Re: [PATCH v12 4/4] usb: gadget: add configfs trace events

Greg Kroah-Hartman
2021-10-22T11:37:56Z

On Fri, Oct 22, 2021 at 09:43:06AM +0000, Linyu Yuan (QUIC) wrote:
> > From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> > Sent: Friday, October 22, 2021 5:21 PM
> > To: Linyu Yuan (QUIC) <quic_linyyuan@quicinc.com>
> > Cc: Felipe Balbi <balbi@kernel.org>; linux-usb@vger.kernel.org; Jack Pham
> > <jackp@quicinc.com>
> > Subject: Re: [PATCH v12 4/4] usb: gadget: add configfs trace events
> >
> > On Tue, Oct 19, 2021 at 09:26:37PM +0800, Linyu Yuan wrote:
> > > in case of USB Gadget functions configure through configfs from
> > > a complicated user space program, when switch function from one to
> > another,
> > > if it failed, it is better to find out what action was done to configfs
> > > from user space program.
> > >
> > > this change add some trace events which enable/disable a function,
> > > it including add/remove configuration, bind/unbind UDC,
> > > and some attribute files write operation.
> > >
> > > Suggested-by: Felipe Balbi <balbi@kernel.org>
> > > Signed-off-by: Linyu Yuan <quic_linyyuan@quicinc.com>
> > > ---
> > > v2: fix two issue Reported-by: kernel test robot <lkp@intel.com>
> > > v3: do not move private structure to configfs.h
> > > v4: add missing new file configfs_trace.h
> > > v5: lost some change of v2, add it again
> > > v6: fix comments from Greg Kroah-Hartman
> > > v7: three minor changes according to coding rules
> > > v8: change two trace location
> > > v9: fix when config is empty
> > > v10: fix wrong api in v9
> > > v11: split to 3 changes, remove read trace, change trace event print format
> > > v12: allocate trace string array per gadget driver
> > >
> > > drivers/usb/gadget/configfs.c | 17 ++++
> > > drivers/usb/gadget/configfs_trace.h | 168
> > ++++++++++++++++++++++++++++++++++++
> > > 2 files changed, 185 insertions(+)
> > > create mode 100644 drivers/usb/gadget/configfs_trace.h
> > >
> > > diff --git a/drivers/usb/gadget/configfs.c b/drivers/usb/gadget/configfs.c
> > > index 27aa569..6e7d1b1 100644
> > > --- a/drivers/usb/gadget/configfs.c
> > > +++ b/drivers/usb/gadget/configfs.c
> > > @@ -29,6 +29,7 @@ int check_user_usb_string(const char *name,
> > >
> > > #define MAX_NAME_LEN 40
> > > #define MAX_USB_STRING_LANGS 2
> > > +#define MAX_TRACE_STR_LEN 512
> > >
> > > static const struct usb_descriptor_header *otg_desc[2];
> > >
> > > @@ -51,6 +52,9 @@ struct gadget_info {
> > > char qw_sign[OS_STRING_QW_SIGN_LEN];
> > > spinlock_t spinlock;
> > > bool unbind;
> > > +#ifdef CONFIG_TRACING
> > > + char trace_string[MAX_TRACE_STR_LEN];
> > > +#endif
> > > };
> > >
> > > static inline struct gadget_info *to_gadget_info(struct config_item *item)
> > > @@ -102,6 +106,10 @@ struct gadget_config_name {
> > > struct list_head list;
> > > };
> > >
> > > +#define CONFIGFS_TRACE_STRING
> > > +#define CREATE_TRACE_POINTS
> > > +#include "configfs_trace.h"
> > > +
> > > #define USB_MAX_STRING_WITH_NULL_LEN
> > (USB_MAX_STRING_LEN+1)
> > >
> > > static int usb_string_copy(const char *s, char **s_copy)
> > > @@ -212,6 +220,7 @@ static ssize_t
> > gadget_dev_desc_bcdDevice_store(struct config_item *item,
> > >
> > > mutex_lock(&gi->lock);
> > > gi->cdev.desc.bcdDevice = cpu_to_le16(bcdDevice);
> > > + trace_gadget_dev_desc_bcdDevice_store(gi);
> > > mutex_unlock(&gi->lock);
> > > return len;
> > > }
> > > @@ -232,6 +241,7 @@ static ssize_t
> > gadget_dev_desc_bcdUSB_store(struct config_item *item,
> > >
> > > mutex_lock(&gi->lock);
> > > gi->cdev.desc.bcdUSB = cpu_to_le16(bcdUSB);
> > > + trace_gadget_dev_desc_bcdUSB_store(gi);
> > > mutex_unlock(&gi->lock);
> > > return len;
> > > }
> > > @@ -254,6 +264,7 @@ static int unregister_gadget(struct gadget_info *gi)
> > > {
> > > int ret;
> > >
> > > + trace_unregister_gadget(gi);
> > > if (!gi->composite.gadget_driver.udc_name)
