On Tue, 16 May 2023 17:47:52 +0800
Ze Gao [off-list ref] wrote:

Precisely, these that are called within kprobe_busy_{begin, end},
which the previous patch does not resolve.

Note that kprobe_busy_{begin,end} don't need to use notrace version
because kprobe itself prohibits probing on preempt_count_{add,sub}.

Thank you,

I will refine the commit message to make it clear.

FYI, details can checked out here:
    Link: https://lore.kernel.org/linux-trace-kernel/20230516132516.c902edcf21028874a74fb868@kernel.org/ (local)

Regards,
Ze

On Tue, May 16, 2023 at 5:18 PM Peter Zijlstra [off-list ref] wrote:

quoted

On Tue, May 16, 2023 at 03:18:28PM +0800, Ze Gao wrote:

quoted

Current implementation calls kprobe related functions before doing
ftrace recursion check in fprobe_kprobe_handler, which opens door
to kernel crash due to stack recursion if preempt_count_{add, sub}
is traceable.

Which preempt_count*() are you referring to? The ones you just made
_notrace in the previous patch?

-- 
Masami Hiramatsu (Google) [off-list ref]