[PATCH] ntdll: Make RtlDeregisterWaitEx(handle, INVALID_HANDLE_VALUE) thread safe.
Stefan Dösinger
stefan at codeweavers.com
Tue Sep 5 10:34:03 CDT 2017
Chromium signals the wait semaphore and calls DeregisterWaitEx with
CompletionHandle = INVALID_HANDLE_VALUE in close succession. Sometimes
the worker thread decides to run the callback, but before it sets
CallbackInProgress RtlDeregisterWaitEx decides that the callback is not
running and returns STATUS_SUCCESS. Chromium then releases resources
that the callback needs to run, resulting in random crashes.
Signed-off-by: Stefan Dösinger <stefan at codeweavers.com>
---
The tests show that we're only supposed to return STATUS_PENDING if the
callback is running. Note that the choice between waiting and returning
STATUS_SUCCESS and not waiting and returning STATUS_PENDING is still
racy, but we'll no longer return STATUS_SUCCESS and run the callback
afterwards.
I tried to extend the tests to show what happens when both events are
available simultanously. The answer is that it is fairly random.
INVALID_HANDLE_VALUE blocks and runs the callback one last time, the
other ways of calling RtlDeregisterWait[Ex] randomly return STATUS_SUCCESS
and do not run the callback, or they return STATUS_PENDING and may or
may not run the callback. However, in no circumstance does the callback
run after STATUS_SUCCESS is returned.
I am not including the tests because of the random outcome and because
it plays with SuspendThread and makes the random failures in follow up
tests worse. I'll send it to wine-devel for reference.
---
dlls/ntdll/threadpool.c | 59 +++++++++++++++++++++++++++----------------------
1 file changed, 32 insertions(+), 27 deletions(-)
diff --git a/dlls/ntdll/threadpool.c b/dlls/ntdll/threadpool.c
index 6063d51d9f..1b0546a781 100644
--- a/dlls/ntdll/threadpool.c
+++ b/dlls/ntdll/threadpool.c
@@ -541,11 +541,13 @@ static DWORD CALLBACK wait_thread_proc(LPVOID Arg)
break;
}
- completion_event = wait_work_item->CompletionEvent;
- if (completion_event) NtSetEvent( completion_event, NULL );
if (interlocked_inc( &wait_work_item->DeleteCount ) == 2 )
+ {
+ completion_event = wait_work_item->CompletionEvent;
delete_wait_work_item( wait_work_item );
+ if (completion_event) NtSetEvent( completion_event, NULL );
+ }
return 0;
}
@@ -633,44 +635,47 @@ NTSTATUS WINAPI RtlRegisterWait(PHANDLE NewWaitObject, HANDLE Object,
NTSTATUS WINAPI RtlDeregisterWaitEx(HANDLE WaitHandle, HANDLE CompletionEvent)
{
struct wait_work_item *wait_work_item = WaitHandle;
- NTSTATUS status = STATUS_SUCCESS;
+ NTSTATUS status;
+ HANDLE LocalEvent = NULL;
+ BOOLEAN CallbackInProgress;
- TRACE( "(%p)\n", WaitHandle );
+ TRACE( "(%p %p)\n", WaitHandle, CompletionEvent );
if (WaitHandle == NULL)
return STATUS_INVALID_HANDLE;
- NtSetEvent( wait_work_item->CancelEvent, NULL );
- if (wait_work_item->CallbackInProgress)
+ CallbackInProgress = wait_work_item->CallbackInProgress;
+ if (CompletionEvent == INVALID_HANDLE_VALUE || !CallbackInProgress)
{
- if (CompletionEvent != NULL)
- {
- if (CompletionEvent == INVALID_HANDLE_VALUE)
- {
- status = NtCreateEvent( &CompletionEvent, EVENT_ALL_ACCESS, NULL, NotificationEvent, FALSE );
- if (status != STATUS_SUCCESS)
- return status;
- interlocked_xchg_ptr( &wait_work_item->CompletionEvent, CompletionEvent );
- if (wait_work_item->CallbackInProgress)
- NtWaitForSingleObject( CompletionEvent, FALSE, NULL );
- NtClose( CompletionEvent );
- }
- else
- {
- interlocked_xchg_ptr( &wait_work_item->CompletionEvent, CompletionEvent );
- if (wait_work_item->CallbackInProgress)
- status = STATUS_PENDING;
- }
- }
- else
- status = STATUS_PENDING;
+ status = NtCreateEvent( &LocalEvent, EVENT_ALL_ACCESS, NULL, NotificationEvent, FALSE );
+ if (status != STATUS_SUCCESS)
+ return status;
+ interlocked_xchg_ptr( &wait_work_item->CompletionEvent, LocalEvent );
+ }
+ else if (CompletionEvent != NULL)
+ {
+ interlocked_xchg_ptr( &wait_work_item->CompletionEvent, CompletionEvent );
}
+ NtSetEvent( wait_work_item->CancelEvent, NULL );
+
if (interlocked_inc( &wait_work_item->DeleteCount ) == 2 )
{
status = STATUS_SUCCESS;
delete_wait_work_item( wait_work_item );
}
+ else if (LocalEvent)
+ {
+ NtWaitForSingleObject( LocalEvent, FALSE, NULL );
+ status = STATUS_SUCCESS;
+ }
+ else
+ {
+ status = STATUS_PENDING;
+ }
+
+ if (LocalEvent)
+ NtClose( LocalEvent );
return status;
}
--
2.13.5
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