Hello,
I posted this to the RTAI mailing list, was wondering if any of you guys could
check this out. I got PREEMPT_RT and RTAI patched to the same kernel but having
trouble building RTAI itself. I was hoping I could maybe get some help here so
we can have LinuxCNC switch between real-time POSIX threads and RTAI on the
same kernel removing the need to reboot. Not really a LinuxCNC question though,
please no ban.
Alec
----- Forwarded Message -----
From: Alec Ari <neotheu...@ymail.com>
To: Rtai <r...@rtai.org>
Sent: Sunday, November 6, 2022 at 07:01:45 PM CST
Subject: Attempt at RTAI and PREEMPT_RT (same kernel)
Hello,
I patched the 5.4 PREEMPT_RT kernel source with IPIPE. The kernel boots and
PREEMPT_RT latency is under 20 microseconds, however upon building RTAI, I get
this:
make[4]: Entering directory '/home/ntu/RTAI/src/ipc/mbx'
CC [M] /home/ntu/RTAI/src/ipc/mbx/mbx.o
In file included from /home/ntu/RTAI/include/rtai_schedcore.h:42,
from /home/ntu/RTAI/src/ipc/mbx/mbx.c:40:
/home/ntu/RTAI/src/ipc/mbx/mbx.c: In function ‘rt_typed_mbx_init’:
./include/linux/spinlock_rt.h:17:16: error: passing argument 1 of
‘rt_typed_sem_init’ from incompatible pointer type
[-Werror=incompatible-pointer-types]
17 | rt_mutex_init(&(slock)->lock); \
| ^~~~~~~~~~~~~~
| |
| struct rt_mutex *
/home/ntu/RTAI/include/rtai_sem.h:244:58: note: in definition of macro
‘rt_mutex_init’
244 | #define rt_mutex_init(mtx) rt_typed_sem_init(mtx, 1, RES_SEM)
| ^~~
/home/ntu/RTAI/src/ipc/mbx/mbx.c:316:2: note: in expansion of macro
‘spin_lock_init’
316 | spin_lock_init(&mbx->lock);
| ^~~~~~~~~~~~~~
/home/ntu/RTAI/include/rtai_sem.h:113:47: note: expected ‘SEM *’ {aka ‘struct
rt_semaphore *’} but argument is of type ‘struct rt_mutex *’
113 | RTAI_SYSCALL_MODE void rt_typed_sem_init(SEM *sem,
| ~~~~~^~~
cc1: some warnings being treated as errors
make[6]: *** [scripts/Makefile.build:262: /home/ntu/RTAI/src/ipc/mbx/mbx.o]
Error 1
make[5]: *** [Makefile:1739: /home/ntu/RTAI/src/ipc/mbx] Error 2
The code in question in mbx.c is this line:
spin_lock_init(&mbx->lock);
from this function:
RTAI_SYSCALL_MODE int rt_typed_mbx_init(MBX *mbx, int size, int type)
{
if (!(mbx->bufadr = rt_malloc(size))) {
return -ENOMEM;
}
rt_typed_sem_init(&(mbx->sndsem), 1, type & 3 ? type : BIN_SEM | type);
rt_typed_sem_init(&(mbx->rcvsem), 1, type & 3 ? type : BIN_SEM | type);
mbx->magic = RT_MBX_MAGIC;
mbx->size = mbx->frbs = size;
mbx->owndby = mbx->waiting_task = NULL;
mbx->fbyte = mbx->lbyte = mbx->avbs = 0;
spin_lock_init(&mbx->lock);
#ifdef CONFIG_RTAI_RT_POLL
mbx->poll_recv.pollq.prev = mbx->poll_recv.pollq.next =
&(mbx->poll_recv.pollq);
mbx->poll_send.pollq.prev = mbx->poll_send.pollq.next =
&(mbx->poll_send.pollq);
mbx->poll_recv.pollq.task = mbx->poll_send.pollq.task = NULL;
spin_lock_init(&(mbx->poll_recv.pollock));
spin_lock_init(&(mbx->poll_send.pollock));
#endif
return 0;
}
This was spin_lock_init() from the vanilla kernel source:
#define spin_lock_init(_lock) \
do { \
spinlock_check(_lock); \
raw_spin_lock_init(&(_lock)->rlock); \
} while (0)
And this is spin_lock_init() from PREEMPT_RT:
#define spin_lock_init(slock) \
do { \
static struct lock_class_key __key; \
\
rt_mutex_init(&(slock)->lock); \
__rt_spin_lock_init(slock, #slock, &__key); \
} while (0)
How do I fix the pointer type?
It would be nice to have RTAI and PREEMPT_RT work together so one kernel can do
it all, no rebooting. I'm also curious if RTAI latency improves.
Alec
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