Frameless function is an interesting case for call injection
espcially for LR architectures. Extend the test for this case.

Change-Id: I074090d09eeaf642e71e3f44fea216f66d39b817
Reviewed-on: https://go-review.googlesource.com/c/go/+/202339
Run-TryBot: Cherry Zhang <cherryyz@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Austin Clements <austin@google.com>

Change-Id: I9cfaba4f1af23ab67627bf496739311e4d1984c3
Reviewed-on: https://go-review.googlesource.com/c/go/+/205245Reviewed-by: Robert Griesemer <gri@golang.org>
Run-TryBot: Robert Griesemer <gri@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

Introduce a mechanism for marking architecture-specific Ops
unsafe. And mark ones that use REGTMP on ARM64, as for async
preemption we will be using REGTMP as a temporary register in the
injected call.

Change-Id: I8ff22e87d8f9cb10d02a2f0af7c12ad6d7d58f54
Reviewed-on: https://go-review.googlesource.com/c/go/+/203459
Run-TryBot: Cherry Zhang <cherryyz@google.com>
Reviewed-by: Austin Clements <austin@google.com>

For async preemption, we will be using REGTMP as a temporary
register in injected call on ARM64, which will clobber it. So any
code that uses REGTMP is not safe for async preemption.

For ZeroRange, which is inserted at the function entry where
there is no register live, we could just use a different register
and avoid REGTMP.

Change-Id: I3db763828df6846908c9843a9912597efb9efcdf
Reviewed-on: https://go-review.googlesource.com/c/go/+/203458
Run-TryBot: Cherry Zhang <cherryyz@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Austin Clements <austin@google.com>

This CL adds support of call injection and async preemption on
ARM.

Injected call, like sigpanic, has special frame layout. Teach
traceback to handle it.

Change-Id: I887e90134fbf8a676b73c26321c50b3c4762dba4
Reviewed-on: https://go-review.googlesource.com/c/go/+/202338
Run-TryBot: Cherry Zhang <cherryyz@google.com>
Reviewed-by: Austin Clements <austin@google.com>

Actual fix will be submitted to x/tools and vendored.
This is just an end-to-end test for vet after that is done.

Update #35264

Change-Id: I1a63f607e7cfa7aafee23c2c081086c276d3c38c
Reviewed-on: https://go-review.googlesource.com/c/go/+/204538
Run-TryBot: Keith Randall <khr@golang.org>
Reviewed-by: Alan Donovan <adonovan@google.com>

The logic for keeping arguments alive for calls to //go:uintptrescapes
functions was only applying to direct function calls. This CL changes
it to also apply to direct method calls, which should address most
uses of Proc.Call and LazyProc.Call.

It's still an open question (#34684) whether other call forms (e.g.,
method expressions, or indirect calls via function values, method
values, or interfaces).

Fixes #34474.

Change-Id: I874f97145972b0e237a4c9e8926156298f4d6ce0
Reviewed-on: https://go-review.googlesource.com/c/go/+/198043
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Keith Randall <khr@golang.org>

Programs should always check the error return of Close for a file opened
for writing. Update the example code in the comment to mention this.

Change-Id: I2ff6866ff1fe23b47c54268ac8e182210cc876c5
Reviewed-on: https://go-review.googlesource.com/c/go/+/202137Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

As a side-effect ensure that netpollinited only reports true when
netpoll initialization is complete.

Fixes #35282
Updates #35353

Change-Id: I21f08a04fcf229e0de5e6b5ad89c990426ae9b89
Reviewed-on: https://go-review.googlesource.com/c/go/+/204937
Run-TryBot: Ian Lance Taylor <iant@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

Fixes #35264

Change-Id: Id540a48f593d8ac1b414551255c5eff24666aa0b
Reviewed-on: https://go-review.googlesource.com/c/go/+/205240
Run-TryBot: Keith Randall <khr@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

This CL extends cmd/compile's experimental libFuzzer support with
calls to __sanitizer_cov_trace_{,const_}cmp{1,2,4,8}. This allows much
more efficient fuzzing of comparisons.

Only supports amd64 and arm64 for now.

Updates #14565.

Change-Id: Ibf82a8d9658f2bc50d955bdb1ae26723a3f0584d
Reviewed-on: https://go-review.googlesource.com/c/go/+/203887
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Keith Randall <khr@golang.org>

This CL adds experimental coverage instrumentation similar to what
github.com/dvyukov/go-fuzz produces in its -libfuzzer mode. The
coverage can be enabled by compiling with -d=libfuzzer. It's intended
to be used in conjunction with -buildmode=c-archive to produce an ELF
archive (.a) file that can be linked with libFuzzer. See #14565 for
example usage.

