[PATCH v2] kcov, usb: hide in_serving_softirq checks in __usb_hcd_giveback_urb

[PATCH v2] kcov, usb: hide in_serving_softirq checks in __usb_hcd_giveback_urb

[Andrey Konovalov]

Done opencode in_serving_softirq() checks in __usb_hcd_giveback_urb() to
avoid cluttering the code, hide them in kcov helpers instead.

Fixes: aee9ddb1d371 ("kcov, usb: only collect coverage from __usb_hcd_giveback_urb in softirq")
Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
---

Changes v1->v2:
- Fix a typo in the commit description and in a comment in the patch.

---
 drivers/usb/core/hcd.c |  8 +++-----
 include/linux/kcov.h   | 21 +++++++++++++++++++++
 2 files changed, 24 insertions(+), 5 deletions(-)

diff --git a/drivers/usb/core/hcd.c b/drivers/usb/core/hcd.c
index 60886a7464c3..ad5a0f405a75 100644
--- a/drivers/usb/core/hcd.c
+++ b/drivers/usb/core/hcd.c
@@ -1649,14 +1649,12 @@ static void __usb_hcd_giveback_urb(struct urb *urb)
 	urb->status = status;
 	/*
 	 * This function can be called in task context inside another remote
-	 * coverage collection section, but KCOV doesn't support that kind of
+	 * coverage collection section, but kcov doesn't support that kind of
 	 * recursion yet. Only collect coverage in softirq context for now.
 	 */
-	if (in_serving_softirq())
-		kcov_remote_start_usb((u64)urb->dev->bus->busnum);
+	kcov_remote_start_usb_softirq((u64)urb->dev->bus->busnum);
 	urb->complete(urb);
-	if (in_serving_softirq())
-		kcov_remote_stop();
+	kcov_remote_stop_softirq();
 
 	usb_anchor_resume_wakeups(anchor);
 	atomic_dec(&urb->use_count);
diff --git a/include/linux/kcov.h b/include/linux/kcov.h
index a10e84707d82..18306ef8ad5a 100644
--- a/include/linux/kcov.h
+++ b/include/linux/kcov.h
@@ -52,6 +52,25 @@ static inline void kcov_remote_start_usb(u64 id)
 	kcov_remote_start(kcov_remote_handle(KCOV_SUBSYSTEM_USB, id));
 }
 
+/*
+ * The softirq flavor of kcov_remote_*() functions is introduced as a temporary
+ * workaround for kcov's lack of nested remote coverage sections support in
+ * task context. Adding suport for nested sections is tracked in:
+ * https://bugzilla.kernel.org/show_bug.cgi?id=210337
+ */
+
+static inline void kcov_remote_start_usb_softirq(u64 id)
+{
+	if (in_serving_softirq())
+		kcov_remote_start_usb(id);
+}
+
+static inline void kcov_remote_stop_softirq(void)
+{
+	if (in_serving_softirq())
+		kcov_remote_stop();
+}
+
 #else
 
 static inline void kcov_task_init(struct task_struct *t) {}
@@ -66,6 +85,8 @@ static inline u64 kcov_common_handle(void)
 }
 static inline void kcov_remote_start_common(u64 id) {}
 static inline void kcov_remote_start_usb(u64 id) {}
+static inline void kcov_remote_start_usb_softirq(u64 id) {}
+static inline void kcov_remote_stop_softirq(void) {}
 
 #endif /* CONFIG_KCOV */
 #endif /* _LINUX_KCOV_H */
-- 
2.29.2.729.g45daf8777d-goog

Re: [PATCH v2] kcov, usb: hide in_serving_softirq checks in __usb_hcd_giveback_urb

[Greg Kroah-Hartman]

On Thu, Jan 07, 2021 at 05:01:44PM +0100, Andrey Konovalov wrote:
> Done opencode in_serving_softirq() checks in __usb_hcd_giveback_urb() to
> avoid cluttering the code, hide them in kcov helpers instead.
> 
> Fixes: aee9ddb1d371 ("kcov, usb: only collect coverage from __usb_hcd_giveback_urb in softirq")
> Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
> ---
> 
> Changes v1->v2:
> - Fix a typo in the commit description and in a comment in the patch.

I can't drop the previous one, so can you just make a follow-on patch
please?

thanks,

greg k-h