On Thu, 14 Oct 2021 17:14:07 +0200 Petr Mladek <pmladek@xxxxxxxx> wrote: > /** > * ftrace_test_recursion_trylock - tests for recursion in same context > * > * Use this for ftrace callbacks. This will detect if the function > * tracing recursed in the same context (normal vs interrupt), > * > * Returns: -1 if a recursion happened. > - * >= 0 if no recursion > + * >= 0 if no recursion (success) > + * > + * Disables the preemption on success. It is just for a convenience. > + * Current users needed to disable the preemtion for some reasons. > */ I started replying to this explaining the difference between bit not zero and a bit zero, and I think I found a design flaw that can allow unwanted recursion. It's late and I'm about to go to bed, but I may have a new patch to fix this before this gets added, as the fix will conflict with this patch, and the fix will likely need to go to stable. Stay tuned. -- Steve
