runtime:cpu2: TestCoroCgoCallback failures

[gopherbot]

#!watchflakes
default <- pkg == "runtime:cpu2" && test == "TestCoroCgoCallback"

Issue created automatically to collect these failures.

Example (log):

=== RUN   TestCoroCgoCallback
--- FAIL: TestCoroCgoCallback (0.00s)
panic: /home/swarming/.swarming/w/ir/x/w/goroot/bin/go env CGO_ENABLED: [] [recovered, repanicked]

goroutine 2560 gp=0xc000103180 m=4 mp=0xc000104008 [running]:
panic({0x4aa260?, 0xc0020447d0?})
	/home/swarming/.swarming/w/ir/x/w/goroot/src/runtime/panic.go:802 +0x18c fp=0xc0000b3798 sp=0xc0000b36d8 pc=0xa123c
testing.tRunner.func1.2({0x4aa260, 0xc0020447d0})
	/home/swarming/.swarming/w/ir/x/w/goroot/src/testing/testing.go:1869 +0x1ec fp=0xc0000b3858 sp=0xc0000b3798 pc=0x14989c
testing.tRunner.func1()
...
runtime_test.TestChanSendBarrier(0xc0003f8540?)
	/home/swarming/.swarming/w/ir/x/w/goroot/src/runtime/chanbarrier_test.go:53 +0x2c fp=0xc0002c5f30 sp=0xc0002c5f08 pc=0x36b55c
testing.tRunner(0xc0003f8540, 0x587b90)
	/home/swarming/.swarming/w/ir/x/w/goroot/src/testing/testing.go:1931 +0x108 fp=0xc0002c5f90 sp=0xc0002c5f30 pc=0x148ee8
testing.(*T).Run.gowrap1()
	/home/swarming/.swarming/w/ir/x/w/goroot/src/testing/testing.go:1994 +0x50 fp=0xc0002c5fc0 sp=0xc0002c5f90 pc=0x149f30
runtime.goexit({})
	/home/swarming/.swarming/w/ir/x/w/goroot/src/runtime/asm_ppc64x.s:1015 +0x4 fp=0xc0002c5fc0 sp=0xc0002c5fc0 pc=0xa9924
created by testing.(*T).Run in goroutine 1
	/home/swarming/.swarming/w/ir/x/w/goroot/src/testing/testing.go:1994 +0x43c

— watchflakes

[gopherbot]

Found new dashboard test flakes for:

#!watchflakes
default <- pkg == "runtime:cpu2" && test == "TestCoroCgoCallback"

2025-06-09 17:58 go1.25-openbsd-ppc64 release-branch.go1.25@848a768b runtime:cpu2.TestCoroCgoCallback (log)

=== RUN   TestCoroCgoCallback
--- FAIL: TestCoroCgoCallback (0.00s)
panic: /home/swarming/.swarming/w/ir/x/w/goroot/bin/go env CGO_ENABLED: [] [recovered, repanicked]

goroutine 2560 gp=0xc000103180 m=4 mp=0xc000104008 [running]:
panic({0x4aa260?, 0xc0020447d0?})
	/home/swarming/.swarming/w/ir/x/w/goroot/src/runtime/panic.go:802 +0x18c fp=0xc0000b3798 sp=0xc0000b36d8 pc=0xa123c
testing.tRunner.func1.2({0x4aa260, 0xc0020447d0})
	/home/swarming/.swarming/w/ir/x/w/goroot/src/testing/testing.go:1869 +0x1ec fp=0xc0000b3858 sp=0xc0000b3798 pc=0x14989c
testing.tRunner.func1()
...
runtime_test.TestChanSendBarrier(0xc0003f8540?)
	/home/swarming/.swarming/w/ir/x/w/goroot/src/runtime/chanbarrier_test.go:53 +0x2c fp=0xc0002c5f30 sp=0xc0002c5f08 pc=0x36b55c
testing.tRunner(0xc0003f8540, 0x587b90)
	/home/swarming/.swarming/w/ir/x/w/goroot/src/testing/testing.go:1931 +0x108 fp=0xc0002c5f90 sp=0xc0002c5f30 pc=0x148ee8
testing.(*T).Run.gowrap1()
	/home/swarming/.swarming/w/ir/x/w/goroot/src/testing/testing.go:1994 +0x50 fp=0xc0002c5fc0 sp=0xc0002c5f90 pc=0x149f30
runtime.goexit({})
	/home/swarming/.swarming/w/ir/x/w/goroot/src/runtime/asm_ppc64x.s:1015 +0x4 fp=0xc0002c5fc0 sp=0xc0002c5fc0 pc=0xa9924
created by testing.(*T).Run in goroutine 1
	/home/swarming/.swarming/w/ir/x/w/goroot/src/testing/testing.go:1994 +0x43c

— watchflakes