tree 7dbd58d1340fbcd9f9d494c3233de952421cd51a
parent f11be0ea1e8e571234cb41a2fcdde2cf2161df37
author Willy Tarreau <w@1wt.eu> 1578665817 +0100
committer Willy Tarreau <w@1wt.eu> 1579282236 +0100
encoding latin1

MEDIUM: mux-h2: do not make an h2s subscribe to itself on deferred shut

The logic handling the deferred shutdown is a bit complex because it
involves a wait_event struct in each h2s dedicated to subscribing to
itself when shutdowns are not immediately possible. This implies that
we will not be able to support a shutdown and a receive subscription
in the future when we merge all wait events.

Let's solely rely on the H2_SF_WANT_SHUT_{R,W} flags instead and have
an autonomous tasklet for this. This requires to add a few controls
in the code because now when waking up a stream we need to check if it
is for I/O or just a shut, but since sending and shutting are exclusive
it's not difficult.

One point worth noting is that further resources could be shaved off
by only allocating the tasklet when failing to shut, given that in the
vast majority of streams it will never be used. In fact the sole purpose
of the tasklet is to support calling this code from outside the H2 mux
context. Looking at the code, it seems that not too many adaptations
would be required to have the send_list walking code deal with sending
the shut bits itself and further simplify all this.