[PATCH 0/2] eal: notify secondaries on primary exit

[Stephen Hemminger <stephen@networkplumber.org>]

Bugzilla 1942: when a primary process exits cleanly, secondary
processes other than testpmd do not get notified.  The notification
mechanism added in 25.11 was placed in testpmd and used
rte_mp_request_sync() with a testpmd-specific action name, so any
non-testpmd secondary (dpdk-dumpcap, dpdk-pdump, dpdk-procinfo, or
out-of-tree consumers) would log "Cannot find action: mp_testpmd"
and the primary would block on the 5 second request timeout.

Putting application-specific IPC actions on a broadcast request path
is the wrong layer.  Notification of primary exit is something every
secondary needs and should come from EAL, not from each application.

Patch 1 reverts the testpmd-side mechanism (commit f96273c8e9d3).
The secondary-side primary alive monitor (enable_primary_monitor)
is preserved and continues to handle detection of primary exit via
the existing alarm-based polling of rte_eal_primary_proc_alive().

Patch 2 adds a generic EAL-level notification.  On primary cleanup,
rte_mp_channel_cleanup() broadcasts an MP_REQ_QUIT message to all
known secondaries via rte_mp_sendmsg().  Secondaries register an
internal action handler that tears down their own MP channel on
receipt.  No new public API; no application changes required for
any secondary, in-tree or out.

This is the minimum fix suitable for backport to 25.11 stable.
It addresses the clean exit case.  The crash case (primary killed
or signaled) continues to be handled by the existing
rte_eal_primary_proc_alive() polling on the secondary side, which
detects the primary's release of the config file lock.

A more complete solution using a connected socket type (SOCK_SEQPACKET)
is planned since that can handle both planned and forced exiting
of the primary.

Tested with testpmd (primary) and dpdk-dumpcap, dpdk-pdump,
dpdk-procinfo (secondaries).


Stephen Hemminger (2):
  Revert "app/testpmd: stop forwarding in secondary process"
  eal: notify secondary on primary exit

 app/test-pmd/testpmd.c           | 103 ++-----------------------------
 lib/eal/common/eal_common_proc.c |  51 ++++++++++++++-
 2 files changed, 53 insertions(+), 101 deletions(-)

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2.53.0