The coverage generates a unique 8-bit counter for each basic block in
the original source code, and emits an increment operation. These
counters are then collected into the __libfuzzer_extra_counters ELF
section for use by libFuzzer.

Updates #14565.

Change-Id: I239758cc0ceb9ca1220f2d9d3d23b9e761db9bf1
Reviewed-on: https://go-review.googlesource.com/c/go/+/202117
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Keith Randall <khr@golang.org>

This change renames the "round" function to the more appropriately named
"alignUp" which rounds an integer up to the next multiple of a power of
two.

This change also adds the alignDown function, which is almost like
alignUp but rounds down to the previous multiple of a power of two.

With these two functions, we also go and replace manual rounding code
with it where we can.

Change-Id: Ie1487366280484dcb2662972b01b4f7135f72fec
Reviewed-on: https://go-review.googlesource.com/c/go/+/190618Reviewed-by: Austin Clements <austin@google.com>
Reviewed-by: Keith Randall <khr@golang.org>

Fixes #35082
Updates #6853

Change-Id: I4eeb0e15f534cff57fefb6039cd33fadf15b946e
Reviewed-on: https://go-review.googlesource.com/c/go/+/205139Reviewed-by: Emmanuel Odeke <emm.odeke@gmail.com>
Reviewed-by: David Crawshaw <crawshaw@golang.org>

This change makes it so that the GC pacer's trigger ratio can never fall
below 0.6. Upcoming changes to the allocator make it significantly more
scalable and thus much faster in certain cases, creating a large gap
between the performance of allocation and scanning. The consequence of
this is that the trigger ratio can drop very low (0.07 was observed) in
order to drop GC utilization. A low trigger ratio like this results in a
high amount of black allocations, which causes the live heap to appear
larger, and thus the heap, and RSS, grows to a much higher stable point.

This change alleviates the problem by placing a lower bound on the
trigger ratio. The expected (and confirmed) effect of this is that
utilization in certain scenarios will no longer converge to the expected
25%, and may go higher. As a result of this artificially high trigger
ratio, more time will also be spent doing GC assists compared to
dedicated mark workers, since the GC will be on for an artifically short
fraction of time (artificial with respect to the pacer). The biggest
concern of this change is that allocation latency will suffer as a
result, since there will now be more assists. But, upcoming changes to
the allocator reduce the latency enough to outweigh the expected
increase in latency from this change, without the blowup in RSS observed
from the changes to the allocator.

Updates #35112.

Change-Id: Idd7c94fa974d0de673304c4397e716e89bfbf09b
Reviewed-on: https://go-review.googlesource.com/c/go/+/200439Reviewed-by: Austin Clements <austin@google.com>

The js.Value struct now contains a pointer, so a finalizer can
determine if the value is not referenced by Go any more.

Unfortunately this breaks Go's == operator with js.Value. This change
adds a new Equal method to check for the equality of two Values.
This is a breaking change. The == operator is now disallowed to
not silently break code.

Additionally the helper methods IsUndefined, IsNull and IsNaN got added.

Fixes #35111

Change-Id: I58a50ca18f477bf51a259c668a8ba15bfa76c955
Reviewed-on: https://go-review.googlesource.com/c/go/+/203600
Run-TryBot: Richard Musiol <neelance@gmail.com>
Reviewed-by: Cherry Zhang <cherryyz@google.com>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

This is a rough attempt at restoring -m=2 escape analysis diagnostics
on par with those that were available with esc.go. It's meant to be
simple and non-invasive.

For example, given this random example from bytes/reader.go:

138	func (r *Reader) WriteTo(w io.Writer) (n int64, err error) {
...
143	        b := r.s[r.i:]
144	        m, err := w.Write(b)

esc.go used to report:

bytes/reader.go:138:7: leaking param content: r
bytes/reader.go:138:7:       from r.s (dot of pointer) at bytes/reader.go:143:8
bytes/reader.go:138:7:       from b (assigned) at bytes/reader.go:143:4
bytes/reader.go:138:7:       from w.Write(b) (parameter to indirect call) at bytes/reader.go:144:19

With this CL, escape.go now reports:

bytes/reader.go:138:7: parameter r leaks to {heap} with derefs=1:
bytes/reader.go:138:7:   flow: b = *r:
bytes/reader.go:138:7:     from r.s (dot of pointer) at bytes/reader.go:143:8
bytes/reader.go:138:7:     from r.s[r.i:] (slice) at bytes/reader.go:143:10
bytes/reader.go:138:7:     from b := r.s[r.i:] (assign) at bytes/reader.go:143:4
bytes/reader.go:138:7:   flow: {heap} = b:
bytes/reader.go:138:7:     from w.Write(b) (call parameter) at bytes/reader.go:144:19

Updates #31489.

