ipc: drop lockless pipelined wakeups patch

2 files changed, 0 insertions, 230 deletions

diff --git a/patches/ipc-msg-Implement-lockless-pipelined-wakeups.patch b/patches/ipc-msg-Implement-lockless-pipelined-wakeups.patch
deleted file mode 100644
index dcab30eacdb09..0000000000000
--- a/patches/ipc-msg-Implement-lockless-pipelined-wakeups.patch
+++ /dev/null
@@ -1,227 +0,0 @@
-From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
-Date: Fri, 30 Oct 2015 11:59:07 +0100
-Subject: ipc/msg: Implement lockless pipelined wakeups
-
-This patch moves the wakeup_process() invocation so it is not done under
-the perm->lock by making use of a lockless wake_q. With this change, the
-waiter is woken up once the message has been assigned and it does not
-need to loop on SMP if the message points to NULL. In the signal case we
-still need to check the pointer under the lock to verify the state.
-
-This change should also avoid the introduction of preempt_disable() in
--RT which avoids a busy-loop which pools for the NULL -> !NULL
-change if the waiter has a higher priority compared to the waker.
-
-Cc: Davidlohr Bueso <dave@stgolabs.net>
-Cc: Manfred Spraul <manfred@colorfullife.com>
-Cc: Andrew Morton <akpm@linux-foundation.org>
-Cc: George Spelvin <linux@horizon.com>
-Cc: Thomas Gleixner <tglx@linutronix.de>
-Cc: Peter Zijlstra <peterz@infradead.org>
-Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
----
-
- ipc/msg.c |  101 +++++++++++++++++---------------------------------------------
- 1 file changed, 28 insertions(+), 73 deletions(-)
-
---- a/ipc/msg.c
-+++ b/ipc/msg.c
-@@ -183,20 +183,14 @@ static void ss_wakeup(struct list_head *
- 	}
- }
- 
--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) {
--		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_wmb(); /* barrier (B) */
-+
-+		wake_q_add(wake_q, msr->r_tsk);
- 		msr->r_msg = ERR_PTR(res);
- 	}
- }
-@@ -213,11 +207,13 @@ static void freeque(struct ipc_namespace
- {
- 	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) {
-@@ -342,6 +338,7 @@ static int msgctl_down(struct ipc_namesp
- 	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) {
-@@ -389,7 +386,7 @@ static int msgctl_down(struct ipc_namesp
- 		/* 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.
- 		 */
-@@ -402,6 +399,7 @@ static int msgctl_down(struct ipc_namesp
- 
- out_unlock0:
- 	ipc_unlock_object(&msq->q_perm);
-+	wake_up_q(&wake_q);
- out_unlock1:
- 	rcu_read_unlock();
- out_up:
-@@ -566,7 +564,8 @@ static int testmsg(struct msg_msg *msg,
- 	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;
- 
-@@ -577,27 +576,13 @@ static inline int pipelined_send(struct
- 
- 			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);
--				/* barrier (B) see barrier comment below */
--				smp_wmb();
-+				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 can otherwise
--				 * exit - once r_msg is set, the receiver can
--				 * continue. See lockless receive part 1 and 2
--				 * in do_msgrcv(). Barrier (B).
--				 */
--				smp_wmb();
-+				wake_q_add(wake_q, msr->r_tsk);
- 				msr->r_msg = msg;
--
- 				return 1;
- 			}
- 		}
-@@ -613,6 +598,7 @@ long do_msgsnd(int msqid, long mtype, vo
- 	struct msg_msg *msg;
- 	int err;
- 	struct ipc_namespace *ns;
-+	WAKE_Q(wake_q);
- 
- 	ns = current->nsproxy->ipc_ns;
- 
-@@ -698,7 +684,7 @@ long do_msgsnd(int msqid, long mtype, vo
- 	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;
-@@ -712,6 +698,7 @@ long do_msgsnd(int msqid, long mtype, vo
- 
- out_unlock0:
- 	ipc_unlock_object(&msq->q_perm);
-+	wake_up_q(&wake_q);
- out_unlock1:
- 	rcu_read_unlock();
- 	if (msg != NULL)
-@@ -932,57 +919,25 @@ long do_msgrcv(int msqid, void __user *b
- 		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 correct serialization
--		 * ensures that a receiver cannot continue without the wakeup
--		 * being visibible _before_ setting r_msg:
-+		 * 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.
- 		 *
--		 * CPU 0                             CPU 1
--		 * <loop receiver>
--		 *   smp_rmb(); (A) <-- pair -.      <waker thread>
--		 *   <load ->r_msg>           |        msr->r_msg = NULL;
--		 *                            |        wake_up_process();
--		 * <continue>                 `------> smp_wmb(); (B)
--		 *                                     msr->r_msg = msg;
--		 *
--		 * Where (A) orders the message value read and where (B) orders
--		 * the write to the r_msg -- done in both pipelined_send and
--		 * expunge_all.
-+		 * Should the process wake up before this wakeup (due to a
-+		 * signal) it will either see the message and continue …
- 		 */
--		for (;;) {
--			/*
--			 * Pairs with writer barrier in pipelined_send
--			 * or expunge_all.
--			 */
--			smp_rmb(); /* barrier (A) */
--			msg = (struct msg_msg *)msr_d.r_msg;
--			if (msg)
--				break;
- 
--			/*
--			 * The cpu_relax() call is a compiler barrier
--			 * which forces everything in this loop to be
--			 * re-loaded.
--			 */
--			cpu_relax();
--		}
--
--		/* 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;
diff --git a/patches/series b/patches/series
index cb912ab4d0cf1..4fa4020f1050e 100644
--- a/patches/series
+++ b/patches/series
@@ -256,9 +256,6 @@ radix-tree-rt-aware.patch
 # PANIC
 panic-disable-random-on-rt.patch
 
-# IPC
-ipc-msg-Implement-lockless-pipelined-wakeups.patch
-
 # RELAY
 relay-fix-timer-madness.patch