diff --git a/src/cmd/internal/obj/arm/obj5.go b/src/cmd/internal/obj/arm/obj5.go
index 2f04fd73166a03f8be38a7aa38d298aebecf81b5..a975d8a1b3d2be95460885a354c5e6672fcb8771 100644
--- a/src/cmd/internal/obj/arm/obj5.go
+++ b/src/cmd/internal/obj/arm/obj5.go
@@ -703,12 +703,6 @@ func (c *ctxt5) stacksplit(p *obj.Prog, framesize int32) *obj.Prog {
p.To.Type = obj.TYPE_REG
p.To.Reg = REG_R1
- // Mark the stack bound check and morestack call async nonpreemptible.
- // If we get preempted here, when resumed the preemption request is
- // cleared, but we'll still call morestack, which will double the stack
- // unnecessarily. See issue #35470.
- p = c.ctxt.StartUnsafePoint(p, c.newprog)
-
if framesize <= abi.StackSmall {
// small stack: SP < stackguard
// CMP stackguard, SP
@@ -772,8 +766,6 @@ func (c *ctxt5) stacksplit(p *obj.Prog, framesize int32) *obj.Prog {
bls.As = ABLS
bls.To.Type = obj.TYPE_BRANCH
- end := c.ctxt.EndUnsafePoint(bls, c.newprog, -1)
-
var last *obj.Prog
for last = c.cursym.Func().Text; last.Link != nil; last = last.Link {
}
@@ -786,7 +778,6 @@ func (c *ctxt5) stacksplit(p *obj.Prog, framesize int32) *obj.Prog {
spfix.Spadj = -framesize
pcdata := c.ctxt.EmitEntryStackMap(c.cursym, spfix, c.newprog)
- pcdata = c.ctxt.StartUnsafePoint(pcdata, c.newprog)
// MOVW LR, R3
movw := obj.Appendp(pcdata, c.newprog)
@@ -811,16 +802,14 @@ func (c *ctxt5) stacksplit(p *obj.Prog, framesize int32) *obj.Prog {
}
call.To.Sym = c.ctxt.Lookup(morestack)
- pcdata = c.ctxt.EndUnsafePoint(call, c.newprog, -1)
-
// B start
- b := obj.Appendp(pcdata, c.newprog)
+ b := obj.Appendp(call, c.newprog)
b.As = obj.AJMP
b.To.Type = obj.TYPE_BRANCH
b.To.SetTarget(startPred.Link)
b.Spadj = +framesize
- return end
+ return bls
}
var unaryDst = map[obj.As]bool{
diff --git a/src/cmd/internal/obj/arm64/obj7.go b/src/cmd/internal/obj/arm64/obj7.go
index 368a631ff5b5de12cb2d2d8210c1b37c43d36300..1e6ce72c48b324ffe9618ee135036e2af5369bb4 100644
--- a/src/cmd/internal/obj/arm64/obj7.go
+++ b/src/cmd/internal/obj/arm64/obj7.go
@@ -163,12 +163,6 @@ func (c *ctxt7) stacksplit(p *obj.Prog, framesize int32) *obj.Prog {
p.To.Type = obj.TYPE_REG
p.To.Reg = REGRT1
- // Mark the stack bound check and morestack call async nonpreemptible.
- // If we get preempted here, when resumed the preemption request is
- // cleared, but we'll still call morestack, which will double the stack
- // unnecessarily. See issue #35470.
- p = c.ctxt.StartUnsafePoint(p, c.newprog)
-
q := (*obj.Prog)(nil)
if framesize <= abi.StackSmall {
// small stack: SP < stackguard
@@ -235,8 +229,6 @@ func (c *ctxt7) stacksplit(p *obj.Prog, framesize int32) *obj.Prog {
bls.As = ABLS
bls.To.Type = obj.TYPE_BRANCH
- end := c.ctxt.EndUnsafePoint(bls, c.newprog, -1)
-
var last *obj.Prog
for last = c.cursym.Func().Text; last.Link != nil; last = last.Link {
}
@@ -249,7 +241,6 @@ func (c *ctxt7) stacksplit(p *obj.Prog, framesize int32) *obj.Prog {
spfix.Spadj = -framesize
pcdata := c.ctxt.EmitEntryStackMap(c.cursym, spfix, c.newprog)
- pcdata = c.ctxt.StartUnsafePoint(pcdata, c.newprog)
if q != nil {
q.To.SetTarget(pcdata)
@@ -289,9 +280,7 @@ func (c *ctxt7) stacksplit(p *obj.Prog, framesize int32) *obj.Prog {
}
call.To.Sym = c.ctxt.Lookup(morestack)
- // The instructions which unspill regs should be preemptible.
