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authorKOBAYASHI Yoshitake <yoshitake.kobayashi@toshiba.co.jp>2011-07-23 02:57:36 (GMT)
committerScott Wood <scottwood@freescale.com>2014-04-10 00:19:04 (GMT)
commitf88491346129d5c5fccf5696415ba4eb4c47c04c (patch)
treedb23e3b9fe5f1c294c5a75cde271d2d4411b2029
parent2451925754ad11895bea6ad37dc13942b04641a8 (diff)
downloadlinux-fsl-qoriq-f88491346129d5c5fccf5696415ba4eb4c47c04c.tar.xz
ipc/mqueue: Add a critical section to avoid a deadlock
(Repost for v3.0-rt1 and changed the distination addreses) I have tested the following patch on v3.0-rt1 with PREEMPT_RT_FULL. In POSIX message queue, if a sender process uses SCHED_FIFO and has a higher priority than a receiver process, the sender will be stuck at ipc/mqueue.c:452 452 while (ewp->state == STATE_PENDING) 453 cpu_relax(); Description of the problem (receiver process) 1. receiver changes sender's state to STATE_PENDING (mqueue.c:846) 2. wake up sender process and "switch to sender" (mqueue.c:847) Note: This context switch only happens in PREEMPT_RT_FULL kernel. (sender process) 3. sender check the own state in above loop (mqueue.c:452-453) *. receiver will never wake up and cannot change sender's state to STATE_READY because sender has higher priority Signed-off-by: Yoshitake Kobayashi <yoshitake.kobayashi@toshiba.co.jp> Cc: viro@zeniv.linux.org.uk Cc: dchinner@redhat.com Cc: npiggin@kernel.dk Cc: hch@lst.de Cc: arnd@arndb.de Link: http://lkml.kernel.org/r/4E2A38A0.1090601@toshiba.co.jp Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
-rw-r--r--ipc/mqueue.c19
1 files changed, 12 insertions, 7 deletions
diff --git a/ipc/mqueue.c b/ipc/mqueue.c
index af0c6bb..2276120 100644
--- a/ipc/mqueue.c
+++ b/ipc/mqueue.c
@@ -947,13 +947,18 @@ static inline void pipelined_receive(struct mqueue_inode_info *info)
wake_up_interruptible(&info->wait_q);
return;
}
- if (msg_insert(sender->msg, info))
- return;
- list_del(&sender->list);
- sender->state = STATE_PENDING;
- wake_up_process(sender->task);
- smp_wmb();
- sender->state = STATE_READY;
+ /*
+ * Keep them in one critical section for PREEMPT_RT:
+ */
+ preempt_disable_rt();
+ if (!msg_insert(sender->msg, info)) {
+ list_del(&sender->list);
+ sender->state = STATE_PENDING;
+ wake_up_process(sender->task);
+ smp_wmb();
+ sender->state = STATE_READY;
+ }
+ preempt_enable_rt();
}
SYSCALL_DEFINE5(mq_timedsend, mqd_t, mqdes, const char __user *, u_msg_ptr,