At 09:40 AM 3/5/2004, Vladimir Prus wrote:
I have an application which sometimes fails saying that it can't create a
directory, because it already exists. The directory is created by
fs::create_directories("run");
and the application is multi-threaded. It seems there's a race condition:
if (ph.empty() || exists(ph)) return;
// First create branch, by calling ourself recursively create_directories(ph.branch_path()); // Now that parent's path exists, create the directory create_directory(ph);
After one thread checks that 'ph' does not exist, another one creates the
same directory, so call to 'create_directory' fails.
What can be done? Basically, adding a mutex for MT build and adding a warning to docs are the variants. Opinions?
There is already a general race-condition warning in the docs. See www.boost.org/libs/filesystem/doc/index.htm#Race-condition. Even if the filesystem library itself were made thread-safe, the problem could still happen because the state of the external file system may be altered by some other process or other machine. Is there a issue with solving your particular problem by either using your own mutex, or catching and discarding the exception, or moving the create_directory() call to prolog code that is single-threaded? --Beman