Re: [PATCH net-next v13 2/4] ethtool: provide customized dim profile management

[Heng Qi <hengqi@linux.alibaba.com>]

On Mon, 13 May 2024 08:24:12 -0700, Jakub Kicinski <kuba@kernel.org> wrote:
> On Mon, 13 May 2024 22:52:13 +0800 Heng Qi wrote:
> > > > So I think we should declare "CONFIG_PROVE_LOCKING depends on CONFIG_NET".
> > > > How do you think?  
> > > 
> > > Doesn't sound right, `can we instead make building lib/dim/net_dim.c  
> > 
> > Why? IIUC, the reason is that if CONFIG_NET is not set to Y, the net/core
> > directory will not be compiled, so the lockdep_rtnl_is_held symbol is not
> > present.
> 
> Maybe I don't understand what you;re proposing. 
> Show an actual diff please.

Like this:

diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index 291185f54ee4..fbb20d0d08c1 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -1299,7 +1299,7 @@ config LOCK_DEBUGGING_SUPPORT

 config PROVE_LOCKING
        bool "Lock debugging: prove locking correctness"
-       depends on DEBUG_KERNEL && LOCK_DEBUGGING_SUPPORT
+       depends on DEBUG_KERNEL && LOCK_DEBUGGING_SUPPORT && NET
        select LOCKDEP
        select DEBUG_SPINLOCK
        select DEBUG_MUTEXES if !PREEMPT_RT


And there is:

In include/linux/rtnetlink.h:

#ifdef CONFIG_PROVE_LOCKING
extern bool lockdep_rtnl_is_held(void);
#else
static inline bool lockdep_rtnl_is_held(void)
{
        return true;
}
#endif /* #ifdef CONFIG_PROVE_LOCKING */


In net/core/rtnetlink.c:

#ifdef CONFIG_PROVE_LOCKING
bool lockdep_rtnl_is_held(void)
{
        return lockdep_is_held(&rtnl_mutex);
}
EXPORT_SYMBOL(lockdep_rtnl_is_held);
#endif /* #ifdef CONFIG_PROVE_LOCKING */

Thanks.

> 
> > > dependent on CONFIG_NET? Untested but I'm thinking something like:
> > > 
> > > diff --git a/lib/dim/Makefile b/lib/dim/Makefile
> > > index c4cc4026c451..c02c306e2975 100644
> > > --- a/lib/dim/Makefile
> > > +++ b/lib/dim/Makefile
> > > @@ -4,4 +4,8 @@
> > >  
> > >  obj-$(CONFIG_DIMLIB) += dimlib.o
> > >  
> > > -dimlib-objs := dim.o net_dim.o rdma_dim.o
> > > +dimlib-objs := dim.o rdma_dim.o
> > > +
> > > +ifeq ($(CONFIG_NET),y)
> > > +dimlib-objs += net_dim.o
> > > +endif  
> > 
> > 1. This is unlikely to work if the kernel is configured as[1]:
> > 
> > [1] kernel configuration
> > CONFIG_NET=n, CONFIG_ETHTOOL_NETLINK=n, CONFIG_PROVE_LOCKING=y,
> > (CONFIG_FSL_MC_DPIO=y && CONFIG_FSL_MC_BUS=y) select CONFIG_DIMLIB=y.
> > 
> > 
> > Then, because CONFIG_NET is not enabled, so there is no net_dim.o,
> > the following warning appears:
> > 
> > ld.lld: error: undefined symbol: net_dim_get_rx_moderation
> > referenced by dpio-service.c
> > drivers/soc/fsl/dpio/dpio-service.o:(dpaa2_io_dim_work) in archive vmlinux.a
> > 
> > ld.lld: error: undefined symbol: net_dim
> > referenced by dpio-service.c
> > drivers/soc/fsl/dpio/dpio-service.o:(dpaa2_io_update_net_dim) in archive vmlinux.a
> 
> Simple, dpio-service should depend on NET if it wants NET_DIM