tree 5be86c364374a4ed398981ff87993ae4bcbbadc9
parent 1899dbf7e01c3f05d51ad4e48fd6087094550d4d
author Willy Tarreau <w@1wt.eu> 1575997924 +0100
committer Willy Tarreau <w@1wt.eu> 1576002148 +0100
encoding latin1

BUG/MEDIUM: proto_udp/threads: recv() and send() must not be exclusive.

This is a complement to previous fix for bug #399. The exclusion between
the recv() and send() calls prevents send handlers from being called if
rx readiness is reported. The DNS code can trigger this situations with
threads where the fd_recv_ready() flag disappears between the test in
dgram_fd_handler() and the second test in dns_resolve_recv() while a
thread calls fd_cant_recv(), and this situation can sustain itself for
a while. With 8 threads and an error in the socket queue, placing a
printf on the return statement in dns_resolve_recv() scrolls very fast.

Simply removing the "else" in dgram_fd_handler() addresses the issue.

This fix must be backported as far as 1.6.

(cherry picked from commit d7f76a0a50f4ac6b32d2317c675b3752133ef6d2)
Signed-off-by: Willy Tarreau <w@1wt.eu>
(cherry picked from commit 8e4a62508c4e2f6ba0ae01f552a13208a8018875)
Signed-off-by: Willy Tarreau <w@1wt.eu>