From 3968a5bca4fc0cdb4e2bb9fd6169deafdafc420d Mon Sep 17 00:00:00 2001
From: Russ Cox <rsc@golang.org>
Date: Tue, 4 Mar 2025 10:31:02 -0500
Subject: runtime: handle m0 padding better

The SpinbitMutex experiment requires m structs other than m0
to be allocated in 2048-byte size class, by adding padding.
Do the calculation more explicitly, to avoid future CLs like CL 653335.

Change-Id: I83ae1e86ef3711ab65441f4e487f94b9e1429029
Reviewed-on: https://go-review.googlesource.com/c/go/+/654595
Reviewed-by: Rhys Hiltner <rhys.hiltner@gmail.com>
Reviewed-by: Michael Knyszek <mknyszek@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Auto-Submit: Michael Knyszek <mknyszek@google.com>
---
 src/runtime/proc.go | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

(limited to 'src/runtime/proc.go')

diff --git a/src/runtime/proc.go b/src/runtime/proc.go
index c7ae71a136..8f603021e5 100644
--- a/src/runtime/proc.go
+++ b/src/runtime/proc.go
@@ -2256,7 +2256,7 @@ func allocm(pp *p, fn func(), id int64) *m {
 		unlock(&sched.lock)
 	}
 
-	mp := new(m)
+	mp := &new(mPadded).m
 	mp.mstartfn = fn
 	mcommoninit(mp, id)
 
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