svn commit: r236935 - head/sys/kern

[David Xu]

On 2012/6/12 6:05, Pawel Jakub Dawidek wrote:
> Author: pjd
> Date: Mon Jun 11 22:05:26 2012
> New Revision: 236935
> URL: http://svn.freebsd.org/changeset/base/236935
>
> Log:
>    fdgrowtable() no longer drops the filedesc lock so it is enough to
>    retry finding free file descriptor only once after fdgrowtable().
>
>    Spotted by:	pluknet
>    MFC after:	1 month
>
> Modified:
>    head/sys/kern/kern_descrip.c
>
> Modified: head/sys/kern/kern_descrip.c
> ==============================================================================
> --- head/sys/kern/kern_descrip.c	Mon Jun 11 21:56:37 2012	(r236934)
> +++ head/sys/kern/kern_descrip.c	Mon Jun 11 22:05:26 2012	(r236935)
> @@ -1478,29 +1478,33 @@ fdalloc(struct thread *td, int minfd, in
>   	/*
>   	 * Search the bitmap for a free descriptor.  If none is found, try
>   	 * to grow the file table.  Keep at it until we either get a file
> -	 * descriptor or run into process or system limits; fdgrowtable()
> -	 * may drop the filedesc lock, so we're in a race.
> +	 * descriptor or run into process or system limits.
>   	 */
> -	for (;;) {
> -		fd = fd_first_free(fdp, minfd, fdp->fd_nfiles);
> -		if (fd>= maxfd)
> -			return (EMFILE);
> -		if (fd<  fdp->fd_nfiles)
> -			break;
> +	fd = fd_first_free(fdp, minfd, fdp->fd_nfiles);
> +	if (fd>= maxfd)
> +		return (EMFILE);
> +	if (fd>= fdp->fd_nfiles) {
>   #ifdef RACCT
>   		PROC_LOCK(p);
> -		error = racct_set(p, RACCT_NOFILE, min(fdp->fd_nfiles * 2, maxfd));
> +		error = racct_set(p, RACCT_NOFILE,
> +		    min(fdp->fd_nfiles * 2, maxfd));
>   		PROC_UNLOCK(p);
>   		if (error != 0)
>   			return (EMFILE);
>   #endif
>   		fdgrowtable(fdp, min(fdp->fd_nfiles * 2, maxfd));
> +		/* Retry... */
> +		fd = fd_first_free(fdp, minfd, fdp->fd_nfiles);
> +		if (fd>= maxfd)
> +			return (EMFILE);
>   	}
>
>   	/*
>   	 * Perform some sanity checks, then mark the file descriptor as
>   	 * used and return it to the caller.
>   	 */
> +	KASSERT((unsigned int)fd<  min(maxfd, fdp->fd_nfiles),
> +	    ("invalid descriptor %d", fd));
>   	KASSERT(!fdisused(fdp, fd),
>   	    ("fd_first_free() returned non-free descriptor"));
>   	KASSERT(fdp->fd_ofiles[fd] == NULL, ("file descriptor isn't free"));
>
My machine crashed with this change.
http://people.freebsd.org/~davidxu/fdcrash.jpg


Regards,