- pcdata = c.ctxt.EndUnsafePoint(call, c.newprog, -1)
- unspill := c.cursym.Func().UnspillRegisterArgs(pcdata, c.newprog)
+ unspill := c.cursym.Func().UnspillRegisterArgs(call, c.newprog)
// B start
jmp := obj.Appendp(unspill, c.newprog)
@@ -300,7 +289,7 @@ func (c *ctxt7) stacksplit(p *obj.Prog, framesize int32) *obj.Prog {
jmp.To.SetTarget(startPred.Link)
jmp.Spadj = +framesize
- return end
+ return bls
}
func progedit(ctxt *obj.Link, p *obj.Prog, newprog obj.ProgAlloc) {
diff --git a/src/cmd/internal/obj/loong64/obj.go b/src/cmd/internal/obj/loong64/obj.go
index f75e2d8716593090c0899ca97c8821302db65318..0d098f74f8929ee58c4912d066b6770bc7f3c4a2 100644
--- a/src/cmd/internal/obj/loong64/obj.go
+++ b/src/cmd/internal/obj/loong64/obj.go
@@ -717,12 +717,6 @@ func (c *ctxt0) stacksplit(p *obj.Prog, framesize int32) *obj.Prog {
p.To.Type = obj.TYPE_REG
p.To.Reg = REG_R20
- // Mark the stack bound check and morestack call async nonpreemptible.
- // If we get preempted here, when resumed the preemption request is
- // cleared, but we'll still call morestack, which will double the stack
- // unnecessarily. See issue #35470.
- p = c.ctxt.StartUnsafePoint(p, c.newprog)
-
var q *obj.Prog
if framesize <= abi.StackSmall {
// small stack: SP < stackguard
@@ -794,7 +788,7 @@ func (c *ctxt0) stacksplit(p *obj.Prog, framesize int32) *obj.Prog {
p.To.Type = obj.TYPE_BRANCH
p.Mark |= BRANCH
- end := c.ctxt.EndUnsafePoint(p, c.newprog, -1)
+ end := p
var last *obj.Prog
for last = c.cursym.Func().Text; last.Link != nil; last = last.Link {
@@ -808,7 +802,6 @@ func (c *ctxt0) stacksplit(p *obj.Prog, framesize int32) *obj.Prog {
spfix.Spadj = -framesize
pcdata := c.ctxt.EmitEntryStackMap(c.cursym, spfix, c.newprog)
- pcdata = c.ctxt.StartUnsafePoint(pcdata, c.newprog)
if q != nil {
q.To.SetTarget(pcdata)
@@ -843,8 +836,6 @@ func (c *ctxt0) stacksplit(p *obj.Prog, framesize int32) *obj.Prog {
}
call.Mark |= BRANCH
- // The instructions which unspill regs should be preemptible.
- pcdata = c.ctxt.EndUnsafePoint(call, c.newprog, -1)
unspill := c.cursym.Func().UnspillRegisterArgs(pcdata, c.newprog)
// JMP start
diff --git a/src/cmd/internal/obj/mips/obj0.go b/src/cmd/internal/obj/mips/obj0.go
index b9152fe57e939fb8eeda74261f4e67b2c450d693..ef242c5f3be66fc6d33e413e5269775c25db7e84 100644
--- a/src/cmd/internal/obj/mips/obj0.go
+++ b/src/cmd/internal/obj/mips/obj0.go
@@ -767,12 +767,6 @@ func (c *ctxt0) stacksplit(p *obj.Prog, framesize int32) *obj.Prog {
p.To.Type = obj.TYPE_REG
p.To.Reg = REG_R1
- // Mark the stack bound check and morestack call async nonpreemptible.
- // If we get preempted here, when resumed the preemption request is
- // cleared, but we'll still call morestack, which will double the stack
- // unnecessarily. See issue #35470.
