On 2021/10/13 下午3:55, Miroslav Benes wrote: >> diff --git a/include/linux/trace_recursion.h b/include/linux/trace_recursion.h >> index a9f9c57..101e1fb 100644 >> --- a/include/linux/trace_recursion.h >> +++ b/include/linux/trace_recursion.h >> @@ -208,13 +208,29 @@ static __always_inline void trace_clear_recursion(int bit) >> * Use this for ftrace callbacks. This will detect if the function >> * tracing recursed in the same context (normal vs interrupt), >> * >> + * The ftrace_test_recursion_trylock() will disable preemption, >> + * which is required for the variant of synchronize_rcu() that is >> + * used to allow patching functions where RCU is not watching. >> + * See klp_synchronize_transition() for more details. >> + * > > I think that you misunderstood. Steven proposed to put the comment before > ftrace_test_recursion_trylock() call site in klp_ftrace_handler(). Oh, I see... thanks for pointing out :-) > >> * Returns: -1 if a recursion happened. [snip] >> } > > Side note... the comment will eventually conflict with peterz's > https://lore.kernel.org/all/20210929152429.125997206@xxxxxxxxxxxxx/. Steven, would you like to share your opinion on this patch? If klp_synchronize_transition() will be removed anyway, the comments will be meaningless and we can just drop it :-P Regards, Michael Wang > > Miroslav >
