Hi Daniel,
On 2022-11-09, Daniel Thompson <daniel.thomp...@linaro.org> wrote:
>> + /*
>> + * The console_srcu_read_lock() only provides safe console list
>> + * traversal. The use of the ->write() callback relies on all other
>> + * CPUs being stopped at the moment and console drivers being able to
>> + * handle reentrance when @oops_in_progress is set. (Note that there
>> + * is no guarantee for either criteria.)
>> + */
>
> The debugger entry protocol does ensure that other CPUs are either
> stopped or unresponsive. In the case where the other CPU is unresponsive
> (e.g. timed out after being asked to stop) then there is a "real" printk()
> issued prior to any of the above interference with the console system to
> the developer driving the debugger gets as much clue as we can offer them
> about what is going on (typically this is emitted from regular interrupt
> context).
>
> Given this comment is part of the debugger code then for the
> oops_in_progress hack it might be more helpful to describe what
> the developer in front the debugger needs to do to have the most
> reliable debug session possible.
>
> There is no guarantee that every console drivers can handle reentrance
> in this way; the developer deploying the debugger is responsible for
> ensuring that the console drivers they have selected handle reentrance
> appropriately.
Thanks for the explanation. I will change the comment to:
/*
* The console_srcu_read_lock() only provides safe console list
* traversal. The use of the ->write() callback relies on all other
* CPUs being stopped at the moment and console drivers being able to
* handle reentrance when @oops_in_progress is set.
*
* There is no guarantee that every console driver can handle
* reentrance in this way; the developer deploying the debugger
* is responsible for ensuring that the console drivers they
* have selected handle reentrance appropriately.
*/
John
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