> > > return -ENODEV;
> > >
> > > @@ -300,6 +311,7 @@ static ssize_t gadget_dev_desc_UDC_store(struct
> > config_item *item,
> > > goto err;
> > > }
> > > }
> > > + trace_gadget_dev_desc_UDC_store(gi);
> > > mutex_unlock(&gi->lock);
> > > return len;
> > > err:
> > > @@ -342,6 +354,7 @@ static ssize_t
> > gadget_dev_desc_max_speed_store(struct config_item *item,
> > >
> > > gi->composite.gadget_driver.max_speed = gi-
> > >composite.max_speed;
> > >
> > > + trace_gadget_dev_desc_max_speed_store(gi);
> > > mutex_unlock(&gi->lock);
> > > return len;
> > > err:
> > > @@ -465,6 +478,7 @@ static int config_usb_cfg_link(
> > > list_add_tail(&f->list, &cfg->func_list);
> > > ret = 0;
> > > out:
> > > + trace_config_usb_cfg_link(gi);
> > > mutex_unlock(&gi->lock);
> > > return ret;
> > > }
> > > @@ -496,6 +510,7 @@ static void config_usb_cfg_unlink(
> > > if (f->fi == fi) {
> > > list_del(&f->list);
> > > usb_put_function(f);
> > > + trace_config_usb_cfg_unlink(gi);
> > > mutex_unlock(&gi->lock);
> > > return;
> > > }
> > > @@ -533,6 +548,7 @@ static ssize_t
> > gadget_config_desc_MaxPower_store(struct config_item *item,
> > > return -ERANGE;
> > > mutex_lock(&gi->lock);
> > > cfg->c.MaxPower = val;
> > > + trace_gadget_config_desc_MaxPower_store(gi);
> > > mutex_unlock(&gi->lock);
> > > return len;
> > > }
> > > @@ -562,6 +578,7 @@ static ssize_t
> > gadget_config_desc_bmAttributes_store(struct config_item *item,
> > > return -EINVAL;
> > > mutex_lock(&gi->lock);
> > > cfg->c.bmAttributes = val;
> > > + trace_gadget_config_desc_bmAttributes_store(gi);
> > > mutex_unlock(&gi->lock);
> > > return len;
> > > }
> > > diff --git a/drivers/usb/gadget/configfs_trace.h
> > b/drivers/usb/gadget/configfs_trace.h
> > > new file mode 100644
> > > index 0000000..d36c61f
> > > --- /dev/null
> > > +++ b/drivers/usb/gadget/configfs_trace.h
> > > @@ -0,0 +1,168 @@
> > > +/* SPDX-License-Identifier: GPL-2.0 */
> > > +/*
> > > + * Copyright (c) 2021 Qualcomm Innovation Center, Inc. All rights reserved.
> > > + */
> > > +
> > > +#ifdef CONFIGFS_TRACE_STRING
> > > +#undef CONFIGFS_TRACE_STRING
> > > +
> > > +#ifdef CONFIG_TRACING
> > > +static __maybe_unused char *configfs_trace_string(struct gadget_info
> > *gi)
> > > +{
> > > + struct usb_configuration *uc;
> > > + struct config_usb_cfg *cfg;
> > > + struct usb_function *f;
> > > + size_t len = sizeof(gi->trace_string) - 1;
> > > + int n = 0;
> > > +
> > > + if (list_empty(&gi->cdev.configs)) {
> > > + strcat(gi->trace_string, "empty");
> > > + return gi->trace_string;
> > > + }
> > > +
> > > + list_for_each_entry(uc, &gi->cdev.configs, list) {
> > > + cfg = container_of(uc, struct config_usb_cfg, c);
> > > +
> > > + n += scnprintf(gi->trace_string + n, len - n,
> > > + "{%d %02x %d ",
> > > + uc->bConfigurationValue,
> > > + uc->bmAttributes,
> > > + uc->MaxPower);
> > > +
> > > + list_for_each_entry(f, &cfg->func_list, list)
> > > + n += scnprintf(gi->trace_string + n,
> > > + len - n, "%s,", f->name);
> > > +
> > > + list_for_each_entry(f, &cfg->c.functions, list)
> > > + n += scnprintf(gi->trace_string + n,
> > > + len - n, "%s,", f->name);
> > > +
> > > + n += scnprintf(gi->trace_string + n, len - n, "};");
> > > + }
> > > +
> > > + return gi->trace_string;
> >
> > I still do not see where you are locking anything to protect the walking
> > of these lists.
> >
> > Where is that now happening?
> With patch#3, my design is all data was protect by gi->lock mutex lock.
> Now trace_string is allocated per instance, it also protected by gi->lock.

That is not obvious at all. Especially as it looked like you did not
protect any list with the patch 3, only attribute values.

Please document this much better at the very least.

Also note that the trace string being per-instance does not change the
locking issues involved here at all.

thanks,

greg k-h