[PATCH] sys_get_robust_list(): don't take tasklist_lock

use rcu locks for find_task_by_pid().

Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

diff --git a/kernel/futex.c b/kernel/futex.c
index ca8ef11feb6586ce41a825f9c37b791028ed9024..4b6770e9806d0c080ef5f9bd542ddb778ddbcff2 100644 (file)
--- a/kernel/futex.c
+++ b/kernel/futex.c
@@ -1624,7 +1624,7 @@ sys_get_robust_list(int pid, struct robust_list_head __user **head_ptr,
                struct task_struct *p;
 
                ret = -ESRCH;
-               read_lock(&tasklist_lock);
+               rcu_read_lock();
                p = find_task_by_pid(pid);
                if (!p)
                        goto err_unlock;
@@ -1633,7 +1633,7 @@ sys_get_robust_list(int pid, struct robust_list_head __user **head_ptr,
                                !capable(CAP_SYS_PTRACE))
                        goto err_unlock;
                head = p->robust_list;
-               read_unlock(&tasklist_lock);
+               rcu_read_unlock();
        }
 
        if (put_user(sizeof(*head), len_ptr))
@@ -1641,7 +1641,7 @@ sys_get_robust_list(int pid, struct robust_list_head __user **head_ptr,
        return put_user(head, head_ptr);
 
 err_unlock:
-       read_unlock(&tasklist_lock);
+       rcu_read_unlock();
 
        return ret;
 }