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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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