linux-kernel - Re: [RFC PATCH 0/6] tracing: wprobe: Add wprobe for watchpoint

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Message-Id: <20250910101127.08c9602fe47b0eb18bde5897@kernel.org>
Date: Wed, 10 Sep 2025 10:11:27 +0900
From: Masami Hiramatsu (Google) <mhiramat@...nel.org>
To: Jinchao Wang <wangjinchao600@...il.com>
Cc: Steven Rostedt <rostedt@...dmis.org>, Peter Zijlstra
 <peterz@...radead.org>, Ingo Molnar <mingo@...nel.org>, x86@...nel.org,
 Mathieu Desnoyers <mathieu.desnoyers@...icios.com>, Thomas Gleixner
 <tglx@...utronix.de>, Borislav Petkov <bp@...en8.de>, Dave Hansen
 <dave.hansen@...ux.intel.com>, "H . Peter Anvin" <hpa@...or.com>, Alexander
 Shishkin <alexander.shishkin@...ux.intel.com>, Ian Rogers
 <irogers@...gle.com>, linux-kernel@...r.kernel.org,
 linux-trace-kernel@...r.kernel.org, linux-doc@...r.kernel.org,
 linux-perf-users@...r.kernel.org
Subject: Re: [RFC PATCH 0/6] tracing: wprobe: Add wprobe for watchpoint

> >> - trigger_data issue:
> >>     it appears that the instance being removed is not the same as
> >>     the one that was originally set.
> > 
> > Did you mean it will free invalid struct event_trigger_data by
> > wprobe_trigger_free(), or hw_breakpoint instance?
> > 
> > When trace_event_enable_disable(wprobe_data->file, 1, 1) at
> > wprobe_trigger_cmd_parse(), the trace_wprobe is enabled == call
> > enable_trace_wprobe(), which eventually call register_wide_hw_breakpoint()
> > with dummy address. IOW, the (wide)hw_breakpoint is allocated here.
> > 
> > When the trigger is hit, modify_wide_hw_breakpoint_local() is called
> > for updating local target address on the same hw_breakpoint.
> > So latter instance should be the same.
> In wprobe_trigger_cmd_parse(), consider removing:
>    echo '!set_wprobe:watch:dentry' >> events/fprobes/truncate/trigger
> The trigger_data passed to event_trigger_unregister() is freshly allocated.

Ah, thanks for pointing it out.
I confused to free newly allocated trigger_data instead of existing
one on the list.
Let me fix that.

Thank you,

-- 
Masami Hiramatsu (Google) <mhiramat@...nel.org>