code review 4203042: runtime: pass to signal handler value of g at time of signal

runtime: pass to signal handler value of g at time of signal

The existing code assumed that signals only arrived
while executing on the goroutine stack (g == m->curg),
not while executing on the scheduler stack (g == m->g0).

Most of the signal handling trampolines correctly saved
and restored g already, but the sighandler C code did not
have access to it.

Some rewriting of assembly to make the various
implementations as similar as possible.

Will need to change Windows too but I don't
understand how sigtramp gets called there.

[rsc, 2011-02-23 04:51:12]

Hello r (cc: golang-dev@googlegroups.com),

I'd like you to review this change to
https://go.googlecode.com/hg/

[rsc, 2011-02-23 04:51:54]

Only tested linux/amd64.  Will test the other linux
and darwin ports tomorrow.

[r, 2011-02-23 04:59:23]

LGTM but i'm hardly in a position of confidence when it comes to unix signal
handlers vs. assembly

[rsc, 2011-02-23 19:47:45]

*** Submitted as 9fb768bbf24f ***

runtime: pass to signal handler value of g at time of signal

The existing code assumed that signals only arrived
while executing on the goroutine stack (g == m->curg),
not while executing on the scheduler stack (g == m->g0).

Most of the signal handling trampolines correctly saved
and restored g already, but the sighandler C code did not
have access to it.

Some rewriting of assembly to make the various
implementations as similar as possible.

Will need to change Windows too but I don't
understand how sigtramp gets called there.

R=r
CC=golang-dev
http://codereview.appspot.com/4203042