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10 Commits

Author SHA1 Message Date
Ian Lance Taylor
872b168fe3 runtime: if we don't handle a signal on a non-Go thread, raise it
In the past badsignal would crash the program.  In
https://golang.org/cl/10757044 badsignal was changed to call sigsend,
to fix issue #3250.  The effect of this was that when a non-Go thread
received a signal, and os/signal.Notify was not being used to check
for occurrences of the signal, the signal was ignored.

This changes the code so that if os/signal.Notify is not being used,
then the signal handler is reset to what it was, and the signal is
raised again.  This lets non-Go threads handle the signal as they
wish.  In particular, it means that a segmentation violation in a
non-Go thread will ordinarily crash the process, as it should.

Fixes #10139.
Update #11794.

Change-Id: I2109444aaada9d963ad03b1d071ec667760515e5
Reviewed-on: https://go-review.googlesource.com/12503
Reviewed-by: Russ Cox <rsc@golang.org>
Run-TryBot: Ian Lance Taylor <iant@golang.org>
2015-07-22 20:26:29 +00:00
Elias Naur
84cfba17c2 runtime: don't always unblock all signals
Ian proposed an improved way of handling signals masks in Go, motivated
by a problem where the Android java runtime expects certain signals to
be blocked for all JVM threads. Discussion here

https://groups.google.com/forum/#!topic/golang-dev/_TSCkQHJt6g

Ian's text is used in the following:

A Go program always needs to have the synchronous signals enabled.
These are the signals for which _SigPanic is set in sigtable, namely
SIGSEGV, SIGBUS, SIGFPE.

A Go program that uses the os/signal package, and calls signal.Notify,
needs to have at least one thread which is not blocking that signal,
but it doesn't matter much which one.

Unix programs do not change signal mask across execve.  They inherit
signal masks across fork.  The shell uses this fact to some extent;
for example, the job control signals (SIGTTIN, SIGTTOU, SIGTSTP) are
blocked for commands run due to backquote quoting or $().

Our current position on signal masks was not thought out.  We wandered
into step by step, e.g., http://golang.org/cl/7323067 .

This CL does the following:

Introduce a new platform hook, msigsave, that saves the signal mask of
the current thread to m.sigsave.

Call msigsave from needm and newm.

In minit grab set up the signal mask from m.sigsave and unblock the
essential synchronous signals, and SIGILL, SIGTRAP, SIGPROF, SIGSTKFLT
(for systems that have it).

In unminit, restore the signal mask from m.sigsave.

The first time that os/signal.Notify is called, start a new thread whose
only purpose is to update its signal mask to make sure signals for
signal.Notify are unblocked on at least one thread.

The effect on Go programs will be that if they are invoked with some
non-synchronous signals blocked, those signals will normally be
ignored.  Previously, those signals would mostly be ignored.  A change
in behaviour will occur for programs started with any of these signals
blocked, if they receive the signal: SIGHUP, SIGINT, SIGQUIT, SIGABRT,
SIGTERM.  Previously those signals would always cause a crash (unless
using the os/signal package); with this change, they will be ignored
if the program is started with the signal blocked (and does not use
the os/signal package).

./all.bash completes successfully on linux/amd64.

OpenBSD is missing the implementation.

Change-Id: I188098ba7eb85eae4c14861269cc466f2aa40e8c
Reviewed-on: https://go-review.googlesource.com/10173
Reviewed-by: Ian Lance Taylor <iant@golang.org>
2015-05-22 20:24:08 +00:00
Austin Clements
9e6f7aac28 runtime: make "write barriers are not allowed" comments more precise
Currently, various functions are marked with the comment

  // May run without a P, so write barriers are not allowed.

However, "running without a P" is ambiguous. We intended these to mean
that m.p may be nil (which is the condition checked by the write
barrier). The comment could also be taken to mean that a
stop-the-world may happen, which is not the case for these functions
because they run in situations where there is in fact a function on
the stack holding a P locally, it just isn't in m.p.

Change these comments to state precisely what we mean, that m.p may be
nil.

