kernel (master) build failure w. !CONFIG_NET_RX_BUSY_POLL

kernel (master) build failure w. !CONFIG_NET_RX_BUSY_POLL

[Mike Galbraith]

Greetings network wizards,

The latest RT explicitly disables CONFIG_NET_RX_BUSY_POLL, thus
uncovering $subject.  Below is what I did about it.

	-Mike

net: Move napi_hash_add/del() inside CONFIG_NET_RX_BUSY_POLL

Since 545cd5e5ec54 ("net: Busy polling should ignore sender CPUs"),
kernel build fails when CONFIG_NET_RX_BUSY_POLL is disabled.  Move
napi_hash_add/del() accordingly.

Banged-upon-by: Mike Galbraith <efault@gmx.de>
---
 include/linux/netdevice.h |    8 ++++++++
 net/core/dev.c            |   12 ++++++++----
 2 files changed, 16 insertions(+), 4 deletions(-)

--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -479,6 +479,8 @@ static inline bool napi_complete(struct
 	return napi_complete_done(n, 0);
 }
 
+#ifdef CONFIG_NET_RX_BUSY_POLL
+
 /**
  *	napi_hash_del - remove a NAPI from global table
  *	@napi: NAPI context
@@ -493,6 +495,12 @@ static inline bool napi_complete(struct
  */
 bool napi_hash_del(struct napi_struct *napi);
 
+#else /* !CONFIG_NET_RX_BUSY_POLL */
+
+static inline bool napi_hash_del(struct napi_struct *napi) { return false; }
+
+#endif /* CONFIG_NET_RX_BUSY_POLL */
+
 /**
  *	napi_disable - prevent NAPI from scheduling
  *	@n: NAPI context
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -184,11 +184,13 @@ static int call_netdevice_notifiers_info
 DEFINE_RWLOCK(dev_base_lock);
 EXPORT_SYMBOL(dev_base_lock);
 
+#ifdef CONFIG_NET_RX_BUSY_POLL
 /* protects napi_hash addition/deletion and napi_gen_id */
 static DEFINE_SPINLOCK(napi_hash_lock);
 
 static unsigned int napi_gen_id = NR_CPUS;
 static DEFINE_READ_MOSTLY_HASHTABLE(napi_hash, 8);
+#endif
 
 static seqcount_t devnet_rename_seq;
 static DEFINE_MUTEX(devnet_rename_mutex);
@@ -5185,6 +5187,8 @@ bool napi_complete_done(struct napi_stru
 }
 EXPORT_SYMBOL(napi_complete_done);
 
+#if defined(CONFIG_NET_RX_BUSY_POLL)
+
 /* must be called under rcu_read_lock(), as we dont take a reference */
 static struct napi_struct *napi_by_id(unsigned int napi_id)
 {
@@ -5198,8 +5202,6 @@ static struct napi_struct *napi_by_id(un
 	return NULL;
 }
 
-#if defined(CONFIG_NET_RX_BUSY_POLL)
-
 #define BUSY_POLL_BUDGET 8
 
 static void busy_poll_stop(struct napi_struct *napi, void *have_poll_lock)
@@ -5300,8 +5302,6 @@ void napi_busy_loop(unsigned int napi_id
 }
 EXPORT_SYMBOL(napi_busy_loop);
 
-#endif /* CONFIG_NET_RX_BUSY_POLL */
-
 static void napi_hash_add(struct napi_struct *napi)
 {
 	if (test_bit(NAPI_STATE_NO_BUSY_POLL, &napi->state) ||
@@ -5341,6 +5341,8 @@ bool napi_hash_del(struct napi_struct *n
 }
 EXPORT_SYMBOL_GPL(napi_hash_del);
 
