Re: [PATCH v4 4/6] coresight: tmc: Hook callback for panic kdump

[Mathieu Poirier]

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 
> ---
>  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(>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(>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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[PATCH v4 4/6] coresight: tmc: Hook callback for panic kdump

[Leo Yan]

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 
---
 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)
+{
+   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;
+
+   spin_lock_irqsave(>spinlock, flags);
+
+   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;
+
+   spin_unlock_irqrestore(>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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