From: Ingo Molnar Date: Fri, 3 Jul 2009 08:30:12 -0500 Subject: ipc: Make the ipc code -rt aware Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/3.12/patches-3.12.1-rt4.tar.xz RT serializes the code with the (rt)spinlock but keeps preemption enabled. Some parts of the code need to be atomic nevertheless. Protect it with preempt_disable/enable_rt pairts. Signed-off-by: Ingo Molnar Signed-off-by: Thomas Gleixner --- ipc/mqueue.c | 5 +++++ ipc/msg.c | 16 ++++++++++++++++ 2 files changed, 21 insertions(+) --- a/ipc/mqueue.c +++ b/ipc/mqueue.c @@ -923,12 +923,17 @@ static inline void pipelined_send(struct struct msg_msg *message, struct ext_wait_queue *receiver) { + /* + * Keep them in one critical section for PREEMPT_RT: + */ + preempt_disable_rt(); receiver->msg = message; list_del(&receiver->list); receiver->state = STATE_PENDING; wake_up_process(receiver->task); smp_wmb(); receiver->state = STATE_READY; + preempt_enable_rt(); } /* pipelined_receive() - if there is task waiting in sys_mq_timedsend() --- a/ipc/msg.c +++ b/ipc/msg.c @@ -253,10 +253,18 @@ static void expunge_all(struct msg_queue 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; wake_up_process(msr->r_tsk); smp_mb(); msr->r_msg = ERR_PTR(res); + + preempt_enable_rt(); } } @@ -636,6 +644,12 @@ static inline int pipelined_send(struct !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) { msr->r_msg = NULL; @@ -649,9 +663,11 @@ static inline int pipelined_send(struct wake_up_process(msr->r_tsk); smp_mb(); msr->r_msg = msg; + preempt_enable_rt(); return 1; } + preempt_enable_rt(); } } return 0;