Change-Id: I0c2b943a0f9ce6345bfff61e1c635172a9290cbb
Reviewed-on: https://go-review.googlesource.com/c/go/+/196959
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
Reviewed-by: David Chase <drchase@google.com>

Add a 'single lane' SIMD implemementation of the single byte count
function for use on machines that support the vector facility. This
allows up to 16 bytes to be counted per loop iteration.

We can probably improve performance further by adding more 'lanes'
(i.e. counting more bytes in parallel) however this will increase
the complexity of the function so I'm not sure it is worth doing
yet.

name                old speed      new speed       delta
pkg:strings goos:linux goarch:s390x
CountByte/10         789MB/s ± 0%   1131MB/s ± 0%    +43.44%  (p=0.000 n=9+9)
CountByte/32         936MB/s ± 0%   3236MB/s ± 0%   +245.87%  (p=0.000 n=8+9)
CountByte/4096      1.06GB/s ± 0%  21.26GB/s ± 0%  +1907.07%  (p=0.000 n=10+10)
CountByte/4194304   1.06GB/s ± 0%  20.54GB/s ± 0%  +1838.50%  (p=0.000 n=10+10)
CountByte/67108864  1.06GB/s ± 0%  18.31GB/s ± 0%  +1629.51%  (p=0.000 n=10+10)
pkg:bytes goos:linux goarch:s390x
CountSingle/10       800MB/s ± 0%    986MB/s ± 0%    +23.21%  (p=0.000 n=9+10)
CountSingle/32       925MB/s ± 0%   2744MB/s ± 0%   +196.55%  (p=0.000 n=9+10)
CountSingle/4K      1.26GB/s ± 0%  19.44GB/s ± 0%  +1445.59%  (p=0.000 n=10+10)
CountSingle/4M      1.26GB/s ± 0%  20.28GB/s ± 0%  +1510.26%  (p=0.000 n=8+10)
CountSingle/64M     1.23GB/s ± 0%  17.78GB/s ± 0%  +1350.67%  (p=0.000 n=9+10)

Change-Id: I230d57905db92a8fdfc50b1d5be338941ae3a7a1
Reviewed-on: https://go-review.googlesource.com/c/go/+/199979
Run-TryBot: Michael Munday <mike.munday@ibm.com>
Reviewed-by: Keith Randall <khr@golang.org>

TestArchiveBuildInvokeWithExec is failing on darwin due to
duplicated symbols, because the C definition (int fortytwo;) is
copied to two generated cgo sources. In fact, this test is about
building c-archive, but doesn't need to import "C". Removed the
"C" import.

Change-Id: I3a17546e01272a7ae37e6417791ab949fb44597e
Reviewed-on: https://go-review.googlesource.com/c/go/+/205278
Run-TryBot: Cherry Zhang <cherryyz@google.com>
Reviewed-by: Than McIntosh <thanm@google.com>

When dropping a P, if it has any timers, and if some thread is
sleeping in the netpoller, wake the netpoller to run the P's timers.
This mitigates races between the netpoller deciding how long to sleep
and a new timer being added.

In sysmon, if all P's are idle, check the timers to decide how long to sleep.
This avoids oversleeping if no thread is using the netpoller.
This can happen in particular if some threads use runtime.LockOSThread,
as those threads do not block in the netpoller.

Also, print the number of timers per P for GODEBUG=scheddetail=1.

Before this CL, TestLockedDeadlock2 would fail about 1% of the time.
With this CL, I ran it 150,000 times with no failures.

Updates #6239
Updates #27707
Fixes #35274
Fixes #35288

Change-Id: I7e5193e6c885e567f0b1ee023664aa3e2902fcd1
Reviewed-on: https://go-review.googlesource.com/c/go/+/204800
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Michael Knyszek <mknyszek@google.com>

This CL makes these changes to the hash/maphash API to make it fit a bit
more into the standard library:

 - Move some of the package doc onto type Hash, so that `go doc maphash.Hash` shows it.

 - Instead of having identical AddBytes and Write methods,
   standardize on Write, the usual name for this function.
   Similarly, AddString -> WriteString, AddByte -> WriteByte.

