Revert "runtime: get a better g0 stack bound in needm"

This reverts CL 479915.

Reason for revert: breaks a lot google internal tests.

Change-Id: I13a9422e810af7ba58cbf4a7e6e55f4d8cc0ca51
Reviewed-on: https://go-review.googlesource.com/c/go/+/481055
Reviewed-by: Chressie Himpel <chressie@google.com>
Run-TryBot: Cherry Mui <cherryyz@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>

7 files changed, 7 insertions, 90 deletions

diff --git a/src/runtime/cgo.go b/src/runtime/cgo.go
index 395303552c..6a3eeb5822 100644
--- a/src/runtime/cgo.go
+++ b/src/runtime/cgo.go
@@ -19,7 +19,6 @@ import "unsafe"
 //go:linkname _cgo_yield _cgo_yield
 //go:linkname _cgo_pthread_key_created _cgo_pthread_key_created
 //go:linkname _cgo_bindm _cgo_bindm
-//go:linkname _cgo_getstackbound _cgo_getstackbound
 
 var (
 	_cgo_init                     unsafe.Pointer
@@ -31,7 +30,6 @@ var (
 	_cgo_yield                    unsafe.Pointer
 	_cgo_pthread_key_created      unsafe.Pointer
 	_cgo_bindm                    unsafe.Pointer
-	_cgo_getstackbound            unsafe.Pointer
 )
 
 // iscgo is set to true by the runtime/cgo package
diff --git a/src/runtime/cgo/callbacks.go b/src/runtime/cgo/callbacks.go
index 3c246a88b6..792dd7d086 100644
--- a/src/runtime/cgo/callbacks.go
+++ b/src/runtime/cgo/callbacks.go
@@ -141,12 +141,3 @@ var _cgo_yield unsafe.Pointer
 
 //go:cgo_export_static _cgo_topofstack
 //go:cgo_export_dynamic _cgo_topofstack
-
-// x_cgo_getstackbound gets the thread's C stack size and
-// set the G's stack bound based on the stack size.
-
-//go:cgo_import_static x_cgo_getstackbound
-//go:linkname x_cgo_getstackbound x_cgo_getstackbound
-//go:linkname _cgo_getstackbound _cgo_getstackbound
-var x_cgo_getstackbound byte
-var _cgo_getstackbound = &x_cgo_getstackbound
diff --git a/src/runtime/cgo/gcc_stack_darwin.c b/src/runtime/cgo/gcc_stack_darwin.c
deleted file mode 100644
index 2cc9b76196..0000000000
--- a/src/runtime/cgo/gcc_stack_darwin.c
+++ /dev/null
@@ -1,21 +0,0 @@
-// Copyright 2023 The Go Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style
-// license that can be found in the LICENSE file.
-
-#include <pthread.h>
-#include "libcgo.h"
-
-void
-x_cgo_getstackbound(G *g)
-{
-	void* addr;
-	size_t size;
-	pthread_t p;
-
-	p = pthread_self();
-	addr = pthread_get_stackaddr_np(p); // high address (!)
-	size = pthread_get_stacksize_np(p);
-	g->stacklo = (uintptr)addr - size;
-	// NOTE: don't change g->stackhi. We are called from asmcgocall
-	// which saves the stack depth based on g->stackhi.
-}
diff --git a/src/runtime/cgo/gcc_stack_unix.c b/src/runtime/cgo/gcc_stack_unix.c
deleted file mode 100644
index 3826322661..0000000000
--- a/src/runtime/cgo/gcc_stack_unix.c
+++ /dev/null
@@ -1,32 +0,0 @@
-// Copyright 2023 The Go Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style
-// license that can be found in the LICENSE file.
-
-//go:build unix && !darwin
-
-#ifndef _GNU_SOURCE // pthread_getattr_np
-#define _GNU_SOURCE
-#endif
-
-#include <pthread.h>
-#include "libcgo.h"
-
-void
-x_cgo_getstackbound(G *g)
-{
-	pthread_attr_t attr;
-	void *addr;
-	size_t size;
-
-	pthread_attr_init(&attr);
-#if defined(__GLIBC__) || defined(__sun)
-	pthread_getattr_np(pthread_self(), &attr);  // GNU extension
-	pthread_attr_getstack(&attr, &addr, &size); // low address
-#else
-	pthread_attr_getstacksize(&attr, &size);
-	addr = __builtin_frame_address(0) + 4096 - size;
-#endif
-	g->stacklo = (uintptr)addr;
-	// NOTE: don't change g->stackhi. We are called from asmcgocall
-	// which saves the stack depth based on g->stackhi.
-}
diff --git a/src/runtime/cgo/gcc_stack_windows.c b/src/runtime/cgo/gcc_stack_windows.c
deleted file mode 100644
index 9fcb59cf1a..0000000000
--- a/src/runtime/cgo/gcc_stack_windows.c
+++ /dev/null
@@ -1,7 +0,0 @@
-// Copyright 2023 The Go Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style
-// license that can be found in the LICENSE file.
-
-#include "libcgo.h"
-
-void x_cgo_getstackbound(G *g) {} // no-op for now
diff --git a/src/runtime/proc.go b/src/runtime/proc.go
index 4152aa4852..fd7760a571 100644
--- a/src/runtime/proc.go
+++ b/src/runtime/proc.go
@@ -1889,11 +1889,8 @@ func allocm(pp *p, fn func(), id int64) *m {
 // 1. when the callback is done with the m in non-pthread platforms,
 // 2. or when the C thread exiting on pthread platforms.
 //
-// The signal argument indicates whether we're called from a signal
-// handler.
-//
 //go:nosplit
-func needm(signal bool) {
+func needm() {
 	if (iscgo || GOOS == "windows") && !cgoHasExtraM {
 		// Can happen if C/C++ code calls Go from a global ctor.
 		// Can also happen on Windows if a global ctor uses a
@@ -1942,23 +1939,14 @@ func needm(signal bool) {
 	osSetupTLS(mp)
 
