tree 2c0293c9cffd22ad26d7f82fe32d0d15cc0b9d8b
parent 27c754cd2479adc5dbffce5a0d827606a21ea063
author Olivier Houchard <ohouchard@haproxy.com> 1562852940 +0200
committer Christopher Faulet <cfaulet@haproxy.com> 1562918932 +0200

BUG/MEDIUM: servers: Fix a race condition with idle connections.

When we're purging idle connections, there's a race condition, when we're
removing the connection from the idle list, to add it to the list of
connections to free, if the thread owning the connection tries to free it
at the same time.
To fix this, simply add a per-thread lock, that has to be hold before
removing the connection from the idle list, and when, in conn_free(), we're
about to remove the connection from every list. That way, we know for sure
the connection will stay valid while we remove it from the idle list, to add
it to the list of connections to free.
This should happen rarely enough that it shouldn't have any impact on
performances.
This has not been reported yet, but could provoke random segfaults.

This should be backported to 2.0.

(cherry picked from commit 4be7190c1024b82248a55456ea44b40c40d4f066)
Signed-off-by: Christopher Faulet <cfaulet@haproxy.com>