golang protobuf APIv2 - lock on init() related to registration

[Mark Wardle]

Hi. I've upgraded to the new Go protobuf implementation (https://blog.golang.org/a-new-go-api-for-protocol-buffers) and am getting a locked thread on startup, due a lock being requested in init(). Truncated stack trace :

goroutine 1 [semacquire, locked to thread]:

sync.runtime_SemacquireMutex(0x1b137dc, 0xc0001cd700, 0x0)

/usr/local/Cellar/go/1.14/libexec/src/runtime/sema.go:71 +0x47

sync.(*RWMutex).RLock(...)

/usr/local/Cellar/go/1.14/libexec/src/sync/rwmutex.go:50

google.golang.org/protobuf/reflect/protoregistry.(*Files).FindDescriptorByName(0xc000100e50, 0xc0002147a5, 0x1c, 0x0, 0x0, 0x0, 0x0)

/Users/mark/go/src/github.com/wardle/concierge/vendor/google.golang.org/protobuf/reflect/protoregistry/registry.go:157 +0xa08

google.golang.org/protobuf/internal/impl.resolverOnly.FindDescriptorByName(0xc000100e50, 0xc0002147a5, 0x1c, 0x0, 0x0, 0x0, 0xc0002146c1)

/Users/mark/go/src/github.com/wardle/concierge/vendor/google.golang.org/protobuf/internal/impl/legacy_file.go:77 +0x3f

google.golang.org/protobuf/internal/filedesc.(*File).resolveMessageDependency(0xc000175880, 0x16fa560, 0xc000101600, 0x1, 0x135e8b1, 0xc000198ba1)

/Users/mark/go/src/github.com/wardle/concierge/vendor/google.golang.org/protobuf/internal/filedesc/desc_lazy.go:125 +0x18a

google.golang.org/protobuf/reflect/protoregistry/registry.go has this:

// This returns (nil, NotFound) if not found.

func (r *Files) FindDescriptorByName(name protoreflect.FullName) (protoreflect.Descriptor, error) {

if r == nil {

return nil, NotFound

}

if r == GlobalFiles {

globalMutex.RLock()

defer globalMutex.RUnlock()

}

prefix := name

.....

I am not sure what is going on here and not sure how to start investigating, or whether there's some incompatibility with my toolchain and module versions.

Has anyone come across this issue? Thanks,

Mark

[tandr]

Mark,

you might want to open a bug on their bug tracker.

On Wednesday, March 4, 2020 at 2:48:31 PM UTC-7, Mark Wardle wrote:

Hi. I've upgraded to the new Go protobuf implementation (https://blog.golang.org/a-new-go-api-for-protocol-buffers) and am getting a locked thread on startup, due a lock being requested in init(). Truncated stack trace :

 

<unreadable colorful stuff removed>

[Mark Wardle]

On Thursday, 5 March 2020 18:15:44 UTC, tandr wrote:

Mark,

you might want to open a bug on their bug tracker.

Will do. Thanks

 

[Mark Wardle]

So this is now fixed. For anyone else who encounters this with golang protobuf 1.20 APIv2, I modified go.mod to include the latest release from github as a temporary fix:

google.golang.org/protobuf v0.0.0-20200305173516-13e7f145cc57

instead of

google.golang.org/protobuf v1.20.0

because this deadlock fixed in commit : 

See https://github.com/protocolbuffers/protobuf-go/commit/13e7f145cc5761dc68252f725d240d04b641b01d

It's basically a deadlock on registration / initialisation of a descriptor.

Mark

[Joe Tsai]

Thanks for the bug report. This is fixed: https://github.com/protocolbuffers/protobuf-go/releases/tag/v1.20.1