Re: [PATCH 3/3] KVM: Add proper lockdep assertion in I/O bus unregister

[Sean Christopherson]

On Thu, Apr 15, 2021, Jim Mattson wrote:
> On Mon, Apr 12, 2021 at 3:23 PM Sean Christopherson  wrote:
> >
> > Convert a comment above kvm_io_bus_unregister_dev() into an actual
> > lockdep assertion, and opportunistically add curly braces to a multi-line
> > for-loop.
> >
> > Signed-off-by: Sean Christopherson 
> > ---
> >  virt/kvm/kvm_main.c | 6 --
> >  1 file changed, 4 insertions(+), 2 deletions(-)
> >
> > diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
> > index ab1fa6f92c82..ccc2ef1dbdda 100644
> > --- a/virt/kvm/kvm_main.c
> > +++ b/virt/kvm/kvm_main.c
> > @@ -4485,21 +4485,23 @@ int kvm_io_bus_register_dev(struct kvm *kvm, enum 
> > kvm_bus bus_idx, gpa_t addr,
> > return 0;
> >  }
> >
> > -/* Caller must hold slots_lock. */
> >  int kvm_io_bus_unregister_dev(struct kvm *kvm, enum kvm_bus bus_idx,
> >   struct kvm_io_device *dev)
> >  {
> > int i, j;
> > struct kvm_io_bus *new_bus, *bus;
> >
> > +   lockdep_assert_held(>slots_lock);
> > +
> > bus = kvm_get_bus(kvm, bus_idx);
> > if (!bus)
> > return 0;
> >
> > -   for (i = 0; i < bus->dev_count; i++)
> > +   for (i = 0; i < bus->dev_count; i++) {
> > if (bus->range[i].dev == dev) {
> > break;
> > }
> > +   }
> Per coding-style.rst, neither the for loop nor the if-block should have 
> braces.
> 
> "Do not unnecessarily use braces where a single statement will do."

Doh, the if-statement should indeed not use braces.  I think I meant to clean
that up, and then saw something shiny...

But the for-loop... keep reading :-D

Also, use braces when a loop contains more than a single simple statement:

.. code-block:: c

while (condition) {
if (test)
do_something();
}

Re: [PATCH 3/3] KVM: Add proper lockdep assertion in I/O bus unregister

[Jim Mattson]

On Mon, Apr 12, 2021 at 3:23 PM Sean Christopherson  wrote:
>
> Convert a comment above kvm_io_bus_unregister_dev() into an actual
> lockdep assertion, and opportunistically add curly braces to a multi-line
> for-loop.
>
> Signed-off-by: Sean Christopherson 
> ---
>  virt/kvm/kvm_main.c | 6 --
>  1 file changed, 4 insertions(+), 2 deletions(-)
>
> diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
> index ab1fa6f92c82..ccc2ef1dbdda 100644
> --- a/virt/kvm/kvm_main.c
> +++ b/virt/kvm/kvm_main.c
> @@ -4485,21 +4485,23 @@ int kvm_io_bus_register_dev(struct kvm *kvm, enum 
> kvm_bus bus_idx, gpa_t addr,
> return 0;
>  }
>
> -/* Caller must hold slots_lock. */
>  int kvm_io_bus_unregister_dev(struct kvm *kvm, enum kvm_bus bus_idx,
>   struct kvm_io_device *dev)
>  {
> int i, j;
> struct kvm_io_bus *new_bus, *bus;
>
> +   lockdep_assert_held(>slots_lock);
> +
> bus = kvm_get_bus(kvm, bus_idx);
> if (!bus)
> return 0;
>
> -   for (i = 0; i < bus->dev_count; i++)
> +   for (i = 0; i < bus->dev_count; i++) {
> if (bus->range[i].dev == dev) {
> break;
> }
> +   }
Per coding-style.rst, neither the for loop nor the if-block should have braces.

"Do not unnecessarily use braces where a single statement will do."

Stylistic nits aside,

Reviewed-by: Jim Mattson 

[PATCH 3/3] KVM: Add proper lockdep assertion in I/O bus unregister

[Sean Christopherson]

Convert a comment above kvm_io_bus_unregister_dev() into an actual
lockdep assertion, and opportunistically add curly braces to a multi-line
for-loop.

Signed-off-by: Sean Christopherson 
---
 virt/kvm/kvm_main.c | 6 --
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index ab1fa6f92c82..ccc2ef1dbdda 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -4485,21 +4485,23 @@ int kvm_io_bus_register_dev(struct kvm *kvm, enum 
kvm_bus bus_idx, gpa_t addr,
return 0;
 }
 
-/* Caller must hold slots_lock. */
 int kvm_io_bus_unregister_dev(struct kvm *kvm, enum kvm_bus bus_idx,
  struct kvm_io_device *dev)
 {
int i, j;
struct kvm_io_bus *new_bus, *bus;
 
+   lockdep_assert_held(>slots_lock);
+
bus = kvm_get_bus(kvm, bus_idx);
if (!bus)
return 0;
 
-   for (i = 0; i < bus->dev_count; i++)
+   for (i = 0; i < bus->dev_count; i++) {
if (bus->range[i].dev == dev) {
break;
}
+   }
 
if (i == bus->dev_count)
return 0;
-- 
2.31.1.295.g9ea45b61b8-goog