linux-kernel - Re: [PATCH] ftrace: properly merge notrace hash

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Message-ID: <CAFTtA3N=fB9Yr3EiTUpGzF2imtwgnVEextyL3+V1wiTJ_jp+WA@mail.gmail.com>
Date: Tue, 8 Apr 2025 23:55:19 +0800
From: Andy Chiu <andybnac@...il.com>
To: Steven Rostedt <rostedt@...dmis.org>
Cc: linux-kernel@...r.kernel.org, linux-trace-kernel@...r.kernel.org, 
	mark.rutland@....com, mhiramat@...nel.org, mathieu.desnoyers@...icios.com, 
	bjorn@...osinc.com, puranjay12@...il.com, alexghiti@...osinc.com, 
	paul.walmsley@...ive.com, greentime.hu@...ive.com, nick.hu@...ive.com, 
	nylon.chen@...ive.com, eric.lin@...ive.com, zong.li@...ive.com, 
	yongxuan.wang@...ive.com, samuel.holland@...ive.com, olivia.chu@...ive.com, 
	c2232430@...il.com, vincent.chen@...ive.com
Subject: Re: [PATCH] ftrace: properly merge notrace hash

Steven Rostedt <rostedt@...dmis.org> 於 2025年4月8日 週二 上午4:08寫道：
>
> On Tue,  8 Apr 2025 02:07:44 +0800
> Andy Chiu <andybnac@...il.com> wrote:
>
> > The global notrace hash should be jointly decided by the intersection of
> > each subops's notrace hash, but not the filter hash.
> >
> > Fixes: 5fccc7552ccb ("ftrace: Add subops logic to allow one ops to manage many")
> > Signed-off-by: Andy Chiu <andybnac@...il.com>
> > ---
> >  kernel/trace/ftrace.c | 11 +++++------
> >  1 file changed, 5 insertions(+), 6 deletions(-)
> >
> > diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
> > index 1a48aedb5255..ee662f380b61 100644
> > --- a/kernel/trace/ftrace.c
> > +++ b/kernel/trace/ftrace.c
> > @@ -3526,18 +3526,17 @@ int ftrace_startup_subops(struct ftrace_ops *ops, struct ftrace_ops *subops, int
> >           ftrace_hash_empty(subops->func_hash->notrace_hash)) {
> >               notrace_hash = EMPTY_HASH;
> >       } else {
> > -             size_bits = max(ops->func_hash->filter_hash->size_bits,
> > -                             subops->func_hash->filter_hash->size_bits);
> > +             size_bits = max(ops->func_hash->notrace_hash->size_bits,
> > +                             subops->func_hash->notrace_hash->size_bits);
> >               notrace_hash = alloc_ftrace_hash(size_bits);
> >               if (!notrace_hash) {
> > -                     free_ftrace_hash(filter_hash);
> > +                     free_ftrace_hash(notrace_hash);
> >                       return -ENOMEM;
> >               }
> >
> > -             ret = intersect_hash(&notrace_hash, ops->func_hash->filter_hash,
> > -                                  subops->func_hash->filter_hash);
> > +             ret = intersect_hash(&notrace_hash, ops->func_hash->notrace_hash,
> > +                                  subops->func_hash->notrace_hash);
>
> Thanks for catching this.
>
>
> >               if (ret < 0) {
> > -                     free_ftrace_hash(filter_hash);
>
> The filter_hash still needs to be freed, as it could have been allocated in
> the previous if statement and never used (both the filter_hash and
> notrace_hash get used at the end of the function via ftrace_update_ops().
>
> Care to send a v2?

Yes, thanks for reminding! Let me send a v2 with filter_hash freed on
this condition.

Regards,
Andy