[PATCH] elf_fdpic_core_dump: don't take tasklist_lock

do_each_thread() is rcu-safe, and all tasks which use this ->mm must sleep
in wait_for_completion(&mm->core_done) at this point, so we can use RCU
locks.

Also, remove unneeded INIT_LIST_HEAD(new) before list_add(new, head).

Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Acked-By: David Howells <dhowells@redhat.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 3 insertions, 4 deletions

diff --git a/fs/binfmt_elf_fdpic.c b/fs/binfmt_elf_fdpic.c
index 2f3365829229..f86d5c9ce5eb 100644
--- a/fs/binfmt_elf_fdpic.c
+++ b/fs/binfmt_elf_fdpic.c
@@ -1597,20 +1597,19 @@ static int elf_fdpic_core_dump(long signr, struct pt_regs *regs,
 
         if (signr) {
                 struct elf_thread_status *tmp;
-                read_lock(&tasklist_lock);
+                rcu_read_lock();
                 do_each_thread(g,p)
                         if (current->mm == p->mm && current != p) {
                                 tmp = kzalloc(sizeof(*tmp), GFP_ATOMIC);
                                 if (!tmp) {
-                                        read_unlock(&tasklist_lock);
+                                        rcu_read_unlock();
                                         goto cleanup;
                                 }
-                                INIT_LIST_HEAD(&tmp->list);
                                 tmp->thread = p;
                                 list_add(&tmp->list, &thread_list);
                         }
                 while_each_thread(g,p);
-                read_unlock(&tasklist_lock);
+                rcu_read_unlock();
                 list_for_each(t, &thread_list) {
                         struct elf_thread_status *tmp;
                         int sz;