- p = c.ctxt.StartUnsafePoint(p, c.newprog)
-
var q *obj.Prog
if framesize <= abi.StackSmall {
// small stack: SP < stackguard
@@ -876,8 +870,6 @@ func (c *ctxt0) stacksplit(p *obj.Prog, framesize int32) *obj.Prog {
}
p.Mark |= BRANCH
- p = c.ctxt.EndUnsafePoint(p, c.newprog, -1)
-
// JMP start
p = obj.Appendp(p, c.newprog)
diff --git a/src/cmd/internal/obj/plist.go b/src/cmd/internal/obj/plist.go
index 698e5ace9ccca82bdec797abb7e00fd0ca014a91..5d60e1e3b6295e9eead777f9438c1c31db0d01d6 100644
--- a/src/cmd/internal/obj/plist.go
+++ b/src/cmd/internal/obj/plist.go
@@ -262,16 +262,8 @@ func (ctxt *Link) GloblPos(s *LSym, size int64, flag int, pos src.XPos) {
s.setFIPSType(ctxt)
}
-// EmitEntryLiveness generates PCDATA Progs after p to switch to the
-// liveness map active at the entry of function s. It returns the last
-// Prog generated.
-func (ctxt *Link) EmitEntryLiveness(s *LSym, p *Prog, newprog ProgAlloc) *Prog {
- pcdata := ctxt.EmitEntryStackMap(s, p, newprog)
- pcdata = ctxt.EmitEntryUnsafePoint(s, pcdata, newprog)
- return pcdata
-}
-
-// Similar to EmitEntryLiveness, but just emit stack map.
+// EmitEntryStackMap generates PCDATA Progs after p to switch to the
+// liveness map active at the entry of function s.
func (ctxt *Link) EmitEntryStackMap(s *LSym, p *Prog, newprog ProgAlloc) *Prog {
pcdata := Appendp(p, newprog)
pcdata.Pos = s.Func().Text.Pos
@@ -284,19 +276,6 @@ func (ctxt *Link) EmitEntryStackMap(s *LSym, p *Prog, newprog ProgAlloc) *Prog {
return pcdata
}
-// Similar to EmitEntryLiveness, but just emit unsafe point map.
-func (ctxt *Link) EmitEntryUnsafePoint(s *LSym, p *Prog, newprog ProgAlloc) *Prog {
- pcdata := Appendp(p, newprog)
- pcdata.Pos = s.Func().Text.Pos
- pcdata.As = APCDATA
- pcdata.From.Type = TYPE_CONST
- pcdata.From.Offset = abi.PCDATA_UnsafePoint
- pcdata.To.Type = TYPE_CONST
- pcdata.To.Offset = -1
-
- return pcdata
-}
-
// StartUnsafePoint generates PCDATA Progs after p to mark the
// beginning of an unsafe point. The unsafe point starts immediately
// after p.
diff --git a/src/cmd/internal/obj/ppc64/obj9.go b/src/cmd/internal/obj/ppc64/obj9.go
index 2d2c198ab9f417fa17f82c93f4ba29d100750707..77f13fadf9e4ff5a3a0eb294aeef7fde8e3848d7 100644
--- a/src/cmd/internal/obj/ppc64/obj9.go
+++ b/src/cmd/internal/obj/ppc64/obj9.go
@@ -1364,12 +1364,6 @@ func (c *ctxt9) stacksplit(p *obj.Prog, framesize int32) *obj.Prog {
p.To.Type = obj.TYPE_REG
p.To.Reg = REG_R22
- // Mark the stack bound check and morestack call async nonpreemptible.
- // If we get preempted here, when resumed the preemption request is
- // cleared, but we'll still call morestack, which will double the stack
- // unnecessarily. See issue #35470.
- p = c.ctxt.StartUnsafePoint(p, c.newprog)
-
var q *obj.Prog
if framesize <= abi.StackSmall {
// small stack: SP < stackguard
@@ -1556,8 +1550,6 @@ func (c *ctxt9) stacksplit(p *obj.Prog, framesize int32) *obj.Prog {
p.To.Reg = REG_R2
}
- // The instructions which unspill regs should be preemptible.
