From ab2af1f5005069321c5d130f09cce577b03f43ef Mon Sep 17 00:00:00 2001 From: Dipankar Sarma Date: Fri, 9 Sep 2005 13:04:13 -0700 Subject: [PATCH] files: files struct with RCU Patch to eliminate struct files_struct.file_lock spinlock on the reader side and use rcu refcounting rcuref_xxx api for the f_count refcounter. The updates to the fdtable are done by allocating a new fdtable structure and setting files->fdt to point to the new structure. The fdtable structure is protected by RCU thereby allowing lock-free lookup. For fd arrays/sets that are vmalloced, we use keventd to free them since RCU callbacks can't sleep. A global list of fdtable to be freed is not scalable, so we use a per-cpu list. If keventd is already handling the current cpu's work, we use a timer to defer queueing of that work. Since the last publication, this patch has been re-written to avoid using explicit memory barriers and use rcu_assign_pointer(), rcu_dereference() premitives instead. This required that the fd information is kept in a separate structure (fdtable) and updated atomically. Signed-off-by: Dipankar Sarma Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- kernel/exit.c | 15 ++++++++------- 1 file changed, 8 insertions(+), 7 deletions(-) (limited to 'kernel/exit.c') diff --git a/kernel/exit.c b/kernel/exit.c index 83beb1e93b18..6d2089a1bce7 100644 --- a/kernel/exit.c +++ b/kernel/exit.c @@ -411,15 +411,16 @@ void fastcall put_files_struct(struct files_struct *files) close_files(files); /* * Free the fd and fdset arrays if we expanded them. + * If the fdtable was embedded, pass files for freeing + * at the end of the RCU grace period. Otherwise, + * you can free files immediately. */ fdt = files_fdtable(files); - if (fdt->fd != &files->fd_array[0]) - free_fd_array(fdt->fd, fdt->max_fds); - if (fdt->max_fdset > __FD_SETSIZE) { - free_fdset(fdt->open_fds, fdt->max_fdset); - free_fdset(fdt->close_on_exec, fdt->max_fdset); - } - kmem_cache_free(files_cachep, files); + if (fdt == &files->fdtab) + fdt->free_files = files; + else + kmem_cache_free(files_cachep, files); + free_fdtable(fdt); } } -- cgit 1.4.1