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SubjectRe: [PATCH v4 5/6] coresight: Set and clear sink device handler for kdump node
On Fri, Mar 30, 2018 at 11:15:23AM +0800, Leo Yan wrote:
> If Coresight path is enabled for specific CPU, the sink device handler
> need to be set to kdump node; on the other hand we also need to clear
> sink device handler when path is disabled.
>
> This patch sets sink devices handler for kdump node for two separate
> Coresight enabling modes: CS_MODE_SYSFS and CS_MODE_PERF; and clear the
> handler when Coresight is disabled.
>
> Signed-off-by: Leo Yan <leo.yan@linaro.org>
> ---
> drivers/hwtracing/coresight/coresight-etm-perf.c | 5 +++++
> drivers/hwtracing/coresight/coresight.c | 16 ++++++++++++++--
> 2 files changed, 19 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/hwtracing/coresight/coresight-etm-perf.c b/drivers/hwtracing/coresight/coresight-etm-perf.c
> index 8a0ad77..f8b159c 100644
> --- a/drivers/hwtracing/coresight/coresight-etm-perf.c
> +++ b/drivers/hwtracing/coresight/coresight-etm-perf.c
> @@ -139,6 +139,8 @@ static void free_event_data(struct work_struct *work)
> for_each_cpu(cpu, mask) {
> if (!(IS_ERR_OR_NULL(event_data->path[cpu])))
> coresight_release_path(event_data->path[cpu]);
> +
> + coresight_kdump_sink(cpu, NULL);
> }
>
> kfree(event_data->path);
> @@ -238,6 +240,9 @@ static void *etm_setup_aux(int event_cpu, void **pages,
> event_data->path[cpu] = coresight_build_path(csdev, sink);
> if (IS_ERR(event_data->path[cpu]))
> goto err;
> +
> + if (coresight_kdump_sink(cpu, sink))
> + goto err;

I remember telling you to use free_event_data() and etm_setup_aux(). _Maybe_ it
made sense in the previous patchset but in this one it won't work. We need to
reflect the current trace context, as such use etm_event_start() and
etm_event_stop().

In etm_event_start() call coresight_kdump_sink(cpu, sink) just before
source_ops(csdev)->enable(). Similarly call coresight_kdump_sink(cpu, NULL)
right after source_ops(csdev)->disable() in etm_event_stop().

Find me on IRC if you want more information on this.

> }
>
> if (!sink_ops(sink)->alloc_buffer)
> diff --git a/drivers/hwtracing/coresight/coresight.c b/drivers/hwtracing/coresight/coresight.c
> index 389c4ba..483a1f7 100644
> --- a/drivers/hwtracing/coresight/coresight.c
> +++ b/drivers/hwtracing/coresight/coresight.c
> @@ -272,6 +272,7 @@ static int coresight_enable_source(struct coresight_device *csdev, u32 mode)
> static bool coresight_disable_source(struct coresight_device *csdev)
> {
> if (atomic_dec_return(csdev->refcnt) == 0) {
> +

This newline shouldn't be part of this set.

> if (source_ops(csdev)->disable)
> source_ops(csdev)->disable(csdev, NULL);
> csdev->enable = false;
> @@ -612,6 +613,13 @@ int coresight_enable(struct coresight_device *csdev)
> if (ret)
> goto err_source;
>
> + cpu = source_ops(csdev)->cpu_id(csdev);
> +
> + /* Set sink device handler into kdump node */
> + ret = coresight_kdump_sink(cpu, sink);
> + if (ret)
> + goto err_kdump;
> +

Call coresight_kdump_sink() just before coresight_enable_source(). That way if
there is a dump just after coresight_enable_source() is called we get the chance
of getting some traces in the dump file.

> switch (subtype) {
> case CORESIGHT_DEV_SUBTYPE_SOURCE_PROC:
> /*
> @@ -621,7 +629,6 @@ int coresight_enable(struct coresight_device *csdev)
> * be a single session per tracer (when working from sysFS)
> * a per-cpu variable will do just fine.
> */
> - cpu = source_ops(csdev)->cpu_id(csdev);
> per_cpu(tracer_path, cpu) = path;
> break;
> case CORESIGHT_DEV_SUBTYPE_SOURCE_SOFTWARE:
> @@ -636,6 +643,9 @@ int coresight_enable(struct coresight_device *csdev)
> mutex_unlock(&coresight_mutex);
> return ret;
>
> +err_kdump:
> + coresight_disable_source(csdev);
> +
> err_source:
> coresight_disable_path(path);
>
> @@ -659,9 +669,10 @@ void coresight_disable(struct coresight_device *csdev)
> if (!csdev->enable || !coresight_disable_source(csdev))
> goto out;
>
> + cpu = source_ops(csdev)->cpu_id(csdev);
> +
> switch (csdev->subtype.source_subtype) {
> case CORESIGHT_DEV_SUBTYPE_SOURCE_PROC:
> - cpu = source_ops(csdev)->cpu_id(csdev);
> path = per_cpu(tracer_path, cpu);
> per_cpu(tracer_path, cpu) = NULL;
> break;
> @@ -674,6 +685,7 @@ void coresight_disable(struct coresight_device *csdev)
> break;
> }
>
> + coresight_kdump_sink(cpu, NULL);
> coresight_disable_path(path);
> coresight_release_path(path);
>
> --
> 2.7.4
>

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