These changes are the raw update to linux-4.4.6-rt14. Kernel sources

are taken from kernel.org, and rt patch from the rt wiki download page.

During the rebasing, the following patch collided:

Force tick interrupt and get rid of softirq magic(I70131fb85).

Collisions have been removed because its logic was found on the
source already.

Change-Id: I7f57a4081d9deaa0d9ccfc41a6c8daccdee3b769
Signed-off-by: José Pekkarinen <jose.pekkarinen@nokia.com>

1 files changed, 37 insertions, 68 deletions

diff --git a/kernel/ipc/msg.c b/kernel/ipc/msg.c
index cedbf5f50..b8c5e7f2b 100644
--- a/kernel/ipc/msg.c
+++ b/kernel/ipc/msg.c
@@ -76,7 +76,7 @@ struct msg_sender {
 
 static inline struct msg_queue *msq_obtain_object(struct ipc_namespace *ns, int id)
 {
-	struct kern_ipc_perm *ipcp = ipc_obtain_object(&msg_ids(ns), id);
+	struct kern_ipc_perm *ipcp = ipc_obtain_object_idr(&msg_ids(ns), id);
 
 	if (IS_ERR(ipcp))
 		return ERR_CAST(ipcp);
@@ -137,13 +137,6 @@ static int newque(struct ipc_namespace *ns, struct ipc_params *params)
 		return retval;
 	}
 
-	/* ipc_addid() locks msq upon success. */
-	id = ipc_addid(&msg_ids(ns), &msq->q_perm, ns->msg_ctlmni);
-	if (id < 0) {
-		ipc_rcu_putref(msq, msg_rcu_free);
-		return id;
-	}
-
 	msq->q_stime = msq->q_rtime = 0;
 	msq->q_ctime = get_seconds();
 	msq->q_cbytes = msq->q_qnum = 0;
@@ -153,6 +146,13 @@ static int newque(struct ipc_namespace *ns, struct ipc_params *params)
 	INIT_LIST_HEAD(&msq->q_receivers);
 	INIT_LIST_HEAD(&msq->q_senders);
 
+	/* ipc_addid() locks msq upon success. */
+	id = ipc_addid(&msg_ids(ns), &msq->q_perm, ns->msg_ctlmni);
+	if (id < 0) {
+		ipc_rcu_putref(msq, msg_rcu_free);
+		return id;
+	}
+
 	ipc_unlock_object(&msq->q_perm);
 	rcu_read_unlock();
 
@@ -183,29 +183,15 @@ static void ss_wakeup(struct list_head *h, int kill)
 	}
 }
 
-static void expunge_all(struct msg_queue *msq, int res)
+static void expunge_all(struct msg_queue *msq, int res,
+			struct wake_q_head *wake_q)
 {
 	struct msg_receiver *msr, *t;
 
 	list_for_each_entry_safe(msr, t, &msq->q_receivers, r_list) {
-		/*
-		 * Make sure that the wakeup doesnt preempt
-		 * this CPU prematurely. (on PREEMPT_RT)
-		 */
-		preempt_disable_rt();
 
-		msr->r_msg = NULL; /* initialize expunge ordering */
-		wake_up_process(msr->r_tsk);
-		/*
-		 * Ensure that the wakeup is visible before setting r_msg as
-		 * the receiving end depends on it: either spinning on a nil,
-		 * or dealing with -EAGAIN cases. See lockless receive part 1
-		 * and 2 in do_msgrcv().
-		 */
-		smp_mb();
+		wake_q_add(wake_q, msr->r_tsk);
 		msr->r_msg = ERR_PTR(res);
-
-		preempt_enable_rt();
 	}
 }
 
@@ -221,11 +207,13 @@ static void freeque(struct ipc_namespace *ns, struct kern_ipc_perm *ipcp)
 {
 	struct msg_msg *msg, *t;
 	struct msg_queue *msq = container_of(ipcp, struct msg_queue, q_perm);
+	WAKE_Q(wake_q);
 
-	expunge_all(msq, -EIDRM);
+	expunge_all(msq, -EIDRM, &wake_q);
 	ss_wakeup(&msq->q_senders, 1);
 	msg_rmid(ns, msq);
 	ipc_unlock_object(&msq->q_perm);
+	wake_up_q(&wake_q);
 	rcu_read_unlock();
 
 	list_for_each_entry_safe(msg, t, &msq->q_messages, m_list) {
@@ -350,6 +338,7 @@ static int msgctl_down(struct ipc_namespace *ns, int msqid, int cmd,
 	struct kern_ipc_perm *ipcp;
 	struct msqid64_ds uninitialized_var(msqid64);
 	struct msg_queue *msq;
+	WAKE_Q(wake_q);
 	int err;
 
 	if (cmd == IPC_SET) {
@@ -397,7 +386,7 @@ static int msgctl_down(struct ipc_namespace *ns, int msqid, int cmd,
 		/* sleeping receivers might be excluded by
 		 * stricter permissions.
 		 */
-		expunge_all(msq, -EAGAIN);
+		expunge_all(msq, -EAGAIN, &wake_q);
 		/* sleeping senders might be able to send
 		 * due to a larger queue size.
 		 */
@@ -410,6 +399,7 @@ static int msgctl_down(struct ipc_namespace *ns, int msqid, int cmd,
 
 out_unlock0:
 	ipc_unlock_object(&msq->q_perm);
+	wake_up_q(&wake_q);
 out_unlock1:
 	rcu_read_unlock();
 out_up:
@@ -574,7 +564,8 @@ static int testmsg(struct msg_msg *msg, long type, int mode)
 	return 0;
 }
 
