Subject: Re: context switch within RCU read-side critical section in next-20260518+ with PREEMPT_RT

From: Bert Karwatzki <[email-masked]>
Date: Thu, 21 May 2026 13:50:48 +0200

> 
> Can you please do the following:
> 1. go back to the known crashing-tag, add my fix, verify you still get
> the amd splat and then try out the fix provided by Thomas
> 2. regardless if the above helps, can you boot a kernel built with
> CONFIG_KASAN=y
> 
> fwiw I verified my patch works fine with KASAN, including by
> intentionally miscalculating the size of the target buffer and seeing
> a nice splat from it so I'm confident I'm not corrupting anything.
> However, as there are new mallocs + free flying around at early boot,
> it is *plausible* amd was getting zeroed memory without asking for it
> and it worked by accident.

I think the warnning from amdgpu is only displayed with CONFIG_LOCKDEP=y, so
your "improved fix" does not silence the warning from amdgpu. 

The additional fix from Thomas fixes the amdgpu warning.

I also built the kernel with CONFIG_KASAN and get no error messages.

Bert Karwatzki