tree 1faca9cc0effe406091c7108ad47dbf9acd1f62d
parent 041787280976d0bad15c646fc7c7bbfef76d7ee5
author Austin Clements <austin@google.com> 1447957603 -0500
committer Austin Clements <austin@google.com> 1448305995 +0000

runtime: make stack barrier locking more robust

The stack barrier locking functions use a simple cas lock because they
need to support trylock, but currently don't increment g.m.locks. This
is okay right now because they always run on the system stack or the
signal stack and are hence non-preemtible, but this could lead to
difficult-to-reproduce deadlocks if these conditions change in the
future.

Make these functions more robust by incrementing g.m.locks and making
them nosplit to enforce non-preemtibility.

Change-Id: I73d60a35bd2ad2d81c73aeb20dbd37665730eb1b
Reviewed-on: https://go-review.googlesource.com/17058
Run-TryBot: Austin Clements <austin@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ingo Oeser <nightlyone@googlemail.com>
Reviewed-by: Russ Cox <rsc@golang.org>