+#endif /* CONFIG_NET_RX_BUSY_POLL */
+
 static enum hrtimer_restart napi_watchdog(struct hrtimer *timer)
 {
 	struct napi_struct *napi;
@@ -5377,7 +5379,9 @@ void netif_napi_add(struct net_device *d
 	napi->poll_owner = -1;
 #endif
 	set_bit(NAPI_STATE_SCHED, &napi->state);
+#ifdef CONFIG_NET_RX_BUSY_POLL
 	napi_hash_add(napi);
+#endif
 }
 EXPORT_SYMBOL(netif_napi_add);
 

Re: kernel (master) build failure w. !CONFIG_NET_RX_BUSY_POLL

[David Miller]

From: Mike Galbraith <efault@gmx.de>
Date: Wed, 28 Jun 2017 10:01:00 +0200

> Greetings network wizards,
> 
> The latest RT explicitly disables CONFIG_NET_RX_BUSY_POLL, thus
> uncovering $subject.  Below is what I did about it.
> 
> 	-Mike
> 
> net: Move napi_hash_add/del() inside CONFIG_NET_RX_BUSY_POLL
> 
> Since 545cd5e5ec54 ("net: Busy polling should ignore sender CPUs"),
> kernel build fails when CONFIG_NET_RX_BUSY_POLL is disabled.  Move
> napi_hash_add/del() accordingly.
> 
> Banged-upon-by: Mike Galbraith <efault@gmx.de>

First, this is in no way a standard signoff or ack tag.

Second, you must provide the complete set of build failure details
so that anyone just reading your posting can understand and fully
review your patch without having to go anywhere else for the
pertinent information.

And, lastly, I can't see how anything like this could be necessary
with the way the code is currently structures in the 'net' tree.  This
is really why you need to make a full report, with build failure
messages, as well as an explanation of what your change does, and why
it does it that way.

Thanks.

Re: kernel (master) build failure w. !CONFIG_NET_RX_BUSY_POLL

[Mike Galbraith]

On Thu, 2017-06-29 at 15:35 -0400, David Miller wrote:
> From: Mike Galbraith <efault@gmx.de>
> Date: Wed, 28 Jun 2017 10:01:00 +0200
> 
> > Greetings network wizards,
> > 
> > The latest RT explicitly disables CONFIG_NET_RX_BUSY_POLL, thus
> > uncovering $subject.  Below is what I did about it.
> > 
> >       -Mike
> > 
> > net: Move napi_hash_add/del() inside CONFIG_NET_RX_BUSY_POLL
> > 
> > Since 545cd5e5ec54 ("net: Busy polling should ignore sender CPUs"),
> > kernel build fails when CONFIG_NET_RX_BUSY_POLL is disabled.  Move
> > napi_hash_add/del() accordingly.
> > 
> > Banged-upon-by: Mike Galbraith <efault@gmx.de>
> 
> First, this is in no way a standard signoff or ack tag.

It's not intended to be, it's intended to stress that this in not a
submission, it's a local fix for a problem that network folks will
likely fix up differently... but who knows, showing what I did about it
after taking a look could perhaps save a wee bit of labor, so...

Hohum, so much for good intentions.  I though I was clearly showing
that separation of the polling business was not as complete as other
changes led me to believe it is intended to be.

> Second, you must provide the complete set of build failure details
> so that anyone just reading your posting can understand and fully
> review your patch without having to go anywhere else for the
> pertinent information.

Here's the naked failure instead.

  CC      net/core/dev.o
net/core/dev.c: In function ‘napi_hash_add’:
net/core/dev.c:5315:43: error: ‘MIN_NAPI_ID’ undeclared (first use in this function)
   if (unlikely(++napi_gen_id < MIN_NAPI_ID))
                                           ^
net/core/dev.c:5315:43: note: each undeclared identifier is reported only once for each function it appears in
scripts/Makefile.build:302: recipe for target 'net/core/dev.o' failed
make[1]: *** [net/core/dev.o] Error 1
Makefile:1663: recipe for target 'net/core/dev.o' failed
make: *** [net/core/dev.o] Error 2

	-Mike