[issue25420] "import random" blocks on entropy collection on Linux with low entropy

[STINNER Victor]

STINNER Victor added the comment:

Hi,

Марк Коренберг added the comment:
> Man getrandom()
>
> As of Linux 3.19, the following bug exists:
>
>        *  Depending on CPU load, getrandom() does not react to interrupts
>           before reading all bytes requested.
>
> So, is it goot to use this syscall now?

I saw a fix proposed on the LKML but it looks like it was not merged.
I don't know what to think about this bug.

getrandom(n, GRND_NONBLOCK) behaviour depends if /dev/urandom was
feeded with enough entropy and the value of n. It should not be
interrupted by signal for n <= 256.

Can you reproduce the bug? Which kind of applications can hang because
of this bug?

I would prefer to continue to use getrandom() syscall on Linux, avoid
using a file descriptor is really useful.

Maybe we can try to document the behaviour of os.urandom() for signal
handling? Or at least redirect users to getrandom() manual page.

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<http://bugs.python.org/issue25420>
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