 - Instead of having identical Hash and Sum64 methods,
   standardize on Sum64 (for hash.Hash64). Dropping the "Hash" method
   also helps because Hash is usually reserved to mean the state of a
   hash function (hash.Hash etc), not the hash value itself.

 - Make an uninitialized hash.Hash auto-seed with a random seed.
   It is critical that users not use the same seed for all hash functions
   in their program, at least not accidentally. So the Hash implementation
   must either panic if uninitialized or initialize itself.
   Initializing itself is less work for users and can be done lazily.

 - Now that the zero hash.Hash is useful, drop maphash.New in favor of
   new(maphash.Hash) or simply declaring a maphash.Hash.

 - Add a [0]func()-typed field to the Hash so that Hashes cannot be compared.
   (I considered doing the same for Seed but comparing seeds seems OK.)

 - Drop the integer argument from MakeSeed, to match the original design
   in golang.org/issue/28322. There is no point to giving users control
   over the specific seed bits, since we want the interpretation of those
   bits to be different in every different process. The only thing users
   need is to be able to create a new random seed at each call.
   (Fixes a TODO in MakeSeed's public doc comment.)

This API is new in Go 1.14, so these changes do not violate the compatibility promise.

Fixes #35060.
Fixes #35348.

Change-Id: Ie6fecc441f3f5ef66388c6ead92e875c0871f805
Reviewed-on: https://go-review.googlesource.com/c/go/+/205069
Run-TryBot: Russ Cox <rsc@golang.org>
Reviewed-by: Alan Donovan <adonovan@google.com>
Reviewed-by: Keith Randall <khr@golang.org>

Change-Id: Ie68fd4fe2879e6b5417a1a4240971e3d837bf115
Reviewed-on: https://go-review.googlesource.com/c/go/+/204377
Run-TryBot: Filippo Valsorda <filippo@golang.org>
Run-TryBot: Katie Hockman <katie@golang.org>
Reviewed-by: Katie Hockman <katie@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

We absorbed Not into most integer comparisons but not into pointer
and floating point equality checks.

The new cases trigger more than 300 times during make.bash.

Change-Id: I77c6b31fcacde10da5470b73fc001a19521ce78d
Reviewed-on: https://go-review.googlesource.com/c/go/+/200618
Run-TryBot: Michael Munday <mike.munday@ibm.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Keith Randall <khr@golang.org>

CL 200958 adds skipping empty init function feature without any tests
for it. A codegen test sounds ideal, but it's unlikely that we can make
one for now, so use a program to manipulate runtime/proc.go:initTask
directly.

Updates #34869

Change-Id: I2683b9a1ace36af6861af02a3a9fb18b3110b282
Reviewed-on: https://go-review.googlesource.com/c/go/+/204217
Run-TryBot: Cuong Manh Le <cuong.manhle.vn@gmail.com>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>
Reviewed-by: Keith Randall <khr@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

Speed up nanotime1 and walltime1 on MIPS64 with vDSO, just like the
other vDSO-enabled targets.

Benchmark numbers on Loongson 3A3000 (GOARCH=mips64le, 1.4GHz) against
current master:

benchmark                old ns/op     new ns/op     delta
BenchmarkNow             868           293           -66.24%
BenchmarkNowUnixNano     851           296           -65.22%

Performance hit on fallback case, tested by using a wrong vDSO symbol name:

benchmark                old ns/op     new ns/op     delta
BenchmarkNow             868           889           +2.42%
BenchmarkNowUnixNano     851           893           +4.94%

Change-Id: Ibfb48893cd060536359863ffee7624c00def646b
GitHub-Last-Rev: 03a58ac2e4e036a4f61227cfd013082871e92863
GitHub-Pull-Request: golang/go#35181
Reviewed-on: https://go-review.googlesource.com/c/go/+/203578
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Cherry Zhang <cherryyz@google.com>

When linking a Go archive, if the archiver invocation is the very last
thing that needs to happen in the link (no "atexit" cleanups required
remove the locally created tmpdir) then call syscall.Exec to invoke
the archiver command instead of the usual exec.Command. This has the
effect of reducing peak memory use for the linker overall, since we
don't be holding onto all of the linker's live memory while the
archiver is running.

Change-Id: Ibbe22d8d67a70cc2a4f91c68aab56d19fb77c393
Reviewed-on: https://go-review.googlesource.com/c/go/+/203821
Run-TryBot: Than McIntosh <thanm@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Reviewed-by: Cherry Zhang <cherryyz@google.com>

For restoring condition code (we already support IPM instruction
for saving condition code).

