[PATCH v3 00/13] arm64: debug: remove hook registration, split exception entry

[Ada Couprie Diaz]

On 12/06/2025 19:18, Luis Claudio R. Goncalves wrote:

> On Mon, Jun 09, 2025 at 06:34:00PM +0100, Ada Couprie Diaz wrote:
>> [...]
>>
>> PREEMPT_RT
>> ===
>>
>> Of note, this allows us to make the single exception handling mostly
>> preemptible coming from EL0 in patch 9, fixing an issue with PREEMPT_RT[0].
>> The commit message details the reasoning on why this should be safe.
>> It is *definitely* not preemptible at EL1 in the current state, given
>> that the EL1 software step exception is handled by KGDB.
>>
>> CC-ing Luis as he did a lot of testing on v2 and originally
>> reported the issue.
>>
>> Cc: "Luis Claudio R. Goncalves" <lgoncalv at redhat.com>
>>
>> We can do the same for the software break exception coming from EL0,
>> which works in a very similar way.
>>
>> However, the hardware breakpoint and watchpoint exceptions also have
>> a sleeping while non-preemptible issue with PREEMPT_RT, but this is
>> much trickier to fix, so this won't be fixed in this series.
>> A bit more details in [1].
>>
>> I hesitated to add comments within the BRK64 and single-step handlers,
>> on the EL0 paths, to highlight that they would be preemptible and to be
>> wary if modifying or adding to them, but I opted not to in the end.
>> (Partly as I didn't find a satisfactory way to do it !)
>> I would be happy to add some if anyone finds it would be beneficial.
> Tested-by: Luis Claudio R. Goncalves <lgoncalv at redhat.com>
>
> Works as advertised, fixes the reported RT problem, fails on the specific
> case Ada described above. :)
>
> Best regards,
> Luis
>
Thanks again Luis for the thorough testing and reports !

Best regards,
Ada