Arch Linux

Description:

The counter used for generating async operation ids was a plain int
shared between all ports, which was incorrect but mostly worked
fine since the ids only had to be unique on a per-port basis.
However, some compilers (notably GCC 8.1.1) generated code that
assumed that this value didn't change between reads. Using a
shortened version of enq_async_w_tmo as an example:

int id = async_ref++;
op->id = id; //A
return id; //B

In GCC 7 and earlier, `async_ref` would be read once and assigned
to `id` before being incremented, which kept the values at A and B
consistent. In GCC 8, `async_ref` was read when assigned at A and
read again at B, and then incremented, which made them inconsistent
if we raced with another port.

The issue is fixed upstream in 21.0.2.

Additional info:
* package version(s)

erlang 21.0.1-*
erlang-nox 21.0.1-*

* config and/or log files etc.

nil

Steps to reproduce:

references:

[1]: https://github.com/elixir-ecto/db_connection/issues/127
[2]: https://github.com/jhogberg/otp/commit/e27b98b353df6b4d02d0180fd6ffa86519b41917