Re: [PATCH v2] Revert "eal/unix: fix thread creation"

[David Marchand <david.marchand@redhat.com>]

Hello Luca,

>
> This commit introduced a regression on arm64, causing a deadlock.
> lcores_autotest gets stuck and never terminates:
>
> [ 1077s] EAL: Detected CPU lcores: 4
> [ 1077s] EAL: Detected NUMA nodes: 1
> [ 1077s] EAL: Detected shared linkage of DPDK
> [ 1077s] EAL: Multi-process socket /tmp/dpdk/rte/mp_socket
> [ 1077s] EAL: Selected IOVA mode 'VA'
> [ 1077s] APP: HPET is not enabled, using TSC as default timer
> [ 1077s] RTE>>lcores_autotest
> [ 1127s] DPDK:fast-tests / lcores_autotest time out (After 50.0 seconds)
>
> This is 100% reproducible when running the fast tests suite
> after a package build on OBS. Reverting it reliably fixes the
> issue.
>
> This reverts commit b28c6196b132d1f25cb8c1bf781520fc41556b3a.
>
> Signed-off-by: Luca Boccassi <luca.boccassi@gmail.com>
> ---
> v2: add forgotten signed-off-by
>
> I have bisected this long standing issue and identified the commit
> that introduced it. If anybody can provide a different fix that would
> be better, but if it's not possible to find another solution, it would
> be good to revert it until it can be found, to resolve the regression.

Thanks for tracking this down.

There is one issue with reverting: iirc, it reintroduces a race / double-free.

Could you share a backtrace when hitting this deadlock?

On my side, I am not able to catch it neither on x86 nor in a ARM vm I borrowed.

I built dpdk manually in a Debian 12 container, trying to mimick OBS
cflags & friends.
# rm -rf build-debian; CC='ccache gcc' meson setup build-debian
-Dmachine=default -Dbuildtype=plain -Ddefault_library=shared
-Dc_args='-O2 -fstack-protector-strong -Wformat
-Werror=format-security -Werror -Wdate-time -D_FORTIFY_SOURCE=2' &&
ninja -C build-debian && meson test -C build-debian --suite fast-tests
--verbose -t 5
...
36/81 DPDK:fast-tests / lcores_autotest             RUNNING
>>> LD_LIBRARY_PATH=/root/dpdk/build-debian/lib:/root/dpdk/build-debian/drivers MALLOC_PERTURB_=90 DPDK_TEST=lcores_autotest /root/dpdk/build-debian/app/dpdk-test --no-huge -m 2048 -d /root/dpdk/build-debian/drivers
――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――
✀  ――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――
EAL: Detected CPU lcores: 3
EAL: Detected NUMA nodes: 1
EAL: Detected shared linkage of DPDK
EAL: Multi-process socket /var/run/dpdk/rte/mp_socket
EAL: Selected IOVA mode 'VA'
VIRTIO_INIT: eth_virtio_pci_init(): Failed to init PCI device
PCI_BUS: Requested device 0000:01:00.0 cannot be used
APP: HPET is not enabled, using TSC as default timer
RTE>>lcores_autotest
EAL threads count: 3, RTE_MAX_LCORE=256
lcore 0, socket 0, role RTE, cpuset 0
lcore 1, socket 0, role RTE, cpuset 1
lcore 2, socket 0, role RTE, cpuset 2
non-EAL threads count: 253
Warning: could not register new thread (this might be expected during
this test), reason Cannot allocate memory
non-EAL threads count: 254
Warning: could not register new thread (this might be expected during
this test), reason Cannot allocate memory
lcore 0, socket 0, role RTE, cpuset 0
lcore 1, socket 0, role RTE, cpuset 1
lcore 2, socket 0, role RTE, cpuset 2
lcore 3, socket 0, role NON_EAL, cpuset 0
lcore 0, socket 0, role RTE, cpuset 0
lcore 1, socket 0, role RTE, cpuset 1
lcore 2, socket 0, role RTE, cpuset 2
Control thread running successfully
Test OK
RTE>>――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――
36/81 DPDK:fast-tests / lcores_autotest             OK              1.87s



This vm runs on:
# lspcu
Architecture:             aarch64
  CPU op-mode(s):         32-bit, 64-bit
  Byte Order:             Little Endian
CPU(s):                   3
  On-line CPU(s) list:    0-2
Vendor ID:                ARM
  BIOS Vendor ID:         QEMU
  Model name:             Neoverse-N1
    BIOS Model name:      virt-rhel8.6.0  CPU @ 2.0GHz
...


-- 
David Marchand