sync: unaligned atomic write => SIGBUS (darwin/amd64)

[gopherbot]

#!watchflakes
default <- pkg == "golang.org/x/tools/go/buildutil" && test == ""

Issue created automatically to collect these failures.

func (o *Once) doSlow(f func()) {
	o.m.Lock()
	defer o.m.Unlock()
	if o.done.Load() == 0 {
		defer o.done.Store(1)   //       SIGBUS
		f()
	}
}

Example (log):

unexpected fault address 0x428b487f
fatal error: fault
[signal SIGBUS: bus error code=0x2 addr=0x428b487f pc=0xf5ee324]

goroutine 1 gp=0xc000004380 m=0 mp=0xf960400 [running, locked to thread]:
runtime.throw({0xf742163?, 0xf5f4ed1?})
	/Users/swarming/.swarming/w/ir/x/w/goroot/src/runtime/panic.go:1099 +0x48 fp=0xc00006cbe0 sp=0xc00006cbb0 pc=0xf5dbc68
runtime.sigpanic()
	/Users/swarming/.swarming/w/ir/x/w/goroot/src/runtime/signal_unix.go:922 +0x18a fp=0xc00006cc40 sp=0xc00006cbe0 pc=0xf5dd5ea
sync.(*Once).doSlow.deferwrap2()
...
goroutine 5 gp=0xc000005500 m=nil [finalizer wait]:
runtime.gopark(0xf980760?, 0x490013?, 0x78?, 0x26?, 0xf57e41e?)
	/Users/swarming/.swarming/w/ir/x/w/goroot/src/runtime/proc.go:435 +0xce fp=0xc000042630 sp=0xc000042610 pc=0xf5dbd8e
runtime.runfinq()
	/Users/swarming/.swarming/w/ir/x/w/goroot/src/runtime/mfinal.go:196 +0x107 fp=0xc0000427e0 sp=0xc000042630 pc=0xf584ec7
runtime.goexit({})
	/Users/swarming/.swarming/w/ir/x/w/goroot/src/runtime/asm_amd64.s:1700 +0x1 fp=0xc0000427e8 sp=0xc0000427e0 pc=0xf5e2f41
created by runtime.createfing in goroutine 1
	/Users/swarming/.swarming/w/ir/x/w/goroot/src/runtime/mfinal.go:166 +0x3d
FAIL	golang.org/x/tools/go/buildutil	0.031s

— watchflakes

[gopherbot]

Found new dashboard test flakes for:

#!watchflakes
default <- pkg == "golang.org/x/tools/go/buildutil" && test == ""

2024-12-23 20:01 x_tools-go1.24-darwin-amd64_13 tools@93cc684c release-branch.go1.24@16afa6a7 x/tools/go/buildutil (log)

unexpected fault address 0x428b487f
fatal error: fault
[signal SIGBUS: bus error code=0x2 addr=0x428b487f pc=0xf5ee324]

goroutine 1 gp=0xc000004380 m=0 mp=0xf960400 [running, locked to thread]:
runtime.throw({0xf742163?, 0xf5f4ed1?})
	/Users/swarming/.swarming/w/ir/x/w/goroot/src/runtime/panic.go:1099 +0x48 fp=0xc00006cbe0 sp=0xc00006cbb0 pc=0xf5dbc68
runtime.sigpanic()
	/Users/swarming/.swarming/w/ir/x/w/goroot/src/runtime/signal_unix.go:922 +0x18a fp=0xc00006cc40 sp=0xc00006cbe0 pc=0xf5dd5ea
sync.(*Once).doSlow.deferwrap2()
...
goroutine 5 gp=0xc000005500 m=nil [finalizer wait]:
runtime.gopark(0xf980760?, 0x490013?, 0x78?, 0x26?, 0xf57e41e?)
	/Users/swarming/.swarming/w/ir/x/w/goroot/src/runtime/proc.go:435 +0xce fp=0xc000042630 sp=0xc000042610 pc=0xf5dbd8e
runtime.runfinq()
	/Users/swarming/.swarming/w/ir/x/w/goroot/src/runtime/mfinal.go:196 +0x107 fp=0xc0000427e0 sp=0xc000042630 pc=0xf584ec7
runtime.goexit({})
	/Users/swarming/.swarming/w/ir/x/w/goroot/src/runtime/asm_amd64.s:1700 +0x1 fp=0xc0000427e8 sp=0xc0000427e0 pc=0xf5e2f41
created by runtime.createfing in goroutine 1
	/Users/swarming/.swarming/w/ir/x/w/goroot/src/runtime/mfinal.go:166 +0x3d
FAIL	golang.org/x/tools/go/buildutil	0.031s

— watchflakes