Can PySerial's write method be called by multiple threads?

[MRAB]

On 25/08/2010 19:36, Joel Koltner wrote:
> I have a multi-threaded application where several of the threads need to
> write to a serial port that's being handled by pySerial. If pySerial
> thread-safe in the sense that pySerial.write behaves atomically? I.e.,
> if thread 1 executes, serport.write("Hello, world!") and thread 2
> executes serport.write("All your bases are belong to us!"), is it
> guaranteed that the output over the serial port won't "mix" the two
> together (e.g., "Hello All your bases are belong to us!, world!") ?
>
> I looked at the source code, and the write method eventually boils down
> to calling an the OS's "write" function, which presumably ends up being
> a call to a C function. Given the global interpreter lock -- and
> particularly how C functions can't be interrupted by the Python
> interpreter at all -- it sure seems as though everything is copacetic here?
>
Don't assume that just because it calls a C function the GIL won't be
released. I/O calls which can take a relatively long time to complete
often release the GIL.

> If not I can just add a queue and have everything go through it, but of
> course I'd like to avoid the extra code and CPU cycles if it isn't at
> all necessary.
>
Unless I know that something is definitely thread-safe, that would be
the way I would go.