[PATCH] elf_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>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

diff --git a/fs/binfmt_elf.c b/fs/binfmt_elf.c
index bb43da5..6eb48e1 100644 (file)
--- a/fs/binfmt_elf.c
+++ b/fs/binfmt_elf.c
@@ -1479,20 +1479,19 @@ static int elf_core_dump(long signr, struct pt_regs *regs, struct file *file)
 
        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;