tracing/net_sched: Fix tracepoints that save qdisc_dev() as a string

I'm updating __assign_str() and will be removing the second parameter. To
make sure that it does not break anything, I make sure that it matches the
__string() field, as that is where the string is actually going to be
saved in. To make sure there's nothing that breaks, I added a WARN_ON() to
make sure that what was used in __string() is the same that is used in
__assign_str().

In doing this change, an error was triggered as __assign_str() now expects
the string passed in to be a char * value. I instead had the following
warning:

include/trace/events/qdisc.h: In function ‘trace_event_raw_event_qdisc_reset’:
include/trace/events/qdisc.h:91:35: error: passing argument 1 of 'strcmp' from incompatible pointer type [-Werror=incompatible-pointer-types]
   91 |                 __assign_str(dev, qdisc_dev(q));

That's because the qdisc_enqueue() and qdisc_reset() pass in qdisc_dev(q)
to __assign_str() and to __string(). But that function returns a pointer
to struct net_device and not a string.

It appears that these events are just saving the pointer as a string and
then reading it as a string as well.

Use qdisc_dev(q)->name to save the device instead.

Fixes: a34dac0b90552 ("net_sched: add tracepoints for qdisc_reset() and qdisc_destroy()")
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Reviewed-by: Jamal Hadi Salim <jhs@mojatatu.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/include/trace/events/qdisc.h b/include/trace/events/qdisc.h
index a3995925cb057021dc779344d19f7e3724f6df3c..1f4258308b967a9ca8e17bbf61ba4ef07b6d786b 100644 (file)
--- a/include/trace/events/qdisc.h
+++ b/include/trace/events/qdisc.h
@@ -81,14 +81,14 @@ TRACE_EVENT(qdisc_reset,
        TP_ARGS(q),
 
        TP_STRUCT__entry(
-               __string(       dev,            qdisc_dev(q)    )
-               __string(       kind,           q->ops->id      )
-               __field(        u32,            parent          )
-               __field(        u32,            handle          )
+               __string(       dev,            qdisc_dev(q)->name      )
+               __string(       kind,           q->ops->id              )
+               __field(        u32,            parent                  )
+               __field(        u32,            handle                  )
        ),
 
        TP_fast_assign(
-               __assign_str(dev, qdisc_dev(q));
+               __assign_str(dev, qdisc_dev(q)->name);
                __assign_str(kind, q->ops->id);
                __entry->parent = q->parent;
                __entry->handle = q->handle;
@@ -106,14 +106,14 @@ TRACE_EVENT(qdisc_destroy,
        TP_ARGS(q),
 
        TP_STRUCT__entry(
-               __string(       dev,            qdisc_dev(q)    )
-               __string(       kind,           q->ops->id      )
-               __field(        u32,            parent          )
-               __field(        u32,            handle          )
+               __string(       dev,            qdisc_dev(q)->name      )
+               __string(       kind,           q->ops->id              )
+               __field(        u32,            parent                  )
+               __field(        u32,            handle                  )
        ),
 
        TP_fast_assign(
-               __assign_str(dev, qdisc_dev(q));
+               __assign_str(dev, qdisc_dev(q)->name);
                __assign_str(kind, q->ops->id);
                __entry->parent = q->parent;
                __entry->handle = q->handle;