From 8aae2413b38dbbb4da1f816a673748551ca21c34 Mon Sep 17 00:00:00 2001
From: Bart Van Assche <bart.vanassche@sandisk.com>
Date: Fri, 11 Dec 2015 01:39:46 +0000
Subject: [PATCH] ib_srpt: Convert srpt_ch_list_empty() to RCU

This patch avoids that the following warning is reported when
unloading the ib_srpt kernel module:

WARNING: CPU: 9 PID: 33739 at kernel/sched/core.c:7533 __might_sleep+0x82/0x90()
do not call blocking ops when !TASK_RUNNING; state=2 set at [<ffffffff81098b73>] prepare_to_wait_event+0x63/0x110
Call Trace:
 [<ffffffff81251afb>] dump_stack+0x4f/0x74
 [<ffffffff810574cb>] warn_slowpath_common+0x8b/0xd0
 [<ffffffff810575b1>] warn_slowpath_fmt+0x41/0x70
 [<ffffffff810804c2>] __might_sleep+0x82/0x90
 [<ffffffff815186e3>] mutex_lock_nested+0x33/0x380
 [<ffffffffa08eeb7b>] srpt_ch_list_empty+0x2b/0x80 [ib_srpt]
 [<ffffffffa08f000c>] srpt_release_sport+0xcc/0x2a0 [ib_srpt]
 [<ffffffffa08f0215>] srpt_release+0x35/0x80 [ib_srpt]
 [<ffffffffa04d8650>] scst_unregister_target+0x70/0x380 [scst]
 [<ffffffffa08f26c1>] srpt_remove_one+0xb1/0x150 [ib_srpt]
 [<ffffffffa0145a35>] ib_unregister_client+0xe5/0x190 [ib_core]
 [<ffffffffa08f6485>] srpt_cleanup_module+0x21/0x2f [ib_srpt]
 [<ffffffff810dfbfb>] SyS_delete_module+0x17b/0x1c0
 [<ffffffff8151b517>] entry_SYSCALL_64_fastpath+0x12/0x6f


git-svn-id: http://svn.code.sf.net/p/scst/svn/trunk@6726 d57e44dd-8a1f-0410-8b47-8ef2f437770f
---
 srpt/src/ib_srpt.c | 21 ++++++++++++---------
 srpt/src/ib_srpt.h |  2 ++
 2 files changed, 14 insertions(+), 9 deletions(-)

diff --git a/srpt/src/ib_srpt.c b/srpt/src/ib_srpt.c
index 6015f29fa..2d2895335 100644
--- a/srpt/src/ib_srpt.c
+++ b/srpt/src/ib_srpt.c
@@ -2098,7 +2098,7 @@ static void srpt_free_ch(struct kref *kref)
 
 	srpt_destroy_ch_ib(ch);
 
-	kfree(ch);
+	kfree_rcu(ch, rcu);
 }
 
 static void srpt_unreg_ch(struct srpt_rdma_ch *ch)
@@ -2127,7 +2127,7 @@ static void srpt_unreg_ch(struct srpt_rdma_ch *ch)
 	 * after list_del() and before wake_up() has been invoked.
 	 */
 	mutex_lock(&sport->mutex);
-	list_del(&ch->list);
+	list_del_rcu(&ch->list);
 	wake_up(&sport->ch_releaseQ);
 	mutex_unlock(&sport->mutex);
 
@@ -2397,7 +2397,8 @@ static struct srpt_nexus *srpt_get_nexus(struct srpt_port *sport,
 			}
 		}
 		if (!nexus && tmp_nexus) {
-			list_add_tail(&tmp_nexus->entry, &sport->nexus_list);
+			list_add_tail_rcu(&tmp_nexus->entry,
+					  &sport->nexus_list);
 			swap(nexus, tmp_nexus);
 		}
 		mutex_unlock(&sport->mutex);
@@ -2695,7 +2696,7 @@ static int srpt_cm_req_recv(struct srpt_device *const sdev,
 		rsp->rsp_flags = SRP_LOGIN_RSP_MULTICHAN_MAINTAINED;
 	}
 
-	list_add_tail(&ch->list, &nexus->ch_list);
+	list_add_tail_rcu(&ch->list, &nexus->ch_list);
 	ch->thread = thread;
 
 	if (!sport->enabled) {
@@ -3841,11 +3842,11 @@ static bool srpt_ch_list_empty(struct srpt_port *sport)
 	struct srpt_nexus *nexus;
 	bool res = true;
 
-	mutex_lock(&sport->mutex);
-	list_for_each_entry(nexus, &sport->nexus_list, entry)
+	rcu_read_lock();
+	list_for_each_entry_rcu(nexus, &sport->nexus_list, entry)
 		if (!list_empty(&nexus->ch_list))
 			res = false;
-	mutex_unlock(&sport->mutex);
+	rcu_read_unlock();
 
 	return res;
 }
@@ -3885,8 +3886,8 @@ static int srpt_release_sport(struct srpt_port *sport)
 
 	mutex_lock(&sport->mutex);
 	list_for_each_entry_safe(nexus, next_n, &sport->nexus_list, entry) {
-		list_del(&nexus->entry);
-		kfree(nexus);
+		list_del_rcu(&nexus->entry);
+		kfree_rcu(nexus, rcu);
 	}
 	mutex_unlock(&sport->mutex);
 
@@ -4590,6 +4591,8 @@ out:
 
 static void __exit srpt_cleanup_module(void)
 {
+	rcu_barrier();
+
 	if (rdma_cm_id)
 		rdma_destroy_id(rdma_cm_id);
 	ib_unregister_client(&srpt_client);
diff --git a/srpt/src/ib_srpt.h b/srpt/src/ib_srpt.h
index bbe52c011..fdf57791f 100644
--- a/srpt/src/ib_srpt.h
+++ b/srpt/src/ib_srpt.h
@@ -361,6 +361,7 @@ struct srpt_rdma_ch {
 	};
 	struct ib_cq		*cq;
 	struct kref		kref;
+	struct rcu_head		rcu;
 	int			rq_size;
 	int			max_sge;
 	int			max_rsp_size;
@@ -397,6 +398,7 @@ struct srpt_rdma_ch {
 struct srpt_nexus {
 	struct list_head	entry;
 	struct list_head	ch_list;
+	struct rcu_head		rcu;
 	u8			i_port_id[16];
 	u8			t_port_id[16];
 };