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SubjectRe: [PATCH v4 4/6] coresight: tmc: Hook callback for panic kdump
On Fri, Mar 30, 2018 at 11:15:22AM +0800, Leo Yan wrote:
> Since Coresight panic kdump functionality has been ready, this patch is
> to hook panic callback function for ETB/ETF driver. The driver data
> structure has allocated a buffer when the session started, so simply
> save tracing data into this buffer when panic happens and update buffer
> related info for kdump.
>
> Signed-off-by: Leo Yan <leo.yan@linaro.org>
> ---
> drivers/hwtracing/coresight/coresight-tmc-etf.c | 30 +++++++++++++++++++++++++
> 1 file changed, 30 insertions(+)
>
> diff --git a/drivers/hwtracing/coresight/coresight-tmc-etf.c b/drivers/hwtracing/coresight/coresight-tmc-etf.c
> index e2513b7..d20d546 100644
> --- a/drivers/hwtracing/coresight/coresight-tmc-etf.c
> +++ b/drivers/hwtracing/coresight/coresight-tmc-etf.c
> @@ -504,6 +504,35 @@ static void tmc_update_etf_buffer(struct coresight_device *csdev,
> CS_LOCK(drvdata->base);
> }
>
> +static void tmc_panic_cb(void *data)

I would call the function tmc_kdump_panic_cb()... That way there is absolutely
no confusion as to what it does.

> +{
> + struct coresight_device *csdev = (struct coresight_device *)data;
> + struct tmc_drvdata *drvdata = dev_get_drvdata(csdev->dev.parent);
> + unsigned long flags;
> +
> + if (WARN_ON_ONCE(drvdata->config_type != TMC_CONFIG_TYPE_ETB &&
> + drvdata->config_type != TMC_CONFIG_TYPE_ETF))
> + return;
> +
> + if (drvdata->mode == CS_MODE_DISABLED)
> + return;

This is racy - between the check and acquiring the spinlock someone may beat you
to it.

> +
> + spin_lock_irqsave(&drvdata->spinlock, flags);

if (drvdata->mode == CS_MODE_DISABLED)
goto out;

drvdata->mode = CS_MODE_DISABLED

> +
> + CS_UNLOCK(drvdata->base);
> +
> + tmc_flush_and_stop(drvdata);
> + tmc_etb_dump_hw(drvdata);
> +
> + CS_LOCK(drvdata->base);
> +
> + /* Update buffer info for panic dump */
> + csdev->kdump_buf = drvdata->buf;
> + csdev->kdump_buf_sz = drvdata->len;

out:
> +
> + spin_unlock_irqrestore(&drvdata->spinlock, flags);
> +}
> +
> static const struct coresight_ops_sink tmc_etf_sink_ops = {
> .enable = tmc_enable_etf_sink,
> .disable = tmc_disable_etf_sink,
> @@ -512,6 +541,7 @@ static const struct coresight_ops_sink tmc_etf_sink_ops = {
> .set_buffer = tmc_set_etf_buffer,
> .reset_buffer = tmc_reset_etf_buffer,
> .update_buffer = tmc_update_etf_buffer,
> + .panic_cb = tmc_panic_cb,
> };
>
> static const struct coresight_ops_link tmc_etf_link_ops = {
> --
> 2.7.4
>

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