Change-Id: I4a4a1d26aebd455e5067540e13b9f96a7482146c
Reviewed-on: https://go-review.googlesource.com/8209
Reviewed-by: Minux Ma <minux@golang.org>
Reviewed-by: Rick Hudson <rlh@golang.org>
2015-03-30 15:13:53 +00:00
Austin Clements
392336f94e runtime: disallow write barriers in handoffp and callees
handoffp by definition runs without a P, so it's not allowed to have
write barriers. It doesn't have any right now, but mark it
nowritebarrier to disallow any creeping in in the future. handoffp in
turns calls startm, newm, and newosproc, all of which are "below Go"
and make sense to run without a P, so disallow write barriers in these
as well.

For most functions, we've done this because they may race with
stoptheworld() and hence must not have write barriers. For these
functions, it's a little different: the world can't stop while we're
in handoffp, so this race isn't present. But we implement this
restriction with a somewhat broader rule that you can't have a write
barrier without a P. We like this rule because it's simple and means
that our write barriers can depend on there being a P, even though
this rule is actually a little broader than necessary. Hence, even
though there's no danger of the race in these functions, we want to
adhere to the broader rule.

Change-Id: Ie22319c30eea37d703eb52f5c7ca5da872030b88
Reviewed-on: https://go-review.googlesource.com/8130
Run-TryBot: Austin Clements <austin@google.com>
Reviewed-by: Minux Ma <minux@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Rick Hudson <rlh@golang.org>
2015-03-26 20:38:59 +00:00
Shenghou Ma
400f58a010 runtime: don't trigger write barrier in newosproc for nacl
This should fix the intermittent calling write barrier with mp.p == nil
failures on the nacl/386 builder.

Change-Id: I34aef5ca75ccd2939e6a6ad3f5dacec64903074e
Signed-off-by: Shenghou Ma <minux@golang.org>
Reviewed-on: https://go-review.googlesource.com/7973
Reviewed-by: Austin Clements <austin@google.com>
2015-03-26 19:58:14 +00:00
Shenghou Ma
003dccfac4 runtime, syscall: use the new get_random_bytes syscall for NaCl
The SecureRandom named service was removed in
https://codereview.chromium.org/550523002. And the new syscall
was introduced in https://codereview.chromium.org/537543003.

Accepting this will remove the support for older version of
sel_ldr. I've confirmed that both pepper_40 and current
pepper_canary have this syscall.

After this change, we need sel_ldr from pepper_39 or above to
work.

Fixes #9261

Change-Id: I096973593aa302ade61f259a3a71ebc7c1a57913
Signed-off-by: Shenghou Ma <minux@golang.org>
Reviewed-on: https://go-review.googlesource.com/1755
Reviewed-by: Russ Cox <rsc@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
2015-03-25 02:07:09 +00:00
Michael MacInnis
194ad16b83 os/signal: add ability to ignore signals and restore initial signal handlers
There is currently no way to ignore signals using the os/signal package.
It is possible to catch a signal and do nothing but this is not the same
as ignoring it. The new function Ignore allows a set of signals to be
ignored. The new function Reset allows the initial handlers for a set of
signals to be restored.

Fixes #5572

Change-Id: I5c0f07956971e3a9ff9b9d9631e6e3a08c20df15
Reviewed-on: https://go-review.googlesource.com/3580
Reviewed-by: Ian Lance Taylor <iant@golang.org>
2015-02-16 14:23:09 +00:00
Keith Randall
b2a950bb73 runtime: rename gothrow to throw
Rename "gothrow" to "throw" now that the C version of "throw"
is no longer needed.

This change is purely mechanical except in panic.go where the
old version of "throw" has been deleted.

sed -i "" 's/[[:<:]]gothrow[[:>:]]/throw/g' runtime/*.go

Change-Id: Icf0752299c35958b92870a97111c67bcd9159dc3
Reviewed-on: https://go-review.googlesource.com/2150
Reviewed-by: Minux Ma <minux@golang.org>
Reviewed-by: Dave Cheney <dave@cheney.net>
2014-12-28 06:16:16 +00:00
Keith Randall
1757b5cc74 runtime: fix nacl build
Change-Id: Ifa8b2d1d1cebe72f795db34974584a888d55cbd8
Reviewed-on: https://go-review.googlesource.com/1362
Reviewed-by: Keith Randall <khr@golang.org>
2014-12-11 07:31:32 +00:00
Russ Cox
ad8179281d [dev.cc] runtime: convert nacl support to Go
LGTM=dave
R=minux, dave
CC=golang-codereviews
https://golang.org/cl/181030043
2014-11-21 10:22:18 -05:00