On 07/23/2016 03:25 AM, Pranith Kumar Karampuri wrote:
Emmanuel, I procrastinated too long on this :-/, It is July already :-(. I just looked at the man page in Linux and it is a bit confusing, so I am not sure how to go ahead.For readdir_r(), I see: DESCRIPTION This function is deprecated; use readdir(3) instead. The readdir_r() function was invented as a reentrant version of readdir(3). It reads the next directory entry from the directory stream dirp, and returns it in the call‐ er-allocated buffer pointed to by entry. For details of the dirent structure, see readir(3). For readdir(3) I see: ATTRIBUTES For an explanation of the terms used in this section, see attributes(7). ┌──────────┬───────────────┬──────────────────────────┐ │Interface │ Attribute │ Value │ ├──────────┼───────────────┼──────────────────────────┤ │readdir() │ Thread safety │ MT-Unsafe race:dirstream │ └──────────┴───────────────┴──────────────────────────┘ In the current POSIX.1 specification (POSIX.1-2008), readdir() is not required to be thread-safe. However, in modern implementations (including the glibc implementation), concur‐ rent calls to readdir() that specify different directory streams are thread-safe. In cases where multiple threads must read from the same directory stream, using readdir() with external synchronization is still preferable to the use of the deprecated readdir_r(3) function. It is expected that a future version of POSIX.1 will require that readdir() be thread-safe when concurrently employed on different directory streams. So should we do readdir() with external locks for everything instead?
Do you have any concrete examples of problems encountered due to the same directory stream being invoked from multiple threads?
Kaleb's recent patch [1] and the updated man page for readdir_r in linux [2] has some more context.
-Vijay [1] http://review.gluster.org/14838 [2] https://manned.org/readdir_r _______________________________________________ Gluster-devel mailing list Gluster-devel@gluster.org http://www.gluster.org/mailman/listinfo/gluster-devel
