On 06/19/2011 12:14 PM, Gilles Chanteperdrix wrote:
> I am working on this ppd cleanup issue again, I am asking for help to
> find a fix in -head for all cases where the sys_ppd is needed during
> some cleanup.
>
> The problem is that when the ppd cleanup is invoked:
> - we have no guarantee that current is a thread from the Xenomai
> application;
> - if it is, current->mm is NULL.
>
> So, associating the sys_ppd to either current or current->mm does not
> work. What we could do is pass the sys_ppd to all the other ppds cleanup
> handlers, this would fix cases such as freeing mutexes fastlock, but
> that does not help when the sys_ppd is needed during a thread deletion hook.
>
> I would like to find a solution where simply calling xnsys_ppd_get()
> will work, where we do not have an xnsys_ppd_get for each context, such
> as for instance xnsys_ppd_get_by_mm/xnsys_ppd_get_by_task_struct,
> because it would be too error-prone.
>
> Any idea anyone?
The best I could come up with: use a ptd to store the mm currently
being cleaned up, so that xnshadow_ppd_get continues to work, even
in the middle of a cleanup.
diff --git a/ksrc/nucleus/shadow.c b/ksrc/nucleus/shadow.c
index b243600..b542b4f 100644
--- a/ksrc/nucleus/shadow.c
+++ b/ksrc/nucleus/shadow.c
@@ -65,6 +65,8 @@ int nkthrptd;
EXPORT_SYMBOL_GPL(nkthrptd);
int nkerrptd;
EXPORT_SYMBOL_GPL(nkerrptd);
+int nkmmptd;
+EXPORT_SYMBOL_GPL(nkmmptd);
struct xnskin_slot {
struct xnskin_props *props;
@@ -2759,7 +2761,14 @@ static void detach_ppd(xnshadow_ppd_t * ppd)
static inline void do_cleanup_event(struct mm_struct *mm)
{
+ struct mm_struct *old;
+
+ old = (struct mm_struct *)(current->ptd[nkmmptd]);
+ current->ptd[nkmmptd] = mm;
+
ppd_remove_mm(mm, &detach_ppd);
+
+ current->ptd[nkmmptd] = old;
}
RTHAL_DECLARE_CLEANUP_EVENT(cleanup_event);
@@ -2924,8 +2933,14 @@ EXPORT_SYMBOL_GPL(xnshadow_unregister_interface);
*/
xnshadow_ppd_t *xnshadow_ppd_get(unsigned muxid)
{
- if (xnpod_userspace_p())
- return ppd_lookup(muxid, current->mm);
+ if (xnpod_userspace_p()) {
+ struct mm_struct *mm;
+
+ mm = (struct mm_struct *)current->ptd[nkmmptd] ?: current->mm;
+ /* ptd is not null if we are currently cleaning up an mm */
+
+ return ppd_lookup(muxid, mm);
+ }
return NULL;
}
@@ -2960,8 +2975,9 @@ int xnshadow_mount(void)
sema_init(&completion_mutex, 1);
nkthrptd = rthal_alloc_ptdkey();
nkerrptd = rthal_alloc_ptdkey();
+ nkmmptd = rthal_alloc_ptdkey();
- if (nkthrptd < 0 || nkerrptd < 0) {
+ if (nkthrptd < 0 || nkerrptd < 0 || nkmmptd < 0) {
printk(KERN_ERR "Xenomai: cannot allocate PTD slots\n");
return -ENOMEM;
}
diff --git a/ksrc/skins/posix/mutex.c b/ksrc/skins/posix/mutex.c
index 6ce75e5..cc86852 100644
--- a/ksrc/skins/posix/mutex.c
+++ b/ksrc/skins/posix/mutex.c
@@ -219,10 +219,6 @@ void pse51_mutex_destroy_internal(pse51_mutex_t *mutex,
xnlock_put_irqrestore(&nklock, s);
#ifdef CONFIG_XENO_FASTSYNCH
- /* We call xnheap_free even if the mutex is not pshared; when
- this function is called from pse51_mutexq_cleanup, the
- sem_heap is destroyed, or not the one to which the fastlock
- belongs, xnheap will simply return an error. */
xnheap_free(&xnsys_ppd_get(mutex->attr.pshared)->sem_heap,
mutex->synchbase.fastlock);
#endif /* CONFIG_XENO_FASTSYNCH */
--
Gilles.
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