linux-kernel - Re: [PATCH v5] tracepoint: Do not fail unregistering a probe due to memory failure

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Message-ID: <20210130094211.719f03a6@oasis.local.home>
Date:   Sat, 30 Jan 2021 09:42:11 -0500
From:   Steven Rostedt <rostedt@...dmis.org>
To:     Alexey Kardashevskiy <aik@...abs.ru>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
        Matt Mullins <mmullins@...x.us>, paulmck <paulmck@...nel.org>,
        Ingo Molnar <mingo@...hat.com>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        Martin KaFai Lau <kafai@...com>,
        Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>,
        Andrii Nakryiko <andriin@...com>,
        John Fastabend <john.fastabend@...il.com>,
        KP Singh <kpsingh@...omium.org>,
        Kees Cook <keescook@...omium.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Josh Poimboeuf <jpoimboe@...hat.com>
Subject: Re: [PATCH v5] tracepoint: Do not fail unregistering a probe due to
 memory failure

On Sat, 30 Jan 2021 09:36:26 -0500
Steven Rostedt <rostedt@...dmis.org> wrote:

> Do you still have the same crash with v3 (that's the one I'm going to
> go with for now.)
> 
>  https://lore.kernel.org/r/20201118093405.7a6d2290@gandalf.local.home

Just curious, does the following patch fix it for v5?

-- Steve

diff --git a/kernel/tracepoint.c b/kernel/tracepoint.c
index 7261fa0f5e3c..cf3a6d104fdb 100644
--- a/kernel/tracepoint.c
+++ b/kernel/tracepoint.c
@@ -306,6 +306,7 @@ static int tracepoint_remove_func(struct tracepoint *tp,
 			tp->unregfunc();
 
 		static_key_disable(&tp->key);
+		tracepoint_synchronize_unregister();
 		rcu_assign_pointer(tp->funcs, tp_funcs);
 	} else {
 		rcu_assign_pointer(tp->funcs, tp_funcs);