From: Steven Rostedt <rostedt@goodmis.org>
To: David Carlier <devnexen@gmail.com>
Cc: linux-trace-kernel@vger.kernel.org, linux-kernel@vger.kernel.org,
"Vineeth Pillai (Google)" <vineeth@bitbyteword.org>,
Mathieu Desnoyers <mathieu.desnoyers@efficios.com>,
Masami Hiramatsu <mhiramat@kernel.org>,
Peter Zijlstra <peterz@infradead.org>
Subject: Re: [PATCH] tracepoint: add lockdep rcu_is_watching() check to trace_call__##name()
Date: Thu, 30 Apr 2026 09:35:54 -0400 [thread overview]
Message-ID: <20260430093554.756072d7@gandalf.local.home> (raw)
In-Reply-To: <20260430053511.8767-1-devnexen@gmail.com>
On Thu, 30 Apr 2026 06:35:10 +0100
David Carlier <devnexen@gmail.com> wrote:
> Without it, sites converted from trace_foo(args) to trace_call__foo(args)
> lose the WARN_ONCE(!rcu_is_watching()) coverage under CONFIG_LOCKDEP when
> the tracepoint is enabled - the case that commit c2679254b9c9 ("tracing:
> Make tracepoint lockdep check actually test something") added the warning
> for.
>
> Mirror the same block in both trace_call__##name() bodies, gated by
> (cond) in __DECLARE_TRACE to match its trace_##name() and ungated in
> __DECLARE_TRACE_SYSCALL.
If it gets called without rcu watching, the rcu dereference in
__DO_TRACE_CALL() will trigger.
No need to add the warning here. The reason the trace_foo() had it, was to
trigger when the tracepoint WASN'T enabled.
Now, perhaps where the warning should go, is in the trace_foo_enabled()
code.
-- Steve
next prev parent reply other threads:[~2026-04-30 13:51 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-04-30 5:35 [PATCH] tracepoint: add lockdep rcu_is_watching() check to trace_call__##name() David Carlier
2026-04-30 13:35 ` Steven Rostedt [this message]
2026-04-30 14:41 ` [PATCH v2] tracepoint: add lockdep rcu_is_watching() check to trace_##name##_enabled() David Carlier
2026-04-30 20:01 ` Steven Rostedt
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