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Date: Wed, 24 Jun 2026 11:36:02 +0200
From: Greg KH <gregkh@linuxfoundation.org>
To: Wentao Guan <guanwentao@uniontech.com>
Cc: iklatzco <iklatzco@gmail.com>, 00107082 <00107082@163.com>,
	patches <patches@lists.linux.dev>, peterz <peterz@infradead.org>,
	Sasha Levin <sashal@kernel.org>, stable <stable@vger.kernel.org>,
	"yeoreum.yun" <yeoreum.yun@arm.com>
Subject: Re: perf: Fix dangling cgroup pointer in cpuctx
Message-ID: <2026062414-spry-reflux-1cd4@gregkh>
References: <20260616145120.525872058@linuxfoundation.org>
 <20260624080310.2502480-1-guanwentao@uniontech.com>
 <2026062455-obtrusive-sandbox-d6d1@gregkh>
 <tencent_62A2AD8F12114EBC582137F1@qq.com>
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In-Reply-To: <tencent_62A2AD8F12114EBC582137F1@qq.com>

On Wed, Jun 24, 2026 at 05:27:56PM +0800, Wentao Guan wrote:
> Hello,
> 
> orginal patch commit 3b7a34aebbdf2a4b7295205bf0c654294283ec82,
> perf: Fix dangling cgroup pointer in cpuctx delete
> 'event->pending_disable = 1;' in __perf_remove_from_context(),
> but the backport commit ae1ada0af16249a3ed15e33fa6719a6a2f96f537 did not.
> 
> [context different]
> 25,26c19,20
> <  kernel/events/core.c | 16 ++++------------
> <  1 file changed, 4 insertions(+), 12 deletions(-)
> ---
> >  kernel/events/core.c | 21 ++++++---------------
> >  1 file changed, 6 insertions(+), 15 deletions(-)
> 29c23
> < index 0ac83fc1cb5e3..132524d0297cb 100644
> ---
> > index 1cc98b9b3c0b4..d78608323916f 100644
> 32c26
> < @@ -2056,18 +2056,6 @@ list_del_event(struct perf_event *event, struct perf_event_context *ctx)
> ---
> > @@ -2120,18 +2120,6 @@ list_del_event(struct perf_event *event, struct perf_event_context *ctx)
> 51c45,51
> < @@ -2401,6 +2389,10 @@ __perf_remove_from_context(struct perf_event *event,
> ---
> > @@ -2488,11 +2476,14 @@ __perf_remove_from_context(struct perf_event *event,
> >               state = PERF_EVENT_STATE_EXIT;
> >       if (flags & DETACH_REVOKE)
> >               state = PERF_EVENT_STATE_REVOKED;
> > -     if (flags & DETACH_DEAD) {
> > -             event->pending_disable = 1;
> > +     if (flags & DETACH_DEAD)
> 53c53,54
> <       }
> ---
> > -     }

I'm sorry, but I can't understand un-unified diffs, and diffs of diffs
are a whole other level of toughness....  If you feel something was
backported incorrectly, can you provide a patch to fix it up?

thanks,

greg k-h