cmd/link: TestRandLayout failures

[gopherbot]

#!watchflakes
default <- pkg == "cmd/link" && test == "TestRandLayout"

Issue created automatically to collect these failures.

Example (log):

=== RUN   TestRandLayout
=== PAUSE TestRandLayout
=== CONT  TestRandLayout
    link_test.go:1580: seed=123: fail to run "go tool nm": exit status 1
        go tool nm: fork/exec /home/swarming/.swarming/w/ir/x/w/gocache/0b/0b2fad296cea7a87c53b7d3919f60796e74ead9ca7a808208d59f49865860744-d/nm: text file busy
--- FAIL: TestRandLayout (1.74s)

— watchflakes

[gopherbot]

Found new dashboard test flakes for:

#!watchflakes
default <- pkg == "cmd/link" && test == "TestRandLayout"

2025-08-13 22:06 gotip-linux-amd64-greenteagc go@de9b6f98 cmd/link.TestRandLayout (log)

=== RUN   TestRandLayout
=== PAUSE TestRandLayout
=== CONT  TestRandLayout
    link_test.go:1580: seed=123: fail to run "go tool nm": exit status 1
        go tool nm: fork/exec /home/swarming/.swarming/w/ir/x/w/gocache/0b/0b2fad296cea7a87c53b7d3919f60796e74ead9ca7a808208d59f49865860744-d/nm: text file busy
--- FAIL: TestRandLayout (1.74s)

— watchflakes

[gopherbot]

Found new dashboard test flakes for:

#!watchflakes
default <- pkg == "cmd/link" && test == "TestRandLayout"

2025-08-19 19:54 gotip-linux-amd64-greenteagc go@1f2e8e03 cmd/link.TestRandLayout (log)

=== RUN   TestRandLayout
=== PAUSE TestRandLayout
=== CONT  TestRandLayout
    link_test.go:1580: seed=123: fail to run "go tool nm": exit status 1
        go tool nm: fork/exec /home/swarming/.swarming/w/ir/x/w/gocache/6d/6d55de9ae0b19f18d59d4dc68eb9cc1dc0073f3c8dc44ca662488ac907750564-d/nm: text file busy
--- FAIL: TestRandLayout (1.52s)

— watchflakes

[prattmic]

cc @matloob nm is coming from the build cache. IIRC, there were previous issues fixed around cmd/go ensuring the binary is fully closed before executing?

[prattmic]

cc @golang/command-line

[matloob]

I wonder if this is due to a bug in https://go-review.googlesource.com/c/go/+/688895? We can’t run the binary from the cache if we wrote it to the cache in the same process, and we’re only supposed to force the path we wrote the file to to be reported on the first build for -n. But maybe the cached path is incorrectly being used?

[tamayika]

I'm also experiencing similar error in our CI environment after upgrading go 1.25.0.
I've never seen this error in go 1.24.x.

test2json is used concurrently to generate test result as JSON format.

[2025-08-22T06:45:19.531Z] Step #10: Failed to unmarshal JSON: go tool test2json: fork/exec /root/.cache/go-build/2e/2e7c2adf2359d50e22ba0f1862e03168f391f32372ccebc0fad0eec8b30a44b1-d/test2json: text file busy
[2025-08-22T06:45:19.531Z] Step #10: ng  	modules/xxxxxxx/yyyyyyy/zzzzzzz
[2025-08-22T06:45:19.531Z] Step #10: Failed to unmarshal JSON: go tool test2json: fork/exec /root/.cache/go-build/2e/2e7c2adf2359d50e22ba0f1862e03168f391f32372ccebc0fad0eec8b30a44b1-d/test2json: text file busy
[2025-08-22T06:45:19.531Z] Step #10: Failed to unmarshal JSON: go tool test2json: fork/exec /root/.cache/go-build/2e/2e7c2adf2359d50e22ba0f1862e03168f391f32372ccebc0fad0eec8b30a44b1-d/test2json: text file busy

[tamayika]

I found go1.25 reduced prebuilt binary.

https://tip.golang.org/doc/go1.25

The Go distribution will include fewer prebuilt tool binaries. Core toolchain binaries such as the compiler and linker will still be included, but tools not invoked by build or test operations will be built and run by go tool as needed.

This results that executing go tool test2json concurrently makes race condition between writing binary file and executing binary file especially in CI environment whose cache is always clean.
I introduced executing go tool test2json --help before executing concurrently as a workaround.
But I think go should avoid this race condition.

[gopherbot]

Found new dashboard test flakes for:

#!watchflakes
default <- pkg == "cmd/link" && test == "TestRandLayout"

2025-09-10 20:06 gotip-linux-amd64-greenteagc go@5cf8ca42 cmd/link.TestRandLayout (log)

=== RUN   TestRandLayout
=== PAUSE TestRandLayout
=== CONT  TestRandLayout
    link_test.go:1580: seed=123: fail to run "go tool nm": exit status 1
        go tool nm: fork/exec /home/swarming/.swarming/w/ir/x/w/gocache/ea/ea0e15b49a6bb704b0045f10d76c00209c70d5463e737fa6454b674a56103fff-d/nm: text file busy
--- FAIL: TestRandLayout (1.79s)

— watchflakes

[gopherbot]

Found new dashboard test flakes for:

#!watchflakes
default <- pkg == "cmd/link" && test == "TestRandLayout"

2025-09-10 20:57 gotip-linux-amd64-greenteagc go@fad1dc60 cmd/link.TestRandLayout (log)

=== RUN   TestRandLayout
=== PAUSE TestRandLayout
=== CONT  TestRandLayout
    link_test.go:1580: seed=123: fail to run "go tool nm": exit status 1
        go tool nm: fork/exec /home/swarming/.swarming/w/ir/x/w/gocache/0e/0e9d17f3853b133e56bb8e1e6af409b9fb5e67a55316c1032ae7f8dc65876ad0-d/nm: text file busy
--- FAIL: TestRandLayout (1.93s)

— watchflakes

[gopherbot]

Found new dashboard test flakes for:

#!watchflakes
default <- pkg == "cmd/link" && test == "TestRandLayout"

2025-10-15 15:32 gotip-linux-amd64-boringcrypto go@51134968 cmd/link.TestRandLayout (log)

=== RUN   TestRandLayout
=== PAUSE TestRandLayout
=== CONT  TestRandLayout
    link_test.go:1582: seed=123: fail to run "go tool nm": exit status 1
        go tool nm: fork/exec /home/swarming/.swarming/w/ir/x/w/gocache/bd/bdb7ad2d47d080e18f1c791548ece7357a6091f7dcb13416e03d7e7d8ba5ca4b-d/nm: text file busy
--- FAIL: TestRandLayout (2.83s)

— watchflakes