linux-kernel - [PATCH 5.10 078/135] tracepoint: static call: Compare data on transition from 2->1 callees

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Message-Id: <20210810172958.382412734@linuxfoundation.org>
Date:   Tue, 10 Aug 2021 19:30:12 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Ingo Molnar <mingo@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        "Paul E. McKenney" <paulmck@...nel.org>,
        Stefan Metzmacher <metze@...ba.org>,
        Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
        "Steven Rostedt (VMware)" <rostedt@...dmis.org>
Subject: [PATCH 5.10 078/135] tracepoint: static call: Compare data on transition from 2->1 callees

From: Mathieu Desnoyers <mathieu.desnoyers@...icios.com>

commit f7ec4121256393e1d03274acdca73eb18958f27e upstream.

On transition from 2->1 callees, we should be comparing .data rather
than .func, because the same callback can be registered twice with
different data, and what we care about here is that the data of array
element 0 is unchanged to skip rcu sync.

Link: https://lkml.kernel.org/r/20210805132717.23813-2-mathieu.desnoyers@efficios.com
Link: https://lore.kernel.org/io-uring/4ebea8f0-58c9-e571-fd30-0ce4f6f09c70@samba.org/

Cc: stable@...r.kernel.org
Cc: Ingo Molnar <mingo@...hat.com>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Andrew Morton <akpm@...ux-foundation.org>
Cc: "Paul E. McKenney" <paulmck@...nel.org>
Cc: Stefan Metzmacher <metze@...ba.org>
Fixes: 547305a64632 ("tracepoint: Fix out of sync data passing by static caller")
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
Signed-off-by: Steven Rostedt (VMware) <rostedt@...dmis.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 kernel/tracepoint.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/kernel/tracepoint.c
+++ b/kernel/tracepoint.c
@@ -359,7 +359,7 @@ static int tracepoint_remove_func(struct
 	} else {
 		rcu_assign_pointer(tp->funcs, tp_funcs);
 		tracepoint_update_call(tp, tp_funcs,
-				       tp_funcs[0].func != old[0].func);
+				       tp_funcs[0].data != old[0].data);
 	}
 	release_probes(old);
 	return 0;