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fix: GetOverlappedResult on ReadDirectoryChangesW hangs on Vista unless hEvent is valid (instead wait with timeout)

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fix: return an error when called before the first watch is registered
(fixes error propagation)

This was SVN commit r7264.
This commit is contained in:
janwas 2010-01-09 23:54:46 +00:00
parent e4be0892f8
commit 8513d57151
1 changed files with 30 additions and 14 deletions
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44
source/lib/sysdep/os/win/wdir_watch.cpp
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@ -74,27 +74,42 @@ private:
class DirWatchRequest
{
NONCOPYABLE(DirWatchRequest);
public:
DirWatchRequest(const fs::wpath& path)
: m_path(path), m_dirHandle(path), m_data(new u8[dataSize], ArrayDeleter())
: m_path(path), m_dirHandle(path), m_data(new u8[dataSize])
{
memset(&m_ovl, 0, sizeof(m_ovl));
// (hEvent is needed for the wait after CancelIo below)
const BOOL manualReset = TRUE;
const BOOL initialState = FALSE;
m_ovl.hEvent = CreateEvent(0, manualReset, initialState, 0);
}
~DirWatchRequest()
{
// m_data's dtor will free the memory after this function returns,
// so the pending IO had better not write into that memory. therefore:
// we need to free m_data here, so the pending IO had better
// not write to that memory in future. therefore:
WARN_IF_FALSE(CancelIo(m_dirHandle));
// however, this is not synchronized with the DPC (?) that apparently
// delivers the data (we have seen m_data being filled regardless).
// delivers the data - m_data is filled anyway.
// we need to ensure that either the IO has happened or that it
// was successfully canceled before freeing m_data, so wait:
{
WinScopedPreserveLastError s;
DWORD dwBytesTransferred = 0; // unused
const BOOL ok = GetOverlappedResult(m_dirHandle, &m_ovl, &dwBytesTransferred, TRUE);
debug_assert(ok || GetLastError() == ERROR_OPERATION_ABORTED);
// (GetOverlappedResult without a valid hEvent hangs on Vista;
// we'll abort after a timeout to be safe.)
const DWORD ret = WaitForSingleObject(m_ovl.hEvent, 1000);
WARN_IF_FALSE(CloseHandle(m_ovl.hEvent));
if(ret == WAIT_OBJECT_0 || GetLastError() == ERROR_OPERATION_ABORTED)
delete[] m_data;
else
{
debug_printf(L"WARNING: canceling IO may have failed; to avoid memory corruption, we won't free the buffer.\n");
DEBUG_WARN_ERR(ERR::TIMED_OUT);
// intentionally leak m_data!
}
}
}
@ -122,8 +137,8 @@ public:
FILE_NOTIFY_CHANGE_CREATION;
// not set: FILE_NOTIFY_CHANGE_ATTRIBUTES, FILE_NOTIFY_CHANGE_LAST_ACCESS, FILE_NOTIFY_CHANGE_SECURITY
DWORD undefined = 0; // (non-NULL pointer avoids BoundsChecker warning)
memset(&m_ovl, 0, sizeof(m_ovl));
const BOOL ok = ReadDirectoryChangesW(m_dirHandle, m_data.get(), dataSize, watchSubtree, filter, &undefined, &m_ovl, 0);
m_ovl.Internal = 0;
const BOOL ok = ReadDirectoryChangesW(m_dirHandle, m_data, dataSize, watchSubtree, filter, &undefined, &m_ovl, 0);
WARN_IF_FALSE(ok);
return INFO::OK;
}
@ -133,7 +148,7 @@ public:
**/
void RetrieveNotifications(DirWatchNotifications& notifications) const
{
const FILE_NOTIFY_INFORMATION* fni = (const FILE_NOTIFY_INFORMATION*)m_data.get();
const FILE_NOTIFY_INFORMATION* fni = (const FILE_NOTIFY_INFORMATION*)m_data;
for(;;)
{
// convert name from BSTR (non-zero-terminated) to std::wstring
@ -185,11 +200,12 @@ private:
// note: each instance needs their own buffer. (we can't share a central
// copy because the watches are independent and may be triggered
// 'simultaneously' before the next poll.)
shared_ptr<u8> m_data;
// NB: lifetime must be managed manually (see dtor)
u8* m_data;
// (ReadDirectoryChangesW's asynchronous mode is triggered by passing
// a valid OVERLAPPED parameter; we don't use its fields because
// notification proceeds via completion ports.)
// a valid OVERLAPPED parameter; notification proceeds via
// completion ports, but we still need hEvent - see above.)
OVERLAPPED m_ovl;
};
@ -304,7 +320,7 @@ public:
LibError Poll(size_t& bytesTransferred, uintptr_t& key, OVERLAPPED*& ovl)
{
if(m_hIOCP == 0)
return INFO::SKIPPED;
return ERR::INVALID_HANDLE; // NOWARN (happens if called before the first Attach)
for(;;) // don't return abort notifications to caller
{
DWORD dwBytesTransferred = 0;