-static inline int pipelined_send(struct msg_queue *msq, struct msg_msg *msg)
+static inline int pipelined_send(struct msg_queue *msq, struct msg_msg *msg,
+				 struct wake_q_head *wake_q)
 {
 	struct msg_receiver *msr, *t;
 
@@ -582,39 +573,21 @@ static inline int pipelined_send(struct msg_queue *msq, struct msg_msg *msg)
 		if (testmsg(msg, msr->r_msgtype, msr->r_mode) &&
 		    !security_msg_queue_msgrcv(msq, msg, msr->r_tsk,
 					       msr->r_msgtype, msr->r_mode)) {
-			/*
-			 * Make sure that the wakeup doesnt preempt
-			 * this CPU prematurely. (on PREEMPT_RT)
-			 */
-			preempt_disable_rt();
 
 			list_del(&msr->r_list);
 			if (msr->r_maxsize < msg->m_ts) {
-				/* initialize pipelined send ordering */
-				msr->r_msg = NULL;
-				wake_up_process(msr->r_tsk);
-				smp_mb(); /* see barrier comment below */
+				wake_q_add(wake_q, msr->r_tsk);
 				msr->r_msg = ERR_PTR(-E2BIG);
 			} else {
-				msr->r_msg = NULL;
 				msq->q_lrpid = task_pid_vnr(msr->r_tsk);
 				msq->q_rtime = get_seconds();
-				wake_up_process(msr->r_tsk);
-				/*
-				 * Ensure that the wakeup is visible before
-				 * setting r_msg, as the receiving end depends
-				 * on it. See lockless receive part 1 and 2 in
-				 * do_msgrcv().
-				 */
-				smp_mb();
+				wake_q_add(wake_q, msr->r_tsk);
 				msr->r_msg = msg;
-				preempt_enable_rt();
-
 				return 1;
 			}
-			preempt_enable_rt();
 		}
 	}
+
 	return 0;
 }
 
@@ -625,6 +598,7 @@ long do_msgsnd(int msqid, long mtype, void __user *mtext,
 	struct msg_msg *msg;
 	int err;
 	struct ipc_namespace *ns;
+	WAKE_Q(wake_q);
 
 	ns = current->nsproxy->ipc_ns;
 
@@ -710,7 +684,7 @@ long do_msgsnd(int msqid, long mtype, void __user *mtext,
 	msq->q_lspid = task_tgid_vnr(current);
 	msq->q_stime = get_seconds();
 
-	if (!pipelined_send(msq, msg)) {
+	if (!pipelined_send(msq, msg, &wake_q)) {
 		/* no one is waiting for this message, enqueue it */
 		list_add_tail(&msg->m_list, &msq->q_messages);
 		msq->q_cbytes += msgsz;
@@ -724,6 +698,7 @@ long do_msgsnd(int msqid, long mtype, void __user *mtext,
 
 out_unlock0:
 	ipc_unlock_object(&msq->q_perm);
+	wake_up_q(&wake_q);
 out_unlock1:
 	rcu_read_unlock();
 	if (msg != NULL)
@@ -944,31 +919,25 @@ long do_msgrcv(int msqid, void __user *buf, size_t bufsz, long msgtyp, int msgfl
 		rcu_read_lock();
 
 		/* Lockless receive, part 2:
-		 * Wait until pipelined_send or expunge_all are outside of
-		 * wake_up_process(). There is a race with exit(), see
-		 * ipc/mqueue.c for the details.
+		 * The work in pipelined_send() and expunge_all():
+		 * - Set pointer to message
+		 * - Queue the receiver task for later wakeup
+		 * - Wake up the process after the lock is dropped.
+		 *
+		 * Should the process wake up before this wakeup (due to a
+		 * signal) it will either see the message and continue …
 		 */
-		msg = (struct msg_msg *)msr_d.r_msg;
-		while (msg == NULL) {
-			cpu_relax();
-			msg = (struct msg_msg *)msr_d.r_msg;
-		}
 
-		/* Lockless receive, part 3:
-		 * If there is a message or an error then accept it without
-		 * locking.
-		 */
+		msg = (struct msg_msg *)msr_d.r_msg;
 		if (msg != ERR_PTR(-EAGAIN))
 			goto out_unlock1;
 
-		/* Lockless receive, part 3:
-		 * Acquire the queue spinlock.
-		 */
+		 /*
+		  * … or see -EAGAIN, acquire the lock to check the message
+		  * again.
+		  */
 		ipc_lock_object(&msq->q_perm);
 
-		/* Lockless receive, part 4:
-		 * Repeat test after acquiring the spinlock.
-		 */
 		msg = (struct msg_msg *)msr_d.r_msg;
 		if (msg != ERR_PTR(-EAGAIN))
 			goto out_unlock0;