- p = c.ctxt.EndUnsafePoint(p, c.newprog, -1)
unspill := c.cursym.Func().UnspillRegisterArgs(p, c.newprog)
// BR start
diff --git a/src/cmd/internal/obj/riscv/obj.go b/src/cmd/internal/obj/riscv/obj.go
index 25d3b11c97d4e84d94cf20015da4f96edd81c4ae..f8ad3bb104e632adc33ce2a219308de6ffdf9359 100644
--- a/src/cmd/internal/obj/riscv/obj.go
+++ b/src/cmd/internal/obj/riscv/obj.go
@@ -978,12 +978,6 @@ func stacksplit(ctxt *obj.Link, p *obj.Prog, cursym *obj.LSym, newprog obj.ProgA
p.To.Type = obj.TYPE_REG
p.To.Reg = REG_X6
- // Mark the stack bound check and morestack call async nonpreemptible.
- // If we get preempted here, when resumed the preemption request is
- // cleared, but we'll still call morestack, which will double the stack
- // unnecessarily. See issue #35470.
- p = ctxt.StartUnsafePoint(p, newprog)
-
var to_done, to_more *obj.Prog
if framesize <= abi.StackSmall {
@@ -1070,8 +1064,6 @@ func stacksplit(ctxt *obj.Link, p *obj.Prog, cursym *obj.LSym, newprog obj.ProgA
}
jalToSym(ctxt, p, REG_X5)
- // The instructions which unspill regs should be preemptible.
- p = ctxt.EndUnsafePoint(p, newprog, -1)
p = cursym.Func().UnspillRegisterArgs(p, newprog)
// JMP start
diff --git a/src/cmd/internal/obj/s390x/objz.go b/src/cmd/internal/obj/s390x/objz.go
index 80b233d832f75920a532a3d8dbaab4cfbdb9d684..a3196c66fdb02396d43590963db5d6654f37f0ba 100644
--- a/src/cmd/internal/obj/s390x/objz.go
+++ b/src/cmd/internal/obj/s390x/objz.go
@@ -327,7 +327,6 @@ func preprocess(ctxt *obj.Link, cursym *obj.LSym, newprog obj.ProgAlloc) {
if !p.From.Sym.NoSplit() {
p, pPreempt, pCheck = c.stacksplitPre(p, autosize) // emit pre part of split check
pPre = p
- p = c.ctxt.EndUnsafePoint(p, c.newprog, -1)
wasSplit = true //need post part of split
}
@@ -657,12 +656,6 @@ func (c *ctxtz) stacksplitPre(p *obj.Prog, framesize int32) (pPre, pPreempt, pCh
p.To.Type = obj.TYPE_REG
p.To.Reg = REG_R3
- // Mark the stack bound check and morestack call async nonpreemptible.
- // If we get preempted here, when resumed the preemption request is
- // cleared, but we'll still call morestack, which will double the stack
- // unnecessarily. See issue #35470.
- p = c.ctxt.StartUnsafePoint(p, c.newprog)
-
if framesize <= abi.StackSmall {
// small stack: SP < stackguard
// CMPUBGE stackguard, SP, label-of-call-to-morestack
@@ -743,7 +736,6 @@ func (c *ctxtz) stacksplitPost(p *obj.Prog, pPre, pPreempt, pCheck *obj.Prog, fr
spfix.Spadj = -framesize
pcdata := c.ctxt.EmitEntryStackMap(c.cursym, spfix, c.newprog)
- pcdata = c.ctxt.StartUnsafePoint(pcdata, c.newprog)
// MOVD LR, R5
p = obj.Appendp(pcdata, c.newprog)
@@ -770,8 +762,6 @@ func (c *ctxtz) stacksplitPost(p *obj.Prog, pPre, pPreempt, pCheck *obj.Prog, fr
p.To.Sym = c.ctxt.Lookup("runtime.morestack")
}
- p = c.ctxt.EndUnsafePoint(p, c.newprog, -1)
-
// BR pCheck
p = obj.Appendp(p, c.newprog)
diff --git a/src/cmd/internal/obj/x86/obj6.go b/src/cmd/internal/obj/x86/obj6.go
index 53c091825414190e32d5bdd0a235dd149185f1c9..7ec93cf6504c591ef4bca6490f18888d66e67f4e 100644
--- a/src/cmd/internal/obj/x86/obj6.go
+++ b/src/cmd/internal/obj/x86/obj6.go
@@ -1106,11 +1106,6 @@ func stacksplit(ctxt *obj.Link, cursym *obj.LSym, p *obj.Prog, newprog obj.ProgA
p.To.Offset = 3 * int64(ctxt.Arch.PtrSize) // G.stackguard1
}
- // Mark the stack bound check and morestack call async nonpreemptible.