Change-Id: I56d376df44a5f831134a130d052521cec6b5b781
Reviewed-on: https://go-review.googlesource.com/c/go/+/204104Reviewed-by: Michael Munday <mike.munday@ibm.com>

When we do a successful recover of a panic, we resume normal execution by
returning from the frame that had the deferred call that did the recover (after
executing any remaining deferred calls in that frame).

However, suppose we have called runtime.Goexit and there is a panic during one of the
deferred calls run by the Goexit. Further assume that there is a deferred call in
the frame of the Goexit or a parent frame that does a recover. Then the recovery
process will actually resume normal execution above the Goexit frame and hence
abort the Goexit.  We will not terminate the thread as expected, but continue
running in the frame above the Goexit.

To fix this, we explicitly create a _panic object for a Goexit call. We then
change the "abort" behavior for Goexits, but not panics. After a recovery, if the
top-level panic is actually a Goexit that is marked to be aborted, then we return
to the Goexit defer-processing loop, so that the Goexit is not actually aborted.

Actual code changes are just panic.go, runtime2.go, and funcid.go. Adjusted the
test related to the new Goexit behavior (TestRecoverBeforePanicAfterGoexit) and
added several new tests of aborted panics (whose behavior has not changed).

Fixes #29226

Change-Id: Ib13cb0074f5acc2567a28db7ca6912cfc47eecb5
Reviewed-on: https://go-review.googlesource.com/c/go/+/200081
Run-TryBot: Dan Scales <danscales@google.com>
Reviewed-by: Keith Randall <khr@golang.org>

From CL 199979, I noticed that there were some
instructions not covered by the test cases. Added those in this CL.

Additional tests for assembly instructions are also added
based on suggestions made during the review of this CL.

Previously, VSB and VSH are not included in asmz.go, they were also
added in this patch.

Change-Id: I6060a9813b483a161d61ad2240c30eec6de61536
Reviewed-on: https://go-review.googlesource.com/c/go/+/203721Reviewed-by: Michael Munday <mike.munday@ibm.com>

We used to pass -no_pie to external linker on darwin/arm, which
is incompatible with -fembed-bitcode. CL 201358 attempted to
remove the -no_pie flag, but it resulted the darwin linker to
complain about absolute addressing in TEXT segment.

On darwin/arm, we already get away from absolute addressing in
the TEXT section. The complained absolute addressing is in
RODATA, which was embedded in the TEXT segment. This CL moves
RODATA to the DATA segment, like what we already did on ARM64
and on AMD64 in c-archive/c-shared buildmodes for the same reason.
So there is no absolute addressing in the TEXT segment, which
allows us to remove -no_pie flag.

Fixes #35252.
Updates #32963.

Change-Id: Id6e3a594cb066d257d4f58fadb4a3ee4672529f7
Reviewed-on: https://go-review.googlesource.com/c/go/+/205060Reviewed-by: Elias Naur <mail@eliasnaur.com>

Fixes #32111

Change-Id: I7078947889d1e126d9679fb28f27b3fa6ce133ef
Reviewed-on: https://go-review.googlesource.com/c/go/+/201359Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

Fixes #35327

Change-Id: I3726bfad24851a0bef8891014f7c5a7c48352307
Reviewed-on: https://go-review.googlesource.com/c/go/+/205077
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

POWER9 (ISA 3.0) introduced a new format of load/store instructions to
implement indexed load/store quadword, using an immediate value instead
of a register index.

This change adds support for this new instruction encoding and adds the
new load/store quadword instructions (lxv/stxv) to the assembler.

This change also adds the missing XX1-form loads/stores (halfword and byte)
included in ISA 3.0.

Change-Id: Ibcdf53c342d7a352d64a9403c2fe7b25be9c3b24
Reviewed-on: https://go-review.googlesource.com/c/go/+/200399
Run-TryBot: Carlos Eduardo Seo <cseo@linux.vnet.ibm.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Lynn Boger <laboger@linux.vnet.ibm.com>

Replace

buf := [HUGE_CONST]*T)(unsafe.Pointer(p))[:]

with

buf := [HUGE_CONST]*T)(unsafe.Pointer(p))[:n:n]

Pointer p points to n of T elements. New unsafe pointer conversion
logic verifies that both first and last elements point into the
same Go variable. And this change adjusts all code to comply with
this rule.

