[PATCH] files: lock-free fd look-up

With the use of RCU in files structure, the look-up of files using fds can now
be lock-free.  The lookup is protected by rcu_read_lock()/rcu_read_unlock().
This patch changes the readers to use lock-free lookup.

Signed-off-by: Maneesh Soni <maneesh@in.ibm.com>
Signed-off-by: Ravikiran Thirumalai <kiran_th@gmail.com>
Signed-off-by: Dipankar Sarma <dipankar@in.ibm.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 2 insertions, 2 deletions

diff --git a/drivers/char/tty_io.c b/drivers/char/tty_io.c
index 0bfc7af68917..e5953f3433f3 100644
--- a/drivers/char/tty_io.c
+++ b/drivers/char/tty_io.c
@@ -2480,7 +2480,7 @@ static void __do_SAK(void *arg)
                 }
                 task_lock(p);
                 if (p->files) {
-                        spin_lock(&p->files->file_lock);
+                        rcu_read_lock();
                         fdt = files_fdtable(p->files);
                         for (i=0; i < fdt->max_fds; i++) {
                                 filp = fcheck_files(p->files, i);
@@ -2495,7 +2495,7 @@ static void __do_SAK(void *arg)
                                         break;
                                 }
                         }
-                        spin_unlock(&p->files->file_lock);
+                        rcu_read_unlock();
                 }
                 task_unlock(p);
         } while_each_task_pid(session, PIDTYPE_SID, p);