- // If we get preempted here, when resumed the preemption request is
- // cleared, but we'll still call morestack, which will double the stack
- // unnecessarily. See issue #35470.
- p = ctxt.StartUnsafePoint(p, newprog)
} else if framesize <= abi.StackBig {
// large stack: SP-framesize <= stackguard-StackSmall
// LEAQ -xxx(SP), tmp
@@ -1135,7 +1130,6 @@ func stacksplit(ctxt *obj.Link, cursym *obj.LSym, p *obj.Prog, newprog obj.ProgA
p.To.Offset = 3 * int64(ctxt.Arch.PtrSize) // G.stackguard1
}
- p = ctxt.StartUnsafePoint(p, newprog) // see the comment above
} else {
// Such a large stack we need to protect against underflow.
// The runtime guarantees SP > objabi.StackBig, but
@@ -1158,8 +1152,6 @@ func stacksplit(ctxt *obj.Link, cursym *obj.LSym, p *obj.Prog, newprog obj.ProgA
p.To.Type = obj.TYPE_REG
p.To.Reg = tmp
- p = ctxt.StartUnsafePoint(p, newprog) // see the comment above
-
p = obj.Appendp(p, newprog)
p.As = sub
p.From.Type = obj.TYPE_CONST
@@ -1189,8 +1181,6 @@ func stacksplit(ctxt *obj.Link, cursym *obj.LSym, p *obj.Prog, newprog obj.ProgA
jls.As = AJLS
jls.To.Type = obj.TYPE_BRANCH
- end := ctxt.EndUnsafePoint(jls, newprog, -1)
-
var last *obj.Prog
for last = cursym.Func().Text; last.Link != nil; last = last.Link {
}
@@ -1202,9 +1192,8 @@ func stacksplit(ctxt *obj.Link, cursym *obj.LSym, p *obj.Prog, newprog obj.ProgA
spfix.As = obj.ANOP
spfix.Spadj = -framesize
- pcdata := ctxt.EmitEntryStackMap(cursym, spfix, newprog)
- spill := ctxt.StartUnsafePoint(pcdata, newprog)
- pcdata = cursym.Func().SpillRegisterArgs(spill, newprog)
+ spill := ctxt.EmitEntryStackMap(cursym, spfix, newprog)
+ pcdata := cursym.Func().SpillRegisterArgs(spill, newprog)
call := obj.Appendp(pcdata, newprog)
call.Pos = cursym.Func().Text.Pos
@@ -1229,9 +1218,7 @@ func stacksplit(ctxt *obj.Link, cursym *obj.LSym, p *obj.Prog, newprog obj.ProgA
progedit(ctxt, callend.Link, newprog)
}
- // The instructions which unspill regs should be preemptible.
- pcdata = ctxt.EndUnsafePoint(callend, newprog, -1)
- unspill := cursym.Func().UnspillRegisterArgs(pcdata, newprog)
+ unspill := cursym.Func().UnspillRegisterArgs(callend, newprog)
jmp := obj.Appendp(unspill, newprog)
jmp.As = obj.AJMP
@@ -1244,7 +1231,7 @@ func stacksplit(ctxt *obj.Link, cursym *obj.LSym, p *obj.Prog, newprog obj.ProgA
q1.To.SetTarget(spill)
}
- return end, rg
+ return jls, rg
}
func isR15(r int16) bool {
diff --git a/src/runtime/preempt.go b/src/runtime/preempt.go
index c41c3558359c0cb625455392a6004173292f6bab..364929f635f61d06ded8b2501657189059edb67d 100644
--- a/src/runtime/preempt.go
+++ b/src/runtime/preempt.go
@@ -173,6 +173,7 @@ func suspendG(gp *g) suspendGState {
// _Gscan bit and thus own the stack.
