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Were there any code examples provided that show how to easily trigger races & deadlocks? I mean, the Go team needs to be aware of these problems and provide a f

Were there any code examples provided that show how to easily trigger races & deadlocks? I mean, the Go team needs to be aware of these problems and provide a fix or something.

Jweb_Guru 12y ago
The issues weren't with Go--which definitely allows for both data races and deadlocks and doesn't claim to eliminate either--but with etcd. And according to aphyr, the team was very responsive and quickly fixed the ones he found. My point wasn't that Go is _worse_ than contemporary languages like C++ and Java when it comes to data races, only that it doesn't eliminate them. Which, again, it doesn't claim to. Rust does, and it is an important difference between the two languages. Because data race freedom with cheap mutable state requires a garbage-collection free subset of your language [1], I think it's unlikely that Go will ever guarantee this. [1] as noted by Niko Matsakis at http://smallcultfollowing.com/babysteps/blog/2013/06/11/on-the-connection-between-memory-management-and-data-race-freedom/ http://smallcultfollowing.com/babysteps/blog/2013/06/11/on-t...
rdtsc 12y ago
> show how to easily trigger races & deadlocks? I mean, the Go team needs to be aware of these problems and provide a fix or something. You mean file a bug like "issue #1935 -- stop sharing memory between goroutines" (I just made it up to be silly there is no such bug report) In other words, they have explicitly designed in the ability to share memory between goroutines. You can certainly file an issue or bug report about, somehow I doubt that will lead to much but being kickout and laughed at. One can also just have 2 goroutines wait on each for results and that's a deadlock. Maybe there is a tool to detect that would be nice. Do you know of one?
- NateDad 12y ago
  If all goroutines deadlock, then the runtime will panic and you'll get stack traces for everything. But yes, you can obviously deadlock one or more goroutines trivially. A simple select{} will just block one goroutine forever, for example. And no, there's no tools currently that will detect deadlocks, AFAIK.
  - malkia 12y ago
    I haven't looked into that (or googled), but how does one detect that everything has deadlocked - is it some kind of profiling/sampling being done, or is it something more system specific? Any pointers? Thanks!
    - f2f 12y ago
      "all goroutines are asleep - deadlock". https://code.google.com/p/go/source/browse/src/runtime/proc.c#2757 https://code.google.com/p/go/source/browse/src/runtime/proc....
    - jesstaa 12y ago
      http://golang.org/pkg/runtime/pprof/#Profile http://golang.org/pkg/runtime/pprof/#Profile Provides a "blocking profile" that tells you what things blocked and for how long they blocked for. You can use it to find places where you've deadlocked as well as places where adding buffered channels might help performance.
  - mutation 12y ago
    It seems that Go's race detector (https://blog.golang.org/race-detector https://blog.golang.org/race-detector) can do that. see an example: http://pastie.org/9705392 http://pastie.org/9705392

Were there any code examples provided that show how to easily trigger races & deadlocks? I mean, the Go team needs to be aware of these problems and provide a fix or something.

Jweb_Guru 12y ago

The issues weren't with Go--which definitely allows for both data races and deadlocks and doesn't claim to eliminate either--but with etcd. And according to aphyr, the team was very responsive and quickly fixed the ones he found. My point wasn't that Go is _worse_ than contemporary languages like C++ and Java when it comes to data races, only that it doesn't eliminate them. Which, again, it doesn't claim to. Rust does, and it is an important difference between the two languages. Because data race freedom with cheap mutable state requires a garbage-collection free subset of your language [1], I think it's unlikely that Go will ever guarantee this. [1] as noted by Niko Matsakis at http://smallcultfollowing.com/babysteps/blog/2013/06/11/on-the-connection-between-memory-management-and-data-race-freedom/ http://smallcultfollowing.com/babysteps/blog/2013/06/11/on-t...

rdtsc 12y ago

> show how to easily trigger races & deadlocks? I mean, the Go team needs to be aware of these problems and provide a fix or something. You mean file a bug like "issue #1935 -- stop sharing memory between goroutines" (I just made it up to be silly there is no such bug report) In other words, they have explicitly designed in the ability to share memory between goroutines. You can certainly file an issue or bug report about, somehow I doubt that will lead to much but being kickout and laughed at. One can also just have 2 goroutines wait on each for results and that's a deadlock. Maybe there is a tool to detect that would be nice. Do you know of one?

NateDad 12y ago
If all goroutines deadlock, then the runtime will panic and you'll get stack traces for everything. But yes, you can obviously deadlock one or more goroutines trivially. A simple select{} will just block one goroutine forever, for example. And no, there's no tools currently that will detect deadlocks, AFAIK.
- malkia 12y ago
  I haven't looked into that (or googled), but how does one detect that everything has deadlocked - is it some kind of profiling/sampling being done, or is it something more system specific? Any pointers? Thanks!
  - f2f 12y ago
    "all goroutines are asleep - deadlock". https://code.google.com/p/go/source/browse/src/runtime/proc.c#2757 https://code.google.com/p/go/source/browse/src/runtime/proc....
  - jesstaa 12y ago
    http://golang.org/pkg/runtime/pprof/#Profile http://golang.org/pkg/runtime/pprof/#Profile Provides a "blocking profile" that tells you what things blocked and for how long they blocked for. You can use it to find places where you've deadlocked as well as places where adding buffered channels might help performance.
- mutation 12y ago
  It seems that Go's race detector (https://blog.golang.org/race-detector https://blog.golang.org/race-detector) can do that. see an example: http://pastie.org/9705392 http://pastie.org/9705392