code review 62180043: gosshnew/ssh: in channel, separate mutexes for reading (flow

gosshnew/ssh: in channel, separate mutexes for reading (flow
control window) and writing (sentClose, access to
writePacket).

With a shared mutex, packetWrite() will block holding the lock
if a key exchange is requested.  This prevents the mux read
loop from making progress. This prevents us from receiving the
other side's kexInit packet, so the writer is never unblocked.

[hanwen-google, 2014-02-12 16:13:56]

Hello agl1, dfc, jpsugar@google.com (cc: agl@golang.org, dave@cheney.net,
golang-codereviews@googlegroups.com, hanwen@google.com, jpsugar@google.com),

I'd like you to review this change to
https://hanwen%40google.com@code.google.com/p/gosshnew/

[agl1, 2014-02-12 17:17:16]

LGTM

https://codereview.appspot.com/62180043/diff/20001/ssh/channel.go
File ssh/channel.go (right):

https://codereview.appspot.com/62180043/diff/20001/ssh/channel.go#newcode177
ssh/channel.go:177: // windowMu protects the flow-control window.
No harm in being explicit:

// windowMu protects myWindow, the flow-control window.

[hanwen-google, 2014-02-12 17:25:23]

https://codereview.appspot.com/62180043/diff/20001/ssh/channel.go
File ssh/channel.go (right):

https://codereview.appspot.com/62180043/diff/20001/ssh/channel.go#newcode177
ssh/channel.go:177: // windowMu protects the flow-control window.
On 2014/02/12 17:17:17, agl1 wrote:
> No harm in being explicit:
> 
> // windowMu protects myWindow, the flow-control window.

Done.

[hanwen-google, 2014-02-12 17:26:02]

*** Submitted as https://code.google.com/p/gosshnew/source/detail?r=470f4cb502d2
***

gosshnew/ssh: in channel, separate mutexes for reading (flow
control window) and writing (sentClose, access to
writePacket).

With a shared mutex, packetWrite() will block holding the lock
if a key exchange is requested.  This prevents the mux read
loop from making progress. This prevents us from receiving the
other side's kexInit packet, so the writer is never unblocked.

R=agl, dave, jpsugar
CC=agl, dave, golang-codereviews, hanwen, jpsugar
https://codereview.appspot.com/62180043