Verified by running

go test -a -short -gcflags=all=-d=checkptr crypto/x509

The test does not fail even with original version of this code. I
suspect it is because all variables I changed live outside of Go
memory. But I am just guessing, I don't really know how pointer
checker works.

Updates golang/go#34972

Change-Id: Ibc33fdc9e2023d9b14905c9badf2f0b683999ab8
Reviewed-on: https://go-review.googlesource.com/c/go/+/204621
Run-TryBot: Alex Brainman <alex.brainman@gmail.com>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

We don't async preempt assembly functions. We do that by checking
whether the function has a local pointer map, and assume it is
an assembly (or, non-Go) function if there isn't one. However,
assembly functions marked with NO_LOCAL_POINTERS still have local
pointer maps, and we wouldn't identify them. For them, check for
the special pointer map runtime.no_pointers_stackmap as well, and
treat them as not async preemptible.

Change-Id: I1301e3b4d35893c31c4c5a5147a0d775987bd6f4
Reviewed-on: https://go-review.googlesource.com/c/go/+/202337Reviewed-by: Austin Clements <austin@google.com>

This adds a test of preempting a loop containing no synchronous safe
points for STW and stack scanning.

We couldn't add this test earlier because it requires scheduler, STW,
and stack scanning preemption to all be working.

For #10958, #24543.

Change-Id: I73292db78ca3d14aab11bdafd26d03986920ef0a
Reviewed-on: https://go-review.googlesource.com/c/go/+/201777
Run-TryBot: Austin Clements <austin@google.com>
Reviewed-by: Cherry Zhang <cherryyz@google.com>

This adds signal-based preemption to preemptone.

Since STW and forEachP ultimately use preemptone, this also makes
these work with async preemption.

This also makes freezetheworld more robust so tracebacks from fatal
panics should be far less likely to report "goroutine running on other
thread; stack unavailable".

For #10958, #24543. (This doesn't fix it yet because asynchronous
preemption only works on POSIX platforms on 386 and amd64 right now.)

Change-Id: If776181dd5a9b3026a7b89a1b5266521b95a5f61
Reviewed-on: https://go-review.googlesource.com/c/go/+/201762
Run-TryBot: Austin Clements <austin@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Cherry Zhang <cherryyz@google.com>

This adds support for pausing a running G by sending a signal to its
M.

The main complication is that we want to target a G, but can only send
a signal to an M. Hence, the protocol we use is to simply mark the G
for preemption (which we already do) and send the M a "wake up and
look around" signal. The signal checks if it's running a G with a
preemption request and stops it if so in the same way that stack check
preemptions stop Gs. Since the preemption may fail (the G could be
moved or the signal could arrive at an unsafe point), we keep a count
of the number of received preemption signals. This lets stopG detect
if its request failed and should be retried without an explicit
channel back to suspendG.

For #10958, #24543.

Change-Id: I3e1538d5ea5200aeb434374abb5d5fdc56107e53
Reviewed-on: https://go-review.googlesource.com/c/go/+/201760
Run-TryBot: Austin Clements <austin@google.com>
Reviewed-by: Cherry Zhang <cherryyz@google.com>

This adds support for scanning the stack when a goroutine is stopped
at an async safe point. This is not yet lit up because asyncPreempt is
not yet injected, but prepares us for that.

This works by conservatively scanning the registers dumped in the
frame of asyncPreempt and its parent frame, which was stopped at an
asynchronous safe point.

Conservative scanning works by only marking words that are pointers to
valid, allocated heap objects. One complication is pointers to stack
objects. In this case, we can't determine if the stack object is still
"allocated" or if it was freed by an earlier GC. Hence, we need to
propagate the conservative-ness of scanning stack objects: if all
pointers found to a stack object were found via conservative scanning,
then the stack object itself needs to be scanned conservatively, since
its pointers may point to dead objects.

For #10958, #24543.

Change-Id: I7ff84b058c37cde3de8a982da07002eaba126fd6
Reviewed-on: https://go-review.googlesource.com/c/go/+/201761
Run-TryBot: Austin Clements <austin@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Cherry Zhang <cherryyz@google.com>

This adds asynchronous preemption function for amd64 and 386. These
functions spill and restore all register state that can be used by
user Go code.

For the moment we stub out the other arches.

For #10958, #24543.

Change-Id: I6f93fabe9875f4834922a5712362e79045c00aca
Reviewed-on: https://go-review.googlesource.com/c/go/+/201759
Run-TryBot: Austin Clements <austin@google.com>
Reviewed-by: Cherry Zhang <cherryyz@google.com>