Kernel warning Interpretation: HW Random number Generator?

Legato Linux distribution (Yocto project)
1

I’m getting this kernel warning on my device that has been running for days:

May 9 14:27:46 swi-mdm9x15 user.warn kernel: [70106.019860] hwrng: no data available

Does anyone know what this warning is? Why do I never see this until the device is running for at least 24 hours or so? Explanation? I mean I suspect that it is related to HW Random number Generator but where does this come in here and what is it used for?

2

Which module are you using?

3

Hardware number generator is used for cryptography process(cryptographic key) which is sent with data.
Also if we need to assign any keys to any device to transmit data this can be used.
so if it shows “hwrng: no data available” means a key has not generated for driver initialization.
If board is idle for more duration it may show warning which is mentioned.It may be with release which you have flashed try flashing other firmware.

1 Like
4

@JordanZhao Mangh Green for wp85

5

So I’m seeing this warning now on my device every once in a while and the device can’t recover until a hard reset is done. @jyijyi Any suggestions?

6

what is the bad effect on this message?

7

@jyijyi When this waring appears it blocks all other Apps. I stop seeing any LOGs from my Apps and I lose the ability to be connected via data connection; nothing is uploaded to cloud anymore. I suspect that this warning is blocking all other Apps from running.

8

Any reproducible way on mangoh green board with wp85?

9

Hi
I think for temporary we can comment warning.We can change as below.
mutex_unlock(&rng_mutex);
put_rng(rng);
if (rc <= 0) {
// remove line > pr_warn(“hwrng: no data available\n”);
if (rc != -ENODEV)
pr_warn(“hwrng: no data available: %li\n”, rc);
msleep_interruptible(10000);
continue;
}

Please check with above changes.
Please check below link Linux Cryptography — Re: [PATCH] hwrng: do not warn when there are no devices