Verified glibc 2.31-0ubuntu9.3 on Focal. root@ff-lp1912652:~# gcc -O2 -o a.out a.c -lpthread -DITER=1000 -DTHREADS=64 root@ff-lp1912652:~# time ./a.out thread 0: min=128, max=390014464, average=15175.931641, mutexes_locked=224170, flips=12 ... thread 63: min=128, max=212314560, average=31851.539062, mutexes_locked=105648, flips=1 server: min=128, max=249241888, average=581391.875000, mutexes_locked=6158, flips=1000 real 0m0.938s user 0m7.363s sys 0m0.064s root@ff-lp1912652:~# apt install libc6-lse Reading package lists... Done Building dependency tree Reading state information... Done The following NEW packages will be installed: libc6-lse 0 upgraded, 1 newly installed, 0 to remove and 0 not upgraded. Need to get 1035 kB of archives. After this operation, 3244 kB of additional disk space will be used. Get:1 http://ports.ubuntu.com/ubuntu-ports focal-updates/main arm64 libc6-lse arm64 2.31-0ubuntu9.2 [1035 kB] Fetched 1035 kB in 1s (1393 kB/s) Selecting previously unselected package libc6-lse:arm64. (Reading database ... 35769 files and directories currently installed.) Preparing to unpack .../libc6-lse_2.31-0ubuntu9.2_arm64.deb ... Unpacking libc6-lse:arm64 (2.31-0ubuntu9.2) ... Setting up libc6-lse:arm64 (2.31-0ubuntu9.2) ... Processing triggers for libc-bin (2.31-0ubuntu9.2) ... root@ff-lp1912652:~# reboot Session terminated, killing shell... ...killed. ubuntu@ip-172-31-20-158:~$ lxc shell ff-lp1912652 root@ff-lp1912652:~# time ./a.out thread 0: min=128, max=1119296, average=20925.992188, mutexes_locked=1371, flips=36 ...thread 61: min=128, max=15716704, average=295146.343750, mutexes_locked=96, flips=0 thread 62: min=1000000, max=12458848, average=12458848.000000, mutexes_locked=1, flips=0 thread 63: min=128, max=9601760, average=27332.921875, mutexes_locked=1255, flips=9 server: min=128, max=5040224, average=19802.298828, mutexes_locked=1437, flips=1000 real 0m0.014s user 0m0.023s sys 0m0.059s root@ff-lp1912652:~# apt install libc-bin libc-dev-bin libc6 libc6-dev locales Reading package lists... Done Building dependency tree Reading state information... Done Suggested packages: glibc-doc The following packages will be REMOVED: libc6-lse The following packages will be upgraded: libc-bin libc-dev-bin libc6 libc6-dev locales 5 upgraded, 0 newly installed, 1 to remove and 12 not upgraded. Need to get 8770 kB of archives. After this operation, 3159 kB disk space will be freed. Do you want to continue? [Y/n] Get:1 http://ports.ubuntu.com/ubuntu-ports focal-proposed/main arm64 libc6-dev arm64 2.31-0ubuntu9.3 [2068 kB] Get:2 http://ports.ubuntu.com/ubuntu-ports focal-proposed/main arm64 libc-dev-bin arm64 2.31-0ubuntu9.3 [64.2 kB] Get:3 http://ports.ubuntu.com/ubuntu-ports focal-proposed/main arm64 libc6 arm64 2.31-0ubuntu9.3 [2270 kB] Get:4 http://ports.ubuntu.com/ubuntu-ports focal-proposed/main arm64 locales all 2.31-0ubuntu9.3 [3862 kB] Get:5 http://ports.ubuntu.com/ubuntu-ports focal-proposed/main arm64 libc-bin arm64 2.31-0ubuntu9.3 [506 kB] Fetched 8770 kB in 1s (7065 kB/s) Preconfiguring packages ... (Reading database ... 35813 files and directories currently installed.) Removing libc6-lse:arm64 (2.31-0ubuntu9.2) ... (Reading database ... 35769 files and directories currently installed.) Preparing to unpack .../libc6-dev_2.31-0ubuntu9.3_arm64.deb ... Unpacking libc6-dev:arm64 (2.31-0ubuntu9.3) over (2.31-0ubuntu9.2) ... Preparing to unpack .../libc-dev-bin_2.31-0ubuntu9.3_arm64.deb ... Unpacking libc-dev-bin (2.31-0ubuntu9.3) over (2.31-0ubuntu9.2) ... Preparing to unpack .../libc6_2.31-0ubuntu9.3_arm64.deb ... Unpacking libc6:arm64 (2.31-0ubuntu9.3) over (2.31-0ubuntu9.2) ... Setting up libc6:arm64 (2.31-0ubuntu9.3) ... (Reading database ... 35769 files and directories currently installed.) Preparing to unpack .../locales_2.31-0ubuntu9.3_all.deb ... Unpacking locales (2.31-0ubuntu9.3) over (2.31-0ubuntu9.2) ... Preparing to unpack .../libc-bin_2.31-0ubuntu9.3_arm64.deb ... Unpacking libc-bin (2.31-0ubuntu9.3) over (2.31-0ubuntu9.2) ... Setting up libc-bin (2.31-0ubuntu9.3) ... Setting up locales (2.31-0ubuntu9.3) ... Generating locales (this might take a while)... en_US.UTF-8... done Generation complete. Setting up libc-dev-bin (2.31-0ubuntu9.3) ... Setting up libc6-dev:arm64 (2.31-0ubuntu9.3) ... Processing triggers for man-db (2.9.1-1) ... root@ff-lp1912652:~# time ./a.out thread 0: min=128, max=2640064, average=19436.712891, mutexes_locked=1334, flips=31 thread 1: min=128, max=2480992, average=13251.751953, mutexes_locked=2115, flips=53 ... thread 62: min=128, max=112618720, average=94604.898438, mutexes_locked=2004, flips=25 thread 63: min=128, max=129409344, average=88098.539062, mutexes_locked=3266, flips=14 server: min=128, max=94762112, average=140166.890625, mutexes_locked=1347, flips=1000 real 0m0.080s user 0m0.181s sys 0m0.441s root@ff-lp1912652:~# dpkg -l libc6 Desired=Unknown/Install/Remove/Purge/Hold | Status=Not/Inst/Conf-files/Unpacked/halF-conf/Half-inst/trig-aWait/Trig-pend |/ Err?=(none)/Reinst-required (Status,Err: uppercase=bad) ||/ Name Version Architecture Description +++-==============-===============-============-================================= ii libc6:arm64 2.31-0ubuntu9.3 arm64 GNU C Library: Shared libraries root@ff-lp1912652:~#