count_from_sysfs_cpu_directories)
-		local configured_cpus_count=$(getconf _NPROCESSORS_CONF)
-		possible_cpus_count=$(($configured_cpus_count > $possible_cpus_count \
-							      ? $configured_cpus_count \
-							      : $possible_cpus_count))
+		possible_cpus_count=$((configured_cpus_count > possible_cpus_count \
+							     ? configured_cpus_count \
+							     : possible_cpus_count))
 	fi
 
-	echo $possible_cpus_count
+	echo "$possible_cpus_count"
+}
+
+# Return the list of exposed CPU.
+#
+# NOTE! Use it like so:
+#
+# IFS=" " read -r -a VARIABLE <<< "$(get_exposed_cpus_list)"
+function get_exposed_cpus_list()
+{
+	local list=()
+
+	for i in /sys/devices/system/cpu/cpu[0-9]*; do
+		list+=("${i#/sys/devices/system/cpu/cpu}")
+	done
+
+	echo "${list[@]}"
 }
 
 # Return the number of _configured_ CPUs.