From 2263d4aabdde8a4a466009ecc356501f87c7efb7 Mon Sep 17 00:00:00 2001 From: Michael Pratt Date: Fri, 24 Oct 2025 14:54:21 -0400 Subject: [PATCH] runtime: doubly-linked sched.midle list 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 LUCI-TryBot-Result: Go LUCI Auto-Submit: Michael Pratt --- src/runtime/proc.go | 8 ++++---- src/runtime/runtime2.go | 3 ++- 2 files changed, 6 insertions(+), 5 deletions(-) diff --git a/src/runtime/proc.go b/src/runtime/proc.go index 91740d1fa6..30d2a68626 100644 --- a/src/runtime/proc.go +++ b/src/runtime/proc.go @@ -849,6 +849,8 @@ func schedinit() { lockVerifyMSize() + sched.midle.init(unsafe.Offsetof(m{}.idleNode)) + // raceinit must be the first call to race detector. // In particular, it must be done before mallocinit below calls racemapshadow. gp := getg() @@ -6976,8 +6978,7 @@ func schedEnabled(gp *g) bool { func mput(mp *m) { assertLockHeld(&sched.lock) - mp.schedlink = sched.midle - sched.midle.set(mp) + sched.midle.push(unsafe.Pointer(mp)) sched.nmidle++ checkdead() } @@ -6990,9 +6991,8 @@ func mput(mp *m) { func mget() *m { assertLockHeld(&sched.lock) - mp := sched.midle.ptr() + mp := (*m)(sched.midle.pop()) if mp != nil { - sched.midle = mp.schedlink sched.nmidle-- } return mp diff --git a/src/runtime/runtime2.go b/src/runtime/runtime2.go index 6d1f9b13a2..2b79717703 100644 --- a/src/runtime/runtime2.go +++ b/src/runtime/runtime2.go @@ -665,6 +665,7 @@ type m struct { park note alllink *m // on allm schedlink muintptr + idleNode listNodeManual lockedg guintptr 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 @@ -875,7 +876,7 @@ type schedt struct { // When increasing nmidle, nmidlelocked, nmsys, or nmfreed, be // 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 nmidlelocked int32 // number of locked m's waiting for work mnext int64 // number of m's that have been created and next M ID -- 2.52.0