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runtime: separate stack freeing from stack shrinking

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Currently, shrinkstack will free the stack if the goroutine is dead.
There are only two places that call shrinkstack: scanstack, which will
never call it if the goroutine is dead; and markrootFreeGStacks, which
only calls it on dead goroutines.

Clean this up by separating stack freeing out of shrinkstack.

Change-Id: I7d7891e620550c32a2220833923a025704986681
Reviewed-on: https://go-review.googlesource.com/c/go/+/170890
Run-TryBot: Austin Clements <austin@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Michael Knyszek <mknyszek@google.com>
This commit is contained in:
Austin Clements 2019-04-03 14:47:55 -04:00
parent ea9859f858
commit 68d89bb8e0
2 changed files with 3 additions and 11 deletions
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4
src/runtime/mgcmark.go
View File

@ -270,7 +270,9 @@ func markrootFreeGStacks() {
// Free stacks.
q := gQueue{list.head, list.head}
for gp := list.head.ptr(); gp != nil; gp = gp.schedlink.ptr() {
shrinkstack(gp)
stackfree(gp.stack)
gp.stack.lo = 0
gp.stack.hi = 0
// Manipulate the queue directly since the Gs are
// already all linked the right way.
q.tail.set(gp)

10
src/runtime/stack.go
View File

@ -1077,16 +1077,6 @@ func gostartcallfn(gobuf *gobuf, fv *funcval) {
// gp must be stopped, but the world need not be.
func shrinkstack(gp *g) {
gstatus := readgstatus(gp)
if gstatus&^_Gscan == _Gdead {
if gp.stack.lo != 0 {
// Free whole stack - it will get reallocated
// if G is used again.
stackfree(gp.stack)
gp.stack.lo = 0
gp.stack.hi = 0
}
return
}
if gp.stack.lo == 0 {
throw("missing stack in shrinkstack")
}