linux-kernel - RE: [PATCH] cxl/mbox: Fix debug message print

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Date:   Mon, 31 Jul 2023 15:12:42 -0700
From:   Dan Williams <dan.j.williams@...el.com>
To:     Ira Weiny <ira.weiny@...el.com>,
        Davidlohr Bueso <dave@...olabs.net>,
        Jonathan Cameron <jonathan.cameron@...wei.com>,
        Dave Jiang <dave.jiang@...el.com>,
        Alison Schofield <alison.schofield@...el.com>,
        "Vishal Verma" <vishal.l.verma@...el.com>,
        Dan Williams <dan.j.williams@...el.com>
CC:     Jonathan Cameron <Jonathan.Cameron@...wei.com>,
        <linux-cxl@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        Ira Weiny <ira.weiny@...el.com>
Subject: RE: [PATCH] cxl/mbox: Fix debug message print

Ira Weiny wrote:
> The handle value used to report an event being cleared by dev_dbg() is
> incorrect due to a post increment of the payload handle index.
> 
> Delay the increment of the index until after the print.  Also add the
> debugging for event processing which was useful in finding this bug.
> 
> To: Davidlohr Bueso <dave@...olabs.net>
> To: Jonathan Cameron <jonathan.cameron@...wei.com>
> To: Dave Jiang <dave.jiang@...el.com>
> To: Alison Schofield <alison.schofield@...el.com>
> To: Vishal Verma <vishal.l.verma@...el.com>
> To: Dan Williams <dan.j.williams@...el.com>

Is this some new process recommendation to use "To:", I would only
expect Cc: for maintainers.

> Cc: Jonathan Cameron <Jonathan.Cameron@...wei.com>

Jonathan gets listed twice because?

> Cc: linux-cxl@...r.kernel.org
> Cc: linux-kernel@...r.kernel.org

I assume this is because b4 takes its address from the patch itself?

It just feels a bit too noisy.

> Signed-off-by: Ira Weiny <ira.weiny@...el.com>
> ---
> NOTE: This does fix a bug in the patch referenced below.  However, I
> don't think that warrants back porting because this is only a debug
> print.

I don't think that's a reason not to flag for backport. Smaller things
than this have been backported, and if it saves someone getting confused
in the field its worth it.

> 
> Fixes: 6ebe28f9ec72 ("cxl/mem: Read, trace, and clear events on driver load")
> ---
>  drivers/cxl/core/mbox.c | 9 +++++++--
>  1 file changed, 7 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/cxl/core/mbox.c b/drivers/cxl/core/mbox.c
> index d6d067fbee97..f052d5f174ee 100644
> --- a/drivers/cxl/core/mbox.c
> +++ b/drivers/cxl/core/mbox.c
> @@ -882,9 +882,10 @@ static int cxl_clear_event_record(struct cxl_memdev_state *mds,
>  	 */
>  	i = 0;
>  	for (cnt = 0; cnt < total; cnt++) {
> -		payload->handles[i++] = get_pl->records[cnt].hdr.handle;
> +		payload->handles[i] = get_pl->records[cnt].hdr.handle;
>  		dev_dbg(mds->cxlds.dev, "Event log '%d': Clearing %u\n", log,
>  			le16_to_cpu(payload->handles[i]));
> +		i++;
>  
>  		if (i == max_handles) {
>  			payload->nr_recs = i;
> @@ -946,9 +947,13 @@ static void cxl_mem_get_records_log(struct cxl_memdev_state *mds,
>  		if (!nr_rec)
>  			break;
>  
> -		for (i = 0; i < nr_rec; i++)
> +		for (i = 0; i < nr_rec; i++) {
> +			dev_dbg(dev, "Event log %d: processing handle %u\n",
> +				type,
> +				le16_to_cpu(payload->records[i].hdr.handle));
>  			cxl_event_trace_record(cxlmd, type,
>  					       &payload->records[i]);

This looks unrelated to the fix.

> +		}
>  
>  		if (payload->flags & CXL_GET_EVENT_FLAG_OVERFLOW)
>  			trace_cxl_overflow(cxlmd, type, payload);
> 
> ---
> base-commit: 5d0c230f1de8c7515b6567d9afba1f196fb4e2f4
> change-id: 20230731-cxl-fix-clear-event-debug-print-3b57da0e956c
> 
> Best regards,
> -- 
> Ira Weiny <ira.weiny@...el.com>
>