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Date: Fri, 4 Apr 2025 09:58:41 -0400
From: Steven Rostedt <rostedt@goodmis.org>
To: LKML <linux-kernel@vger.kernel.org>, Linux Trace Kernel
 <linux-trace-kernel@vger.kernel.org>
Cc: Masami Hiramatsu <mhiramat@kernel.org>, Mathieu Desnoyers
 <mathieu.desnoyers@efficios.com>, Tom Zanussi <zanussi@kernel.org>
Subject: Re: [PATCH] tracing: Move histogram trigger variables from stack to
 per CPU structure
Message-ID: <20250404095841.2cac7a47@gandalf.local.home>
In-Reply-To: <20250403204251.0164a4cf@gandalf.local.home>
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On Thu, 3 Apr 2025 20:42:51 -0400
Steven Rostedt <rostedt@goodmis.org> wrote:

> +static struct hist_pad *get_hist_pad(void)
> +{
> +	struct hist_pad *hist_pad;
> +	int cnt;
> +
> +	preempt_disable();
> +	hist_pad = per_cpu_ptr(hist_pads, smp_processor_id());
> +	if (!hist_pad)
> +		goto out_fail;

Hmm, this is incorrect. hist_pads can be NULL or allocated, so the check
should be:

	if (!hist_pads)
		goto fail;
	hist_pad = per_cpu_ptr(hist_pads, smp_processor_id());

Will send v2.

-- Steve


> +
> +	if (this_cpu_read(hist_pad_cnt) == MAX_HIST_CNT)
> +		goto out_fail;
> +
> +	cnt = this_cpu_inc_return(hist_pad_cnt) - 1;
> +
> +	return &hist_pad[cnt];
> +