Re: [PATCH] PCI: Mark expected switch fall-throughs

From: Bjorn Helgaas
Date: Wed Mar 20 2019 - 15:24:59 EST


On Wed, Mar 20, 2019 at 01:27:15PM -0500, Gustavo A. R. Silva wrote:
> In preparation to enabling -Wimplicit-fallthrough, mark switch
> cases where we are expecting to fall through.

Does this fix all the remaining cases in drivers/pci? I'd like to fix
them all at once.

What's the best way to watch for new warnings being added? I fiddled
with "make W=2" etc but it didn't seem useful. Does the 0-day robot
warn when -Wimplicit-fallthrough warnings are added?

Bjorn

> This patch fixes the following warnings:
>
> drivers/pci/proc.c: In function âproc_bus_pci_ioctlâ:
> drivers/pci/proc.c:216:6: warning: this statement may fall through [-Wimplicit-fallthrough=]
> if (arch_can_pci_mmap_wc()) {
> ^
> drivers/pci/proc.c:225:2: note: here
> default:
> ^~~~~~~
>
> drivers/pci/xen-pcifront.c: In function âpcifront_backend_changedâ:
> drivers/pci/xen-pcifront.c:1105:6: warning: this statement may fall through [-Wimplicit-fallthrough=]
> if (xdev->state == XenbusStateClosed)
> ^
> drivers/pci/xen-pcifront.c:1108:2: note: here
> case XenbusStateClosing:
> ^~~~
>
> Notice that, in this particular case, the /* fall through */
> comment is placed at the very bottom of the case statement,
> which is what GCC is expecting to find.
>
> Warning level 3 was used: -Wimplicit-fallthrough=3
>
> This patch is part of the ongoing efforts to enable
> -Wimplicit-fallthrough.
>
> Signed-off-by: Gustavo A. R. Silva <gustavo@xxxxxxxxxxxxxx>
> ---
> drivers/pci/proc.c | 1 +
> drivers/pci/xen-pcifront.c | 2 +-
> 2 files changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/pci/proc.c b/drivers/pci/proc.c
> index 6fa1627ce08d..445b51db75b0 100644
> --- a/drivers/pci/proc.c
> +++ b/drivers/pci/proc.c
> @@ -222,6 +222,7 @@ static long proc_bus_pci_ioctl(struct file *file, unsigned int cmd,
> }
> /* If arch decided it can't, fall through... */
> #endif /* HAVE_PCI_MMAP */
> + /* fall through */
> default:
> ret = -EINVAL;
> break;
> diff --git a/drivers/pci/xen-pcifront.c b/drivers/pci/xen-pcifront.c
> index eba6e33147a2..14cf0f41ecf0 100644
> --- a/drivers/pci/xen-pcifront.c
> +++ b/drivers/pci/xen-pcifront.c
> @@ -1104,7 +1104,7 @@ static void __ref pcifront_backend_changed(struct xenbus_device *xdev,
> case XenbusStateClosed:
> if (xdev->state == XenbusStateClosed)
> break;
> - /* Missed the backend's CLOSING state -- fallthrough */
> + /* fall through - Missed the backend's CLOSING state. */
> case XenbusStateClosing:
> dev_warn(&xdev->dev, "backend going away!\n");
> pcifront_try_disconnect(pdev);
> --
> 2.21.0
>