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* Fixed a deadlock (and resolved TODO): we need to make all pages unbusy again

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before releasing our cache reference. Otherwise removing a vnode (triggered
  by releasing the cache in our thread) could need pages we still own.
* Put the caches and pages into a union to save stack space; they are not
  needed at the same time.


git-svn-id: file:///srv/svn/repos/haiku/haiku/trunk@23580 a95241bf-73f2-0310-859d-f6bbb57e9c96
This commit is contained in:
Axel Dörfler 2008-01-17 08:21:48 +00:00
parent 9e7511601a
commit 53f7979709
1 changed files with 23 additions and 14 deletions
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37
src/system/kernel/vm/vm_page.cpp
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@ -461,6 +461,7 @@ dump_page(int argc, char **argv)
kprintf("state: %s\n", page_state_to_string(page->state));
kprintf("wired_count: %d\n", page->wired_count);
kprintf("usage_count: %d\n", page->usage_count);
kprintf("busy_writing: %d\n", page->busy_writing);
#ifdef DEBUG_PAGE_QUEUE
kprintf("queue: %p\n", page->queue);
#endif
@ -924,7 +925,10 @@ page_writer(void* /*unused*/)
const uint32 kNumPages = 32;
ConditionVariable<vm_page> busyConditions[kNumPages];
vm_page *pages[kNumPages];
union {
vm_page *pages[kNumPages];
vm_cache *caches[kNumPages];
} u;
uint32 numPages = 0;
// TODO: once the I/O scheduler is there, we should write
@ -972,7 +976,7 @@ page_writer(void* /*unused*/)
//dprintf("write page %p, cache %p (%ld)\n", page, page->cache, page->cache->ref_count);
vm_clear_map_flags(page, PAGE_MODIFIED);
vm_cache_acquire_ref(cache);
pages[numPages++] = page;
u.pages[numPages++] = page;
}
if (numPages == 0)
@ -983,42 +987,47 @@ page_writer(void* /*unused*/)
// TODO: put this as requests into the I/O scheduler
status_t writeStatus[kNumPages];
for (uint32 i = 0; i < numPages; i++) {
writeStatus[i] = write_page(pages[i], false);
writeStatus[i] = write_page(u.pages[i], false);
}
// mark pages depending on whether they could be written or not
for (uint32 i = 0; i < numPages; i++) {
vm_cache *cache = pages[i]->cache;
vm_cache *cache = u.pages[i]->cache;
mutex_lock(&cache->lock);
if (writeStatus[i] == B_OK) {
// put it into the active queue
InterruptsSpinLocker locker(sPageLock);
move_page_to_active_or_inactive_queue(pages[i], true);
pages[i]->busy_writing = false;
move_page_to_active_or_inactive_queue(u.pages[i], true);
u.pages[i]->busy_writing = false;
} else {
// We don't have to put the PAGE_MODIFIED bit back, as it's
// still in the modified pages list.
{
InterruptsSpinLocker locker(sPageLock);
pages[i]->state = PAGE_STATE_MODIFIED;
enqueue_page(&sModifiedPageQueue, pages[i]);
u.pages[i]->state = PAGE_STATE_MODIFIED;
enqueue_page(&sModifiedPageQueue, u.pages[i]);
}
if (!pages[i]->busy_writing) {
if (!u.pages[i]->busy_writing) {
// someone has cleared the busy_writing flag which tells
// us our page has gone invalid
vm_cache_remove_page(cache, pages[i]);
vm_cache_remove_page(cache, u.pages[i]);
} else
pages[i]->busy_writing = false;
u.pages[i]->busy_writing = false;
}
busyConditions[i].Unpublish();
u.caches[i] = cache;
mutex_unlock(&cache->lock);
// TODO: we need to release the cache references after all
// pages are made unbusy again - otherwise releasing a vnode
// could deadlock.
}
for (uint32 i = 0; i < numPages; i++) {
vm_cache *cache = u.caches[i];
// We release the cache references after all pages were made
// unbusy again - otherwise releasing a vnode could deadlock.
if (cache->store->ops->release_ref != NULL)
cache->store->ops->release_ref(cache->store);
vm_cache_release_ref(cache);