On 24.08.2013 06:29, Ivan Zhakov wrote: > On Sat, Aug 24, 2013 at 3:48 AM, William A. Rowe Jr. > <wr...@rowe-clan.net> wrote: >> On Fri, 23 Aug 2013 18:39:35 -0500 >> "William A. Rowe Jr." <wr...@rowe-clan.net> wrote: >> >>> On Sat, 24 Aug 2013 00:33:38 +0400 >>> Ivan Zhakov <i...@visualsvn.com> wrote: >>> >>>> Actually Windows supports atomic seek-to-end+write: file should be >>>> opened with FILE_APPEND_DATA access right only [1] or Offset and >>>> OffsetHigh should be 0xFFFFFFFF if overlapped I/O is used [2]. >>>> >>>> I'm reopening this thread because in Subversion we found case where >>>> we need true atomic append across processes/threads. So I'm willing >>>> to create a patch implementing atomic append on Windows. Is right >>>> idea for APR or not? Any concerns will be very helpful. >>>> >>>> [1] >>>> http://msdn.microsoft.com/en-us/library/windows/desktop/aa363778%28v=vs.85%29.aspx >>>> [2] >>>> http://msdn.microsoft.com/en-us/library/windows/desktop/aa365747%28v=vs.85%29.aspx >>> IIRC the difference is that you have writev on unix to atomically >>> write multiple buffers. On Windows we fake writev, so your proposed >>> atomic writes are no longer atomic. > Subversion doesn't use writev for file I/O, so implementing atomic > writes is enough for our case.
Would that mean that writev on Windows uses a mutex while plain write does not? How do you avoid a race between write and writev then? -- Brane