 	// Install g (= m->g0) and set the stack bounds
-	// to match the current stack. If we don't actually know
+	// to match the current stack. We don't actually know
 	// how big the stack is, like we don't know how big any
-	// scheduling stack is, but we assume there's at least 32 kB.
-	// If we can get a more accurate stack bound from pthread,
-	// use that.
+	// scheduling stack is, but we assume there's at least 32 kB,
+	// which is more than enough for us.
 	setg(mp.g0)
 	gp := getg()
 	gp.stack.hi = getcallersp() + 1024
 	gp.stack.lo = getcallersp() - 32*1024
-	if !signal && _cgo_getstackbound != nil {
-		// Don't adjust if called from the signal handler.
-		// We are on the signal stack, not the pthread stack.
-		// (We could get the stack bounds from sigaltstack, but
-		// we're getting out of the signal handler very soon
-		// anyway. Not worth it.)
-		asmcgocall(_cgo_getstackbound, unsafe.Pointer(gp))
-	}
 	gp.stackguard0 = gp.stack.lo + _StackGuard
 
 	// Should mark we are already in Go now.
@@ -1979,7 +1967,7 @@ func needm(signal bool) {
 //
 //go:nosplit
 func needAndBindM() {
-	needm(false)
+	needm()
 
 	if _cgo_pthread_key_created != nil && *(*uintptr)(_cgo_pthread_key_created) != 0 {
 		cgoBindM()
diff --git a/src/runtime/signal_unix.go b/src/runtime/signal_unix.go
index c7edbcd239..d1719b22ff 100644
--- a/src/runtime/signal_unix.go
+++ b/src/runtime/signal_unix.go
@@ -585,7 +585,7 @@ func adjustSignalStack(sig uint32, mp *m, gsigStack *gsignalStack) bool {
 
 	// sp is not within gsignal stack, g0 stack, or sigaltstack. Bad.
 	setg(nil)
-	needm(true)
+	needm()
 	if st.ss_flags&_SS_DISABLE != 0 {
 		noSignalStack(sig)
 	} else {
@@ -1068,7 +1068,7 @@ func badsignal(sig uintptr, c *sigctxt) {
 		exit(2)
 		*(*uintptr)(unsafe.Pointer(uintptr(123))) = 2
 	}
-	needm(true)
+	needm()
 	if !sigsend(uint32(sig)) {
 		// A foreign thread received the signal sig, and the
 		// Go code does not want to handle it.