On Wednesday 23 March 2016 14:38:05 David Miller wrote:
> From: Andrew Lunn <and...@lunn.ch>
> Date: Wed, 23 Mar 2016 17:51:11 +0100
>
> > On Wed, Mar 23, 2016 at 05:37:38PM +0100, Arnd Bergmann wrote:
> >> dev_dbg_ratelimited() is a macro that ignores its arguments when DEBUG is
> >> not set, which can lead to unused variable warnings:
> >>
> >> ethernet/mellanox/mlxsw/pci.c: In function 'mlxsw_pci_cqe_sdq_handle':
> >> ethernet/mellanox/mlxsw/pci.c:646:18: warning: unused variable 'pdev'
> >> [-Wunused-variable]
> >> ethernet/mellanox/mlxsw/pci.c: In function 'mlxsw_pci_cqe_rdq_handle':
> >> ethernet/mellanox/mlxsw/pci.c:671:18: warning: unused variable 'pdev'
> >> [-Wunused-variable]
> >>
> >> This changes the mlxsw driver to remove the local variables we get
> >> warnings for and instead pass the device directly into the API.
> >
> > Hi Arnd
> >
> > Would it not be better to fix the macro?
> >
> > I think the issue is that dev_dbg_ratelimited calls no_printk(),
> > without making use of dev. So how about:
> >
> > #define dev_dbg_ratelimited(dev, fmt, ...) \
> > ({ \
> > if (0) \
> > dev_printk(KERN_DEBUG, dev, fmt, ##__VA_ARGS__); \
> > })
> >
> > This follows the pattern for other macros for when DEBUG is not defined.
>
> Yeah, this is probably a better way to fix this problem.
Makes sense. I was thrown off by how a related patch recently
modified the no_printk() definition in Fixes: fe22cd9b7c98 ("printk:
help pr_debug and pr_devel to optimize out arguments") around the
same time I ran into the problem in the mlxsw driver.
I'll test build the patch below for a while and submit that if it doesn't
cause any other problems.
diff --git a/include/linux/device.h b/include/linux/device.h
index 002c59728dbe..07f74c246cac 100644
--- a/include/linux/device.h
+++ b/include/linux/device.h
@@ -1293,8 +1293,11 @@ do {
\
dev_printk(KERN_DEBUG, dev, fmt, ##__VA_ARGS__); \
} while (0)
#else
-#define dev_dbg_ratelimited(dev, fmt, ...) \
- no_printk(KERN_DEBUG pr_fmt(fmt), ##__VA_ARGS__)
+#define dev_dbg_ratelimited(dev, fmt, ...) \
+do { \
+ if (0) \
+ dev_printk(KERN_DEBUG, dev, fmt, ##__VA_ARGS__); \
+} while (0)
#endif
#ifdef VERBOSE_DEBUG
Thanks,
Arnd