gp.preemptStop = false
gp.preempt = false
+ gp.preemptRecent = true
gp.stackguard0 = gp.stack.lo + stackGuard
// The goroutine was already at a safe-point
diff --git a/src/runtime/runtime2.go b/src/runtime/runtime2.go
index 05cf345baf6431cf0b6ba8e13d1b0100875183ad..f42c940b8e60d76f7c47fdb51fd040253f9048c7 100644
--- a/src/runtime/runtime2.go
+++ b/src/runtime/runtime2.go
@@ -466,22 +466,29 @@ type g struct {
runnableTime int64 // the amount of time spent runnable, cleared when running, only used when tracking
lockedm muintptr
fipsIndicator uint8
- sig uint32
- writebuf []byte
- sigcode0 uintptr
- sigcode1 uintptr
- sigpc uintptr
- parentGoid uint64 // goid of goroutine that created this goroutine
- gopc uintptr // pc of go statement that created this goroutine
- ancestors *[]ancestorInfo // ancestor information goroutine(s) that created this goroutine (only used if debug.tracebackancestors)
- startpc uintptr // pc of goroutine function
- racectx uintptr
- waiting *sudog // sudog structures this g is waiting on (that have a valid elem ptr); in lock order
- cgoCtxt []uintptr // cgo traceback context
- labels unsafe.Pointer // profiler labels
- timer *timer // cached timer for time.Sleep
- sleepWhen int64 // when to sleep until
- selectDone atomic.Uint32 // are we participating in a select and did someone win the race?
+
+ // preemptRecent is set when a goroutine is preempted. It is
+ // reset by code passing through the synchronous preemption
+ // path. It is used to avoid growing the stack when we were
+ // just preempting, see issue 35470.
+ preemptRecent bool
+
+ sig uint32
+ writebuf []byte
+ sigcode0 uintptr
+ sigcode1 uintptr
+ sigpc uintptr
+ parentGoid uint64 // goid of goroutine that created this goroutine
+ gopc uintptr // pc of go statement that created this goroutine
+ ancestors *[]ancestorInfo // ancestor information goroutine(s) that created this goroutine (only used if debug.tracebackancestors)
+ startpc uintptr // pc of goroutine function
+ racectx uintptr
+ waiting *sudog // sudog structures this g is waiting on (that have a valid elem ptr); in lock order
+ cgoCtxt []uintptr // cgo traceback context
+ labels unsafe.Pointer // profiler labels
+ timer *timer // cached timer for time.Sleep
+ sleepWhen int64 // when to sleep until
+ selectDone atomic.Uint32 // are we participating in a select and did someone win the race?
// goroutineProfiled indicates the status of this goroutine's stack for the
// current in-progress goroutine profile
diff --git a/src/runtime/stack.go b/src/runtime/stack.go
index 2fedaa94216813d9b2d76932c197e04aacf62c7e..67a394cd123f27ca0b14d67427d389e74bd8efc7 100644
--- a/src/runtime/stack.go
+++ b/src/runtime/stack.go
@@ -1075,6 +1075,29 @@ func newstack() {
gopreempt_m(gp) // never return
}
+ if stackguard0 == gp.stack.lo+stackGuard && gp.preemptRecent {
+ // The case happens because of an interaction between synchronous
+ // and asynchronous preemption. First, we set the cooperative
+ // preemption signal (g.stackguard0 = stackPreempt), and as a
+ // result the function fails the stack check and enters its
+ // morestack path. If it gets suspended at that point, we might
+ // give up waiting for it and send an async preempt. That async
+ // preempt gets processed and clears the cooperative preemption
+ // signal (g.stackguard0 = g.stack.lo+stackGuard) and resumes
+ // the function. But even though the cooperative preemption
+ // signal is cleared, we're already on the morestack path and
+ // can't avoid calling morestack. See issue 35470.
+ //
+ // To avoid this problem, if we've been preempted recently,
+ // clear the "preempted recently" flag and resume the G.
+ // If we really did need more stack, the morestack check will
+ // immediately fail and we'll get back here to try again (with
+ // preemptRecent==false, so we don't take this case the
+ // second time).
+ gp.preemptRecent = false
+ gogo(&gp.sched) // never return
+ }
+
// Allocate a bigger segment and move the stack.
oldsize := gp.stack.hi - gp.stack.lo
newsize := oldsize * 2