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runtime: doubly-linked sched.midle list

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This will be used by CL 714801 to remove Ms from the middle of the list.

We could simply convert schedlink to the doubly-linked list, bringing
along all other uses of schedlink.

However, CL 714801 removes Ms from the middle of the midle list. It
would be an easy mistake to make to accidentally remove an M from
schedlink, assuming that it is on the midle list when it is actually on
a completely different list. Using separate a list node makes this
impossible.

For #65694.

Change-Id: I6a6a636c223d925fdc30c0c648460cbf5c2af4d6
Reviewed-on: https://go-review.googlesource.com/c/go/+/714800
Reviewed-by: Michael Knyszek <mknyszek@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Auto-Submit: Michael Pratt <mpratt@google.com>
This commit is contained in:
Michael Pratt 2025-10-24 14:54:21 -04:00 • committed by Gopher Robot
parent 046dce0e54
commit 2263d4aabd
2 changed files with 6 additions and 5 deletions
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8
src/runtime/proc.go
View file

@ -849,6 +849,8 @@ func schedinit() {
lockVerifyMSize() lockVerifyMSize()
sched.midle.init(unsafe.Offsetof(m{}.idleNode))
// raceinit must be the first call to race detector. // raceinit must be the first call to race detector.
// In particular, it must be done before mallocinit below calls racemapshadow. // In particular, it must be done before mallocinit below calls racemapshadow.
gp := getg() gp := getg()
@ -6976,8 +6978,7 @@ func schedEnabled(gp *g) bool {
func mput(mp *m) { func mput(mp *m) {
assertLockHeld(&sched.lock) assertLockHeld(&sched.lock)
mp.schedlink = sched.midle sched.midle.push(unsafe.Pointer(mp))
sched.midle.set(mp)
sched.nmidle++ sched.nmidle++
checkdead() checkdead()
} }
@ -6990,9 +6991,8 @@ func mput(mp *m) {
func mget() *m { func mget() *m {
assertLockHeld(&sched.lock) assertLockHeld(&sched.lock)
mp := sched.midle.ptr() mp := (*m)(sched.midle.pop())
if mp != nil { if mp != nil {
sched.midle = mp.schedlink
sched.nmidle-- sched.nmidle--
} }
return mp return mp

3
src/runtime/runtime2.go
View file

@ -665,6 +665,7 @@ type m struct {
park note park note
alllink *m // on allm alllink *m // on allm
schedlink muintptr schedlink muintptr
idleNode listNodeManual
lockedg guintptr lockedg guintptr
createstack [32]uintptr // stack that created this thread, it's used for StackRecord.Stack0, so it must align with it. createstack [32]uintptr // stack that created this thread, it's used for StackRecord.Stack0, so it must align with it.
lockedExt uint32 // tracking for external LockOSThread lockedExt uint32 // tracking for external LockOSThread
@ -875,7 +876,7 @@ type schedt struct {
// When increasing nmidle, nmidlelocked, nmsys, or nmfreed, be // When increasing nmidle, nmidlelocked, nmsys, or nmfreed, be
// sure to call checkdead(). // sure to call checkdead().
midle muintptr // idle m's waiting for work midle listHeadManual // idle m's waiting for work
nmidle int32 // number of idle m's waiting for work nmidle int32 // number of idle m's waiting for work
nmidlelocked int32 // number of locked m's waiting for work nmidlelocked int32 // number of locked m's waiting for work
mnext int64 // number of m's that have been created and next M ID mnext int64 // number of m's that have been created and next M ID