evl/net: skb: fix inconsistent locking of recycling queue

Interrupts on/off mismatch when locking the recycling queue.  At this
chance annotate some routines wrt the legit call context.

[   39.474194] ================================
[   39.474195] WARNING: inconsistent lock state
[   39.474197] 6.1.54+ torvalds#66 Not tainted
[   39.474200] --------------------------------
[   39.474201] inconsistent {HARDIRQ-ON-W} -> {IN-HARDIRQ-W} usage.
[   39.474203] eth0.rx/370 [HC1[0]:SC0[0]:HE0:SE1] takes:
[   39.474207] ffffffff8276b8d8 (recycling_lock){?.+.}-{0:0}, at: free_skb_inband+0x5/0xa0
[   39.474222] {HARDIRQ-ON-W} state was registered at:
[   39.474223]   __lock_acquire+0x363/0x9a0
[   39.474229]   lock_acquire+0xbe/0x2a0
[   39.474233]   free_skb_inband+0x2a/0xa0
[   39.474236]   evl_net_free_skb+0x11/0x90
[   39.474239]   evl_net_do_rx+0x1b7/0x280
[   39.474242]   kthread_trampoline+0x1c7/0x2d0
[   39.474246]   kthread+0xf5/0x120
[   39.474251]   ret_from_fork+0x22/0x30
[   39.474255] irq event stamp: 24
[   39.474256] hardirqs last  enabled at (23): [<ffffffff81b06125>] _raw_spin_unlock_irqrestore+0x65/0x80
[   39.474262] hardirqs last disabled at (24): [<ffffffff81afb971>] __schedule+0x3a1/0x770
[   39.474266] softirqs last  enabled at (0): [<ffffffff810c1ad6>] copy_process+0x796/0x18c0
[   39.474271] softirqs last disabled at (0): [<0000000000000000>] 0x0
[   39.474274]
[   39.474274] other info that might help us debug this:
[   39.474275]  Possible unsafe locking scenario:
[   39.474275]
[   39.474276]        CPU0
[   39.474276]        ----
[   39.474277]   lock(recycling_lock);
[   39.474278]   <Interrupt>
[   39.474279]     lock(recycling_lock);
[   39.474280]
[   39.474280]  *** DEADLOCK ***

Signed-off-by: Philippe Gerum <rpm@xenomai.org>

kernel/evl/net/qdisc/core.c

@@ -15,23 +15,23 @@ static LIST_HEAD(all_net_qdisc);
 
 static DEFINE_MUTEX(qdisc_list_lock);
 
-void evl_net_register_qdisc(struct evl_net_qdisc_ops *ops)
+void evl_net_register_qdisc(struct evl_net_qdisc_ops *ops) /* in-band */
 {
 	mutex_lock(&qdisc_list_lock);
 	list_add(&ops->next, &all_net_qdisc);
 	mutex_unlock(&qdisc_list_lock);
 }
 EXPORT_SYMBOL_GPL(evl_net_register_qdisc);
 
-void evl_net_unregister_qdisc(struct evl_net_qdisc_ops *ops)
+void evl_net_unregister_qdisc(struct evl_net_qdisc_ops *ops) /* in-band */
 {
 	mutex_lock(&qdisc_list_lock);
 	list_del(&ops->next);
 	mutex_unlock(&qdisc_list_lock);
 }
 EXPORT_SYMBOL_GPL(evl_net_unregister_qdisc);
 
-struct evl_net_qdisc *evl_net_alloc_qdisc(struct evl_net_qdisc_ops *ops)
+struct evl_net_qdisc *evl_net_alloc_qdisc(struct evl_net_qdisc_ops *ops) /* in-band */
 {
 	struct evl_net_qdisc *qdisc;
 	int ret;
@@ -53,7 +53,7 @@ struct evl_net_qdisc *evl_net_alloc_qdisc(struct evl_net_qdisc_ops *ops)
 }
 EXPORT_SYMBOL_GPL(evl_net_alloc_qdisc);
 
-void evl_net_free_qdisc(struct evl_net_qdisc *qdisc)
+void evl_net_free_qdisc(struct evl_net_qdisc *qdisc) /* in-band */
 {
 	evl_net_destroy_skb_queue(&qdisc->inband_q);
 	qdisc->oob_ops->destroy(qdisc);
@@ -75,7 +75,7 @@ EXPORT_SYMBOL_GPL(evl_net_free_qdisc);
  *
  *	@dev the device to pass the packet to.
  */
-int evl_net_sched_packet(struct net_device *dev, struct sk_buff *skb) /* oob or in-band */
+int evl_net_sched_packet(struct net_device *dev, struct sk_buff *skb) /* oob/in-band */
 {
 	struct evl_net_qdisc *qdisc = dev->oob_context.dev_state.estate->qdisc;
 

kernel/evl/net/skb.c

@@ -167,10 +167,12 @@ static inline void maybe_kick_recycler(void)
 
 static void free_skb_inband(struct sk_buff *skb)
 {
-	raw_spin_lock(&recycling_lock);
+	unsigned long flags;
+
+	raw_spin_lock_irqsave(&recycling_lock, flags);
 	list_add(&skb->list, &recycling_queue);
 	recycling_count++;
-	raw_spin_unlock(&recycling_lock);
+	raw_spin_unlock_irqrestore(&recycling_lock, flags);
 }
 
 static void free_skb_to_dev(struct sk_buff *skb)
@@ -296,7 +298,7 @@ struct sk_buff *evl_net_clone_skb(struct sk_buff *skb)
  *
  *	@skb the packet to release. Not linked to any upstream queue.
  */
-void evl_net_free_skb(struct sk_buff *skb)
+void evl_net_free_skb(struct sk_buff *skb) /* in-band/oob */
 {
 	EVL_WARN_ON(NET, hard_irqs_disabled());