* Re: [Xenomai-core] [PATCH] Fix to RTDM open problems
2006-01-27 10:29 [Xenomai-core] [PATCH] Fix to RTDM open problems Anders Blomdell
@ 2006-01-27 12:03 ` Jan Kiszka
2006-01-27 12:48 ` Luotao Fu
0 siblings, 1 reply; 3+ messages in thread
From: Jan Kiszka @ 2006-01-27 12:03 UTC (permalink / raw)
To: Anders Blomdell; +Cc: xenomai
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Anders Blomdell wrote:
> When RTDM is exposed to code like this:
>
> device1 = rt_dev_open("some_device", O_RDWR);
> device2 = rt_dev_open("some_device", O_RDWR);
>
> I get a SEGFAULT, which I attribute to a missing assignment to
> context_ptr in the case when the device is already busy, the lack of
> this assignment leads to a segfault in cleanup_instance.
>
>
> --- xenomai-2.1-rc2/ksrc/skins/rtdm/core.c~ 2006-01-07
> 18:08:34.000000000 +0100
> +++ xenomai-2.1-rc2/ksrc/skins/rtdm/core.c 2006-01-27
> 11:14:43.000000000 +0100
> @@ -136,6 +136,8 @@
>
> if (context->device) {
> xnlock_put_irqrestore(&rt_dev_lock, s);
> +
> + *context_ptr = NULL;
> return -EBUSY;
> }
> context->device = device;
>
Yep, correct. Don't know, I must have smoked something while trying to
fix this bug some weeks ago. Thanks for reporting and also providing a
patch.
I just gave it another try, also re-organising the involved function
create_instance() slightly. Please checkout latest SVN or try the
following patch and let me know if this works now, really.
Thanks again,
Jan
Index: core.c
===================================================================
--- core.c (revision 475)
+++ core.c (working copy)
@@ -116,13 +116,13 @@
spl_t s;
+ *context_ptr = NULL;
+
xnlock_get_irqsave(&rt_fildes_lock, s);
*fildes_ptr = fildes = free_fildes;
- if (!fildes) {
+ if (unlikely(!fildes)) {
xnlock_put_irqrestore(&rt_fildes_lock, s);
-
- *context_ptr = NULL;
return -ENFILE;
}
free_fildes = fildes->next;
@@ -134,15 +134,13 @@
if (context) {
xnlock_get_irqsave(&rt_dev_lock, s);
- if (context->device) {
+ if (unlikely(context->device)) {
xnlock_put_irqrestore(&rt_dev_lock, s);
return -EBUSY;
}
context->device = device;
xnlock_put_irqrestore(&rt_dev_lock, s);
-
- *context_ptr = context;
} else {
if (nrt_mem)
context = kmalloc(sizeof(struct rtdm_dev_context) +
@@ -150,13 +148,14 @@
else
context = xnmalloc(sizeof(struct rtdm_dev_context) +
device->context_size);
- *context_ptr = context;
- if (!context)
+ if (unlikely(!context))
return -ENOMEM;
context->device = device;
}
+ *context_ptr = context;
+
context->fd = get_fd(fildes);
context->ops = &device->ops;
atomic_set(&context->close_lock_count, 0);
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