[issue26839] Python 3.5 running on Linux kernel 3.17+ can block at startup or on importing the random module on getrandom()

[Colm Buckley]

Colm Buckley added the comment:

@larry -

Thank you for joining in. I'm uploading a third version of the patch (against clean 3.5.1 source, with correct whitespace and a less confusing comment) which implements the following:

* configure.ac / pyconfig.h.in : looks for linux/random.h and sets HAVE_LINUX_RANDOM_H if present.

* random.c : calls getrandom() with the GRND_NONBLOCK flag; if that fails, fall back to reading /dev/urandom which will have insufficient entropy but will at least return some data.

I feel that there is no consistent way to signal to higher-level applications that the random data has sub-standard entropy; but that this at least preserves the expected semantics, and doesn't block on startup in the event of an uninitialized entropy pool.

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Added file: http://bugs.python.org/file43265/getrandom-nonblocking-v3.patch

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