x/tools/gopls/internal/lsp/cache: data race in overlayFS methods

[gopherbot]

#!watchflakes
post <- pkg ~ `^golang\.org/x/tools/gopls/` && log ~ `WARNING: DATA RACE` && log ~ `^\s+golang\.org/x/tools/gopls/internal/lsp/cache\.\(\*overlayFS\)`

Issue created automatically to collect these failures.

Example (log):

--- FAIL: TestLinks (9.94s)
    integration_test.go:436: gopls links a.go: exited with code 66, want 0 (gopls links a.go: exit=66 stdout=<<https://pkg.go.dev/
        https://go.dev/cl
        https://blog.go.dev/
        >> stderr=<<==================
        WARNING: DATA RACE
        Write at 0x00c000560090 by main goroutine:
          runtime.mapassign_faststr()
              /tmp/workdir/go/src/runtime/map_faststr.go:203 +0x0
          golang.org/x/tools/gopls/internal/lsp/cache.(*overlayFS).updateOverlays()
...
              /tmp/workdir/gopath/src/golang.org/x/tools/internal/tool/tool.go:92 +0x225
          golang.org/x/tools/gopls/internal/lsp/cmd/test.goplsMain()
              /tmp/workdir/gopath/src/golang.org/x/tools/gopls/internal/lsp/cmd/test/integration_test.go:766 +0xe4
          golang.org/x/tools/gopls/internal/lsp/cmd/test.TestMain()
              /tmp/workdir/gopath/src/golang.org/x/tools/gopls/internal/lsp/cmd/test/integration_test.go:757 +0x55
          main.main()
              _testmain.go:83 +0x317
        ==================
        Found 1 data race(s)
        >>)

— watchflakes

[gopherbot]

Found new dashboard test flakes for:

#!watchflakes
post <- pkg == "golang.org/x/tools/gopls/internal/lsp/cmd/test" && test == "TestLinks"

2023-01-30 20:26 freebsd-amd64-race tools@87d00e63 go@581603cb x/tools/gopls/internal/lsp/cmd/test.TestLinks (log)

--- FAIL: TestLinks (9.94s)
    integration_test.go:436: gopls links a.go: exited with code 66, want 0 (gopls links a.go: exit=66 stdout=<<https://pkg.go.dev/
        https://go.dev/cl
        https://blog.go.dev/
        >> stderr=<<==================
        WARNING: DATA RACE
        Write at 0x00c000560090 by main goroutine:
          runtime.mapassign_faststr()
              /tmp/workdir/go/src/runtime/map_faststr.go:203 +0x0
          golang.org/x/tools/gopls/internal/lsp/cache.(*overlayFS).updateOverlays()
...
              /tmp/workdir/gopath/src/golang.org/x/tools/internal/tool/tool.go:92 +0x225
          golang.org/x/tools/gopls/internal/lsp/cmd/test.goplsMain()
              /tmp/workdir/gopath/src/golang.org/x/tools/gopls/internal/lsp/cmd/test/integration_test.go:766 +0xe4
          golang.org/x/tools/gopls/internal/lsp/cmd/test.TestMain()
              /tmp/workdir/gopath/src/golang.org/x/tools/gopls/internal/lsp/cmd/test/integration_test.go:757 +0x55
          main.main()
              _testmain.go:83 +0x317
        ==================
        Found 1 data race(s)
        >>)

— watchflakes

[gopherbot]

Found new dashboard test flakes for:

#!watchflakes
post <- pkg == "golang.org/x/tools/gopls/internal/lsp/cmd/test" && test == "TestLinks"

2023-01-30 20:48 freebsd-amd64-race tools@d1e92d6a go@581603cb x/tools/gopls/internal/lsp/cmd/test.TestLinks (log)

--- FAIL: TestLinks (23.86s)
    integration_test.go:444: gopls links -json a.go: exited with code 66, want 0 (gopls links -json a.go: exit=66 stdout=<<[
        	{
        		"range": {
        			"start": {
        				"line": 0,
        				"character": 24
        			},
        			"end": {
        				"line": 0,
...
              /tmp/workdir/gopath/src/golang.org/x/tools/internal/tool/tool.go:92 +0x225
          golang.org/x/tools/gopls/internal/lsp/cmd/test.goplsMain()
              /tmp/workdir/gopath/src/golang.org/x/tools/gopls/internal/lsp/cmd/test/integration_test.go:766 +0xe4
          golang.org/x/tools/gopls/internal/lsp/cmd/test.TestMain()
              /tmp/workdir/gopath/src/golang.org/x/tools/gopls/internal/lsp/cmd/test/integration_test.go:757 +0x55
          main.main()
              _testmain.go:83 +0x317
        ==================
        Found 1 data race(s)
        >>)

— watchflakes

[bcmills]

(attn @findleyr @adonovan)