On 30/08/15 15:19, Alexander Kjeldaas wrote:
The directory is irrelevant. fork() + exec() is not an atomic operation:
* Thread 1 writes its file completely (opens and closes an Fd 1, using O_CLOEXEC) * Thread 2 starts writing its file (Fd 2 open for writing, using O_CLOEXEC) * Thread 1 starts executing "myBinary" by calling *fork()*. Fd 2 is inherited by the child process * Thread 2 finishes writing (closes its Fd 2) * Thread 2 executes "myBinary", which fails with `Text file busy` because an Fd is still open to it in the child of Process 1 * Thread 1 executes "myBinary" (calling exec()). Fd 2 is automatically closed during exec(), but it's too late.
You need the file descriptor to not be inherited by a child process, which is != from O_CLOEXEC.
You are right. This makes solving my original problem impossible, and * writing the file * then renaming it * then executing it seems to be the only way to do it safely. Let us then move the discussion back to whether CLOEXEC by default or not.