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 --- include/linux/init_task.h | 5 +++++ 1 file changed, 5 insertions(+) (limited to 'include/linux/init_task.h') diff --git a/include/linux/init_task.h b/include/linux/init_task.h index 94aefa54a1b5..68ab5f2ab9cd 100644 --- a/include/linux/init_task.h +++ b/include/linux/init_task.h @@ -2,6 +2,7 @@ #define _LINUX__INIT_TASK_H #include +#include #define INIT_FDTABLE \ { \ @@ -11,12 +12,16 @@ .fd = &init_files.fd_array[0], \ .close_on_exec = &init_files.close_on_exec_init, \ .open_fds = &init_files.open_fds_init, \ + .rcu = RCU_HEAD_INIT, \ + .free_files = NULL, \ + .next = NULL, \ } #define INIT_FILES \ { \ .count = ATOMIC_INIT(1), \ .file_lock = SPIN_LOCK_UNLOCKED, \ + .fdt = &init_files.fdtab, \ .fdtab = INIT_FDTABLE, \ .close_on_exec_init = { { 0, } }, \ .open_fds_init = { { 0, } }, \ -- cgit v1.2.3