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In cache_io(): Don't keep the cache locked while doing a

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user_{memcpy,memset}(), since that can cause a page fault, which needs
pages and might try to steal some from our cache.


git-svn-id: file:///srv/svn/repos/haiku/haiku/trunk@26700 a95241bf-73f2-0310-859d-f6bbb57e9c96
This commit is contained in:
Ingo Weinhold
2008-07-31 19:23:17 +00:00
parent b627c47932
commit 9a0fc9a874
1 changed files with 34 additions and 21 deletions
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src/system/kernel/cache/file_cache.cpp
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+34 -21
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@@ -626,38 +626,51 @@ cache_io(void *_cacheRef, void *cookie, off_t offset, addr_t buffer,
}
size_t bytesInPage = min_c(size_t(B_PAGE_SIZE - pageOffset), bytesLeft);
addr_t virtualAddress;
TRACE(("lookup page from offset %Ld: %p, size = %lu, pageOffset "
"= %lu\n", offset, page, bytesLeft, pageOffset));
if (page != NULL) {
vm_get_physical_page(page->physical_page_number * B_PAGE_SIZE,
&virtualAddress, PHYSICAL_PAGE_CAN_WAIT);
// Since we don't actually map pages as part of an area, we have
// to manually maintain its usage_count
// to manually maintain their usage_count
page->usage_count = 2;
// and copy the contents of the page already in memory
if (doWrite) {
if (useBuffer) {
user_memcpy((void *)(virtualAddress + pageOffset),
(void *)buffer, bytesInPage);
} else {
user_memset((void *)(virtualAddress + pageOffset),
0, bytesInPage);
if (doWrite || useBuffer) {
// Since the following user_mem{cpy,set}() might cause a page
// fault, which in turn might cause pages to be reserved, we
// need to unlock the cache temporarily to avoid a potential
// deadlock. To make sure that our page doesn't go away, we mark
// it busy for the time.
uint8 oldPageState = page->state;
page->state = PAGE_STATE_BUSY;
locker.Unlock();
addr_t virtualAddress;
vm_get_physical_page(page->physical_page_number * B_PAGE_SIZE,
&virtualAddress, PHYSICAL_PAGE_CAN_WAIT);
// copy the contents of the page already in memory
if (doWrite) {
if (useBuffer) {
user_memcpy((void *)(virtualAddress + pageOffset),
(void *)buffer, bytesInPage);
} else {
user_memset((void *)(virtualAddress + pageOffset),
0, bytesInPage);
}
} else if (useBuffer) {
user_memcpy((void *)buffer,
(void *)(virtualAddress + pageOffset), bytesInPage);
}
// make sure the page is in the modified list
if (page->state != PAGE_STATE_MODIFIED)
vm_page_set_state(page, PAGE_STATE_MODIFIED);
} else if (useBuffer) {
user_memcpy((void *)buffer,
(void *)(virtualAddress + pageOffset), bytesInPage);
}
vm_put_physical_page(virtualAddress);
vm_put_physical_page(virtualAddress);
locker.Lock();
page->state = oldPageState;
if (doWrite && page->state != PAGE_STATE_MODIFIED)
vm_page_set_state(page, PAGE_STATE_MODIFIED);
}
if (bytesLeft <= bytesInPage) {
// we've read the last page, so we're done!