diff options
Diffstat (limited to 'winsup/cygwin/flock.cc')
| -rw-r--r-- | winsup/cygwin/flock.cc | 201 |
1 files changed, 200 insertions, 1 deletions
diff --git a/winsup/cygwin/flock.cc b/winsup/cygwin/flock.cc index 1e875113d..f7d19398b 100644 --- a/winsup/cygwin/flock.cc +++ b/winsup/cygwin/flock.cc @@ -1,6 +1,6 @@ /* flock.cc. NT specific implementation of advisory file locking. - Copyright 2003, 2008, 2009, 2010, 2011, 2012 Red Hat, Inc. + Copyright 2003, 2008, 2009, 2010, 2011, 2012, 2013 Red Hat, Inc. This file is part of Cygwin. @@ -915,6 +915,9 @@ static int lf_setlock (lockf_t *, inode_t *, lockf_t **, HANDLE); static void lf_split (lockf_t *, lockf_t *, lockf_t **); static void lf_wakelock (lockf_t *, HANDLE); +/* This is the fcntl advisory lock implementation. For the implementation + of mandatory locks using the Windows mandatory locking functions, see the + fhandler_disk_file::mand_lock method at the end of this file. */ int fhandler_disk_file::lock (int a_op, struct flock *fl) { @@ -1805,3 +1808,199 @@ done: syscall_printf ("%R = lockf(%d, %d, %D)", res, filedes, function, size); return res; } + +/* This is the fcntl lock implementation for mandatory locks using the + Windows mandatory locking functions. For the UNIX-like advisory locking + implementation see the fhandler_disk_file::lock method earlier in this + file. */ +struct lock_parms { + HANDLE h; + PIO_STATUS_BLOCK pio; + PLARGE_INTEGER poff; + PLARGE_INTEGER plen; + BOOL type; + NTSTATUS status; +}; + +static DWORD WINAPI +blocking_lock_thr (LPVOID param) +{ + struct lock_parms *lp = (struct lock_parms *) param; + lp->status = NtLockFile (lp->h, NULL, NULL, NULL, lp->pio, lp->poff, + lp->plen, 0, FALSE, lp->type); + return 0; +} + +int +fhandler_disk_file::mand_lock (int a_op, struct flock *fl) +{ + NTSTATUS status; + IO_STATUS_BLOCK io; + FILE_POSITION_INFORMATION fpi; + FILE_STANDARD_INFORMATION fsi; + off_t startpos; + LARGE_INTEGER offset; + LARGE_INTEGER length; + + /* Calculate where to start from, then adjust this by fl->l_start. */ + switch (fl->l_whence) + { + case SEEK_SET: + startpos = 0; + break; + case SEEK_CUR: + status = NtQueryInformationFile (get_handle (), &io, &fpi, sizeof fpi, + FilePositionInformation); + if (!NT_SUCCESS (status)) + { + __seterrno_from_nt_status (status); + return -1; + } + startpos = fpi.CurrentByteOffset.QuadPart; + break; + case SEEK_END: + status = NtQueryInformationFile (get_handle (), &io, &fsi, sizeof fsi, + FileStandardInformation); + if (!NT_SUCCESS (status)) + { + __seterrno_from_nt_status (status); + return -1; + } + startpos = fsi.EndOfFile.QuadPart; + break; + default: + set_errno (EINVAL); + return -1; + } + /* Adjust start and length until they make sense. */ + offset.QuadPart = startpos + fl->l_start; + if (fl->l_len < 0) + { + offset.QuadPart -= fl->l_len; + length.QuadPart = -fl->l_len; + } + else + length.QuadPart = fl->l_len; + if (offset.QuadPart < 0) + { + length.QuadPart -= -offset.QuadPart; + if (length.QuadPart <= 0) + { + set_errno (EINVAL); + return -1; + } + offset.QuadPart = 0; + } + /* Special case if len == 0. For POSIX this means lock to the end of + the entire file, even when file grows later. */ + if (length.QuadPart == 0) + length.QuadPart = UINT64_MAX; + /* Action! */ + if (fl->l_type == F_UNLCK) + { + status = NtUnlockFile (get_handle (), &io, &offset, &length, 0); + if (status == STATUS_RANGE_NOT_LOCKED) /* Not an error */ + status = STATUS_SUCCESS; + } + else if (a_op == F_SETLKW) + { + /* We open file handles synchronously. To allow asynchronous operation + the file locking functions require a file handle opened in asynchronous + mode. Since Windows locks are per-process/per-file object, we can't + open another handle asynchrously and lock/unlock using that handle: + The original file handle would not have placed the lock and would be + restricted by the lock like any other file handle. + So, what we do here is to start a thread which calls the potentially + blocking NtLockFile call. Then we wait for thread completion in an + interruptible fashion. */ + OBJECT_ATTRIBUTES attr; + HANDLE evt; + struct lock_parms lp = { get_handle (), &io, &offset, &length, + fl->l_type == F_WRLCK, 0 }; + cygthread *thr = NULL; + + InitializeObjectAttributes (&attr, NULL, 0, NULL, NULL); + status = NtCreateEvent (&evt, EVENT_ALL_ACCESS, &attr, + NotificationEvent, FALSE); + if (evt) + thr = new cygthread (blocking_lock_thr, &lp, "blk_lock", evt); + if (!thr) + { + /* Thread creation failed. Fall back to blocking lock call. */ + if (evt) + NtClose (evt); + status = NtLockFile (get_handle (), NULL, NULL, NULL, &io, &offset, + &length, 0, FALSE, fl->l_type == F_WRLCK); + } + else + { + /* F_SETLKW and lock cannot be established. Wait until the lock can + be established, or a signal request arrived. We deliberately + don't handle thread cancel requests here. */ + DWORD wait_res = cygwait (evt, INFINITE, cw_sig | cw_sig_eintr); + NtClose (evt); + switch (wait_res) + { + case WAIT_OBJECT_0: + /* Fetch completion status. */ + status = lp.status; + thr->detach (); + break; + default: + /* Signal arrived. */ + /* Starting with Vista, CancelSynchronousIo works, and we wait + for the thread to exit. lp.status will be either + STATUS_SUCCESS, or STATUS_CANCELLED. We only call + NtUnlockFile in the first case. + Prior to Vista, CancelSynchronousIo doesn't exist, so we + terminated the thread and always call NtUnlockFile since + lp.status was 0 to begin with. */ + if (CancelSynchronousIo (thr->thread_handle ())) + thr->detach (); + else + thr->terminate_thread (); + if (NT_SUCCESS (lp.status)) + NtUnlockFile (get_handle (), &io, &offset, &length, 0); + /* Per SUSv4: If a signal is received while fcntl is waiting, + fcntl shall be interrupted. Upon return from the signal + handler, fcntl shall return -1 with errno set to EINTR, + and the lock operation shall not be done. */ + _my_tls.call_signal_handler (); + set_errno (EINTR); + return -1; + } + } + } + else + { + status = NtLockFile (get_handle (), NULL, NULL, NULL, &io, &offset, + &length, 0, TRUE, fl->l_type == F_WRLCK); + if (a_op == F_GETLK) + { + /* This is non-atomic, but there's no other way on Windows to detect + if another lock is blocking our lock, other than trying to place + the lock, and then having to unlock it again. */ + if (NT_SUCCESS (status)) + { + NtUnlockFile (get_handle (), &io, &offset, &length, 0); + fl->l_type = F_UNLCK; + } + else + { + /* FAKE! FAKE! FAKE! */ + fl->l_type = F_WRLCK; + fl->l_whence = SEEK_SET; + fl->l_start = offset.QuadPart; + fl->l_len = length.QuadPart; + fl->l_pid = (pid_t) -1; + } + status = STATUS_SUCCESS; + } + } + if (!NT_SUCCESS (status)) + { + __seterrno_from_nt_status (status); + return -1; + } + return 0; +} |