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SubjectRe: [PATCH v3 1/2] media: usb: pwc: Introduce TRACE_EVENTs for pwc_isoc_handler()
On Thu,  9 Aug 2018 12:33:06 +0300
"Matwey V. Kornilov" <matwey@sai.msu.ru> wrote:

> There were reports that PWC-based webcams don't work at some
> embedded ARM platforms. [1] Isochronous transfer handler seems to
> work too long leading to the issues in MUSB USB host subsystem.
> Also note, that urb->giveback() handlers are still called with
> disabled interrupts. In order to be able to measure performance of
> PWC driver, traces are introduced in URB handler section.
>
> [1] https://www.spinics.net/lists/linux-usb/msg165735.html
>
> Signed-off-by: Matwey V. Kornilov <matwey@sai.msu.ru>
> ---
> drivers/media/usb/pwc/pwc-if.c | 7 +++++
> include/trace/events/pwc.h | 64 ++++++++++++++++++++++++++++++++++++++++++
> 2 files changed, 71 insertions(+)
> create mode 100644 include/trace/events/pwc.h
>
> diff --git a/drivers/media/usb/pwc/pwc-if.c b/drivers/media/usb/pwc/pwc-if.c
> index 54b036d39c5b..72d2897a4b9f 100644
> --- a/drivers/media/usb/pwc/pwc-if.c
> +++ b/drivers/media/usb/pwc/pwc-if.c
> @@ -76,6 +76,9 @@
> #include "pwc-dec23.h"
> #include "pwc-dec1.h"
>
> +#define CREATE_TRACE_POINTS
> +#include <trace/events/pwc.h>
> +
> /* Function prototypes and driver templates */
>
> /* hotplug device table support */
> @@ -260,6 +263,8 @@ static void pwc_isoc_handler(struct urb *urb)
> int i, fst, flen;
> unsigned char *iso_buf = NULL;
>
> + trace_pwc_handler_enter(urb, pdev);
> +
> if (urb->status == -ENOENT || urb->status == -ECONNRESET ||
> urb->status == -ESHUTDOWN) {
> PWC_DEBUG_OPEN("URB (%p) unlinked %ssynchronously.\n",
> @@ -348,6 +353,8 @@ static void pwc_isoc_handler(struct urb *urb)
> }
>
> handler_end:
> + trace_pwc_handler_exit(urb, pdev);
> +
> i = usb_submit_urb(urb, GFP_ATOMIC);
> if (i != 0)
> PWC_ERROR("Error (%d) re-submitting urb in pwc_isoc_handler.\n", i);
> diff --git a/include/trace/events/pwc.h b/include/trace/events/pwc.h
> new file mode 100644
> index 000000000000..71ba98770537
> --- /dev/null
> +++ b/include/trace/events/pwc.h
> @@ -0,0 +1,64 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +#if !defined(_TRACE_PWC_H) || defined(TRACE_HEADER_MULTI_READ)
> +#define _TRACE_PWC_H
> +
> +#include <linux/usb.h>
> +#include <linux/tracepoint.h>
> +
> +#undef TRACE_SYSTEM
> +#define TRACE_SYSTEM pwc
> +
> +TRACE_EVENT(pwc_handler_enter,
> + TP_PROTO(struct urb *urb, struct pwc_device *pdev),
> + TP_ARGS(urb, pdev),
> + TP_STRUCT__entry(
> + __field(struct urb*, urb)
> + __field(int, urb__status)
> + __field(u32, urb__actual_length)
> + __field(const char*, name)

name needs to be a __string. Never save pointers that you will
dereference in the print_fmt, as you never know if those pointers will
exist later. Not to mention, userspace tools like trace-cmd and perf
have no idea how to display them.

You want:

__string( name, pdev->v4l2_dev.name ),


> + __field(struct pwc_frame_buf*, fbuf)
> + __field(int, fbuf__filled)
> + ),
> + TP_fast_assign(
> + __entry->urb = urb;
> + __entry->urb__status = urb->status;
> + __entry->urb__actual_length = urb->actual_length;
> + __entry->name = pdev->v4l2_dev.name;

And here you assign it with:

__assign_str(name, pdev->v4l2_dev.name);

> + __entry->fbuf = pdev->fill_buf;
> + __entry->fbuf__filled = (pdev->fill_buf ? pdev->fill_buf->filled : 0);
> + ),
> + TP_printk("dev=%s (fbuf=%p filled=%d) urb=%p (status=%d actual_length=%u)",
> + __entry->name,

And display it with:

__get_str(name),

> + __entry->fbuf,
> + __entry->fbuf__filled,
> + __entry->urb,
> + __entry->urb__status,
> + __entry->urb__actual_length)
> +);
> +
> +TRACE_EVENT(pwc_handler_exit,
> + TP_PROTO(struct urb *urb, struct pwc_device* pdev),
> + TP_ARGS(urb, pdev),
> + TP_STRUCT__entry(
> + __field(struct urb*, urb)
> + __field(const char*, name)
> + __field(struct pwc_frame_buf*, fbuf)
> + __field(int, fbuf__filled)
> + ),
> + TP_fast_assign(
> + __entry->urb = urb;
> + __entry->name = pdev->v4l2_dev.name;
> + __entry->fbuf = pdev->fill_buf;
> + __entry->fbuf__filled = pdev->fill_buf->filled;
> + ),
> + TP_printk(" dev=%s (fbuf=%p filled=%d) urb=%p",
> + __entry->name,

Same thing here.

-- Steve

> + __entry->fbuf,
> + __entry->fbuf__filled,
> + __entry->urb)
> +);
> +
> +#endif /* _TRACE_PWC_H */
> +
> +/* This part must be outside protection */
> +#include <trace/define_trace.h>

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