commit 978cfadd31cf6299758dbb5165d451ce91989f1a
author Damien Neil <dneil@google.com> Sat Sep 11 18:41:19 2021 -0700
committer Damien Neil <dneil@google.com> Fri Sep 17 22:17:30 2021 +0000
tree 5f945e4c914d4b6bdd912dfc2432615d1e5a978e
parent 95888ee714434b81cb02e8f657fb798b0185a95c

http2: avoid blocking while holding ClientConn.mu

Operations which examine the state of a ClientConn--notably,
the connection pool's check to see if a conn is available to
take a new request--need to acquire mu. Blocking while holding mu,
such as when writing to the network, blocks these operations.

Remove blocking operations from the mutex.
Perform network writes with only ClientConn.wmu held.
Clarify that wmu guards the per-conn HPACK encoder and buffer.

Add a new mutex guarding request creation, covering the critical
section starting with allocating a new stream ID and continuing
until the stream is created.

Fix a locking issue where trailers were written from the HPACK
buffer with only wmu held, but headers were encoded into the buffer
with only mu held. (Now both encoding and writes occur with wmu
held.)

Fixes golang/go#32388.
Fixes golang/go#48340.

Change-Id: Ibb313424ed2f32c1aeac4645b76aedf227b597a3
Reviewed-on: https://go-review.googlesource.com/c/net/+/349594
Trust: Damien Neil <dneil@google.com>
Run-TryBot: Damien Neil <dneil@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>