From: Oleg Nesterov 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 Signed-off-by: Andrew Morton --- fs/binfmt_elf.c | 7 +++---- 1 files changed, 3 insertions(+), 4 deletions(-) diff -puN fs/binfmt_elf.c~elf_core_dump-dont-take-tasklist_lock fs/binfmt_elf.c --- a/fs/binfmt_elf.c~elf_core_dump-dont-take-tasklist_lock +++ a/fs/binfmt_elf.c @@ -1479,20 +1479,19 @@ static int elf_core_dump(long signr, str 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; _