http2: avoid blocking while holding

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

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

Change-Id: Ibb313424ed2f32c1aeac4645b76aedf227b597a3
Trust: Damien Neil <>
Run-TryBot: Damien Neil <>
TryBot-Result: Go Bot <>
Reviewed-by: Brad Fitzpatrick <>
2 files changed
tree: 5f945e4c914d4b6bdd912dfc2432615d1e5a978e
  1. bpf/
  2. context/
  3. dict/
  4. dns/
  5. html/
  6. http/
  7. http2/
  8. icmp/
  9. idna/
  10. internal/
  11. ipv4/
  12. ipv6/
  13. lif/
  14. nettest/
  15. netutil/
  16. proxy/
  17. publicsuffix/
  18. route/
  19. trace/
  20. webdav/
  21. websocket/
  22. xsrftoken/
  23. .gitattributes
  24. .gitignore
  26. codereview.cfg
  29. go.mod
  30. go.sum

Go Networking

Go Reference

This repository holds supplementary Go networking libraries.


The easiest way to install is to run go get -u You can also manually git clone the repository to $GOPATH/src/

Report Issues / Send Patches

This repository uses Gerrit for code changes. To learn how to submit changes to this repository, see The main issue tracker for the net repository is located at Prefix your issue with “x/net:” in the subject line, so it is easy to find.