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Date: Thu, 30 Oct 2025 19:32:06 -0700
From: Andrew Morton <akpm@linux-foundation.org>
To: Martin Kaiser <martin@kaiser.cx>
Cc: "Liam R . Howlett" <Liam.Howlett@oracle.com>,
 maple-tree@lists.infradead.org, linux-mm@kvack.org,
 linux-kernel@vger.kernel.org
Subject: Re: [PATCH] maple_tree: fix tracepoint string pointers
Message-Id: <20251030193206.22bb773e697b6cc385d5aa67@linux-foundation.org>
In-Reply-To: <20251030155537.87972-1-martin@kaiser.cx>
References: <20251030155537.87972-1-martin@kaiser.cx>
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On Thu, 30 Oct 2025 16:55:05 +0100 Martin Kaiser <martin@kaiser.cx> wrote:

> maple_tree tracepoints contain pointers to function names. Such a pointer
> is saved when a tracepoint logs an event. There's no guarantee that it's
> still valid when the event is parsed later and the pointer is dereferenced.

Oh.

> The kernel warns about these unsafe pointers.
> 
> 	event 'ma_read' has unsafe pointer field 'fn'
> 	WARNING: kernel/trace/trace.c:3779 at ignore_event+0x1da/0x1e4
> 
> Mark the function names as tracepoint_string() to fix the events.
> 
> ...
>  
> -	trace_ma_op(__func__, mas);
> +	trace_ma_op(TP_FCT, mas);
>

What could cause the storage for __func__ to disappear as you suggest?