Re: Suspend/Resume Broken on AM43/AM33 Platforms

[Keerthy <j-keerthy@ti.com>]

On 19/08/19 11:57 AM, Stephen Boyd wrote:
> Quoting Keerthy (2019-08-18 21:24:58)
>> Hi Stephen,
>>
>> commit 03a3bb7ae63150230c5de645dc95e673ebf17e1a
>> Author: Stephen Boyd <swboyd@chromium.org>
>> Date:   Mon Aug 5 16:32:41 2019 -0700
>>
>>       hwrng: core - Freeze khwrng thread during suspend
>>
>> Commit seems to be breaking suspend/resume on TI AM43/AM33 platforms.
>>
>>
>> rtcwake: wakeup from "mem" using /dev/rtc0 at Sun Nov 18 02:12:12 2018
>> [   54.033833] PM: suspend entry (deep)
>> [   54.037741] Filesystems sync: 0.000 seconds
>> [   54.062730] Freezing user space processes ... (elapsed 0.001 seconds)
>> done.
>> [   54.071313] OOM killer disabled.
>> [   54.074572] Freezing remaining freezable tasks ...
>> [   74.083121] Freezing of tasks failed after 20.003 seconds (1 tasks
>> refusing to freeze, wq_busy=0):
>> [   74.092257] hwrng           R  running task        0   289      2
>> 0x00000020
>> [   74.099511] [<c08c64c4>] (__schedule) from [<c08c6a10>]
>> (schedule+0x3c/0xc0)
>> [   74.106720] [<c08c6a10>] (schedule) from [<c05dbd8c>]
>> (add_hwgenerator_randomness+0xb0/0x100)
>> [   74.115358] [<c05dbd8c>] (add_hwgenerator_randomness) from
>> [<bf1803c8>] (hwrng_fillfn+0xc0/0x14c [rng_core])
> 
> Thanks for the report. I suspect we need to check for freezer in
> add_hwgenerator_randomness(). I find it odd that there's another caller
> of add_hwgenerator_randomness(), but maybe the ath9k driver can be
> converted to some sort of hwrng driver instead of calling into the
> kthread directly.
> 
> Anyway, can you try this patch?

I applied the below patch on top of latest next branch.

Fixes the issue.

Thanks,
Keerthy

> 
> ---8<---
> diff --git a/drivers/char/random.c b/drivers/char/random.c
> index 5d5ea4ce1442..e2e85ca16410 100644
> --- a/drivers/char/random.c
> +++ b/drivers/char/random.c
> @@ -2429,6 +2429,7 @@ void add_hwgenerator_randomness(const char *buffer, size_t count,
>   				size_t entropy)
>   {
>   	struct entropy_store *poolp = &input_pool;
> +	bool frozen = false;
>   
>   	if (unlikely(crng_init == 0)) {
>   		crng_fast_load(buffer, count);
> @@ -2439,9 +2440,12 @@ void add_hwgenerator_randomness(const char *buffer, size_t count,
>   	 * We'll be woken up again once below random_write_wakeup_thresh,
>   	 * or when the calling thread is about to terminate.
>   	 */
> -	wait_event_interruptible(random_write_wait, kthread_should_stop() ||
> +	wait_event_interruptible(random_write_wait,
> +			kthread_freezable_should_stop(&frozen) ||
>   			ENTROPY_BITS(&input_pool) <= random_write_wakeup_bits);
> -	mix_pool_bytes(poolp, buffer, count);
> -	credit_entropy_bits(poolp, entropy);
> +	if (!frozen) {
> +		mix_pool_bytes(poolp, buffer, count);
> +		credit_entropy_bits(poolp, entropy);
> +	}
>   }
>   EXPORT_SYMBOL_GPL(add_hwgenerator_randomness);
>