Johannes Sixt <j6t@xxxxxxxx> writes: > As this buglet looks like a recurring theme, and a proper fix is > preferable over repeated work-arounds. To me it looks like we need > some sort of locking on Windows. Unless your friends at Microsoft have > an ace in their sleeves that lets us have atomic O_APPEND the POSIX > way... Just to put the severity of the issue in context, we use O_APPEND in a few codepaths, and the trace thing for debugging is the only thing that could have multiple writers. Other users of O_APPEND are: * refs/files-backend.c uses it so that a reflog entry can be appended at the end, but because update to each ref is protected from racing at a lot higher layer with a lock, no two people would try to append to the same reflog file, so atomicity of O_APPEND does not matter here. * sequencer.c wants to use it when moving one insn from the todo list to the 'done' list when it finishes one operation. If you are running two sequences in a single repository, intermixed 'done' list would be the least of your problem, so presumably we are fine here. It may make sense to allow GIT_TRACE to have a placeholder (e.g. "/tmp/traceout.$$") to help debuggers arrange to give different processes their own trace output file, which perhaps may be a simpler and less impactful to the performance solution than having to make locks at an application layer.
