linux-kernel - Re: [PATCH 2/6] ipc/mqueue.c: Remove duplicated code

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Date:   Sun, 13 Oct 2019 23:35:11 -0700
From:   Davidlohr Bueso <dave@...olabs.net>
To:     Manfred Spraul <manfred@...orfullife.com>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        Waiman Long <longman@...hat.com>, 1vier1@....de,
        Andrew Morton <akpm@...ux-foundation.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Jonathan Corbet <corbet@....net>
Subject: Re: [PATCH 2/6] ipc/mqueue.c: Remove duplicated code

On Sat, 12 Oct 2019, Manfred Spraul wrote:

>Patch entirely from Davidlohr:
>pipelined_send() and pipelined_receive() are identical, so merge them.
>

Sorry, yeah feel free to add my:

Signed-off-by: Davidlohr Bueso <dbueso@...e.de>

>Signed-off-by: Manfred Spraul <manfred@...orfullife.com>
>Cc: Davidlohr Bueso <dave@...olabs.net>
>---
> ipc/mqueue.c | 31 ++++++++++++++++++-------------
> 1 file changed, 18 insertions(+), 13 deletions(-)
>
>diff --git a/ipc/mqueue.c b/ipc/mqueue.c
>index 3d920ff15c80..be48c0ba92f7 100644
>--- a/ipc/mqueue.c
>+++ b/ipc/mqueue.c
>@@ -918,17 +918,12 @@ SYSCALL_DEFINE1(mq_unlink, const char __user *, u_name)
>  * The same algorithm is used for senders.
>  */
>
>-/* pipelined_send() - send a message directly to the task waiting in
>- * sys_mq_timedreceive() (without inserting message into a queue).
>- */
>-static inline void pipelined_send(struct wake_q_head *wake_q,
>+static inline void __pipelined_op(struct wake_q_head *wake_q,
> 				  struct mqueue_inode_info *info,
>-				  struct msg_msg *message,
>-				  struct ext_wait_queue *receiver)
>+				  struct ext_wait_queue *this)
> {
>-	receiver->msg = message;
>-	list_del(&receiver->list);
>-	wake_q_add(wake_q, receiver->task);
>+	list_del(&this->list);
>+	wake_q_add(wake_q, this->task);
> 	/*
> 	 * Rely on the implicit cmpxchg barrier from wake_q_add such
> 	 * that we can ensure that updating receiver->state is the last
>@@ -937,7 +932,19 @@ static inline void pipelined_send(struct wake_q_head *wake_q,
> 	 * yet, at that point we can later have a use-after-free
> 	 * condition and bogus wakeup.
> 	 */
>-	receiver->state = STATE_READY;
>+        this->state = STATE_READY;
>+}
>+
>+/* pipelined_send() - send a message directly to the task waiting in
>+ * sys_mq_timedreceive() (without inserting message into a queue).
>+ */
>+static inline void pipelined_send(struct wake_q_head *wake_q,
>+				  struct mqueue_inode_info *info,
>+				  struct msg_msg *message,
>+				  struct ext_wait_queue *receiver)
>+{
>+	receiver->msg = message;
>+	__pipelined_op(wake_q, info, receiver);
> }
>
> /* pipelined_receive() - if there is task waiting in sys_mq_timedsend()
>@@ -955,9 +962,7 @@ static inline void pipelined_receive(struct wake_q_head *wake_q,
> 	if (msg_insert(sender->msg, info))
> 		return;
>
>-	list_del(&sender->list);
>-	wake_q_add(wake_q, sender->task);
>-	sender->state = STATE_READY;
>+	__pipelined_op(wake_q, info, sender);
> }
>
> static int do_mq_timedsend(mqd_t mqdes, const char __user *u_msg_ptr,
>-- 
>2.21.0
>