Re: [PATCH RFC 3/3] vhost, kcov: collect coverage from vhost_worker

On Thu, Oct 17, 2019 at 8:18 PM Greg Kroah-Hartman
[off-list ref] wrote:

On Thu, Oct 17, 2019 at 07:44:15PM +0200, Andrey Konovalov wrote:

quoted

This patch adds kcov_remote_start/kcov_remote_stop annotations to the
vhost_worker function, which is responsible for processing vhost works.
Since vhost_worker is spawned when a vhost device instance is created,
the common kcov handle is used for kcov_remote_start/stop annotations.

Signed-off-by: Andrey Konovalov <redacted>
---
 drivers/vhost/vhost.c | 15 +++++++++++++++
 drivers/vhost/vhost.h |  3 +++
 2 files changed, 18 insertions(+)

diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
index 36ca2cf419bf..71a349f6b352 100644
--- a/drivers/vhost/vhost.c
+++ b/drivers/vhost/vhost.c

@@ -357,7 +357,13 @@ static int vhost_worker(void *data)
              llist_for_each_entry_safe(work, work_next, node, node) {
                      clear_bit(VHOST_WORK_QUEUED, &work->flags);
                      __set_current_state(TASK_RUNNING);
+#ifdef CONFIG_KCOV
+                     kcov_remote_start(dev->kcov_handle);
+#endif

Shouldn't you hide these #ifdefs in a .h file?  This is not a "normal"
kernel coding style at all.

Well, if it's acceptable to add a kcov_handle field into vhost_dev
even when CONFIG_KCOV is not enabled, then we can get rid of those
#ifdefs.

quoted

                      work->fn(work);
+#ifdef CONFIG_KCOV
+                     kcov_remote_stop();
+#endif
                      if (need_resched())
                              schedule();
              }

@@ -546,6 +552,9 @@ long vhost_dev_set_owner(struct vhost_dev *dev)

      /* No owner, become one */
      dev->mm = get_task_mm(current);
+#ifdef CONFIG_KCOV
+     dev->kcov_handle = current->kcov_handle;
+#endif
      worker = kthread_create(vhost_worker, dev, "vhost-%d", current->pid);
      if (IS_ERR(worker)) {
              err = PTR_ERR(worker);

@@ -571,6 +580,9 @@ long vhost_dev_set_owner(struct vhost_dev *dev)
      if (dev->mm)
              mmput(dev->mm);
      dev->mm = NULL;
+#ifdef CONFIG_KCOV
+     dev->kcov_handle = 0;
+#endif
 err_mm:
      return err;
 }

@@ -682,6 +694,9 @@ void vhost_dev_cleanup(struct vhost_dev *dev)
      if (dev->worker) {
              kthread_stop(dev->worker);
              dev->worker = NULL;
+#ifdef CONFIG_KCOV
+             dev->kcov_handle = 0;
+#endif
      }
      if (dev->mm)
              mmput(dev->mm);

diff --git a/drivers/vhost/vhost.h b/drivers/vhost/vhost.h
index e9ed2722b633..010ca1ebcbd5 100644
--- a/drivers/vhost/vhost.h
+++ b/drivers/vhost/vhost.h

@@ -173,6 +173,9 @@ struct vhost_dev {
      int iov_limit;
      int weight;
      int byte_weight;
+#ifdef CONFIG_KCOV
+     u64 kcov_handle;
+#endif

Why is this a #ifdef at all here?

thanks,

greg k-h