From: Oleg Nesterov Date: Wed, 29 Mar 2006 00:10:59 +0000 (-0800) Subject: [PATCH] simplify exec from init's subthread X-Git-Url: https://git.stricted.de/?a=commitdiff_plain;h=1434261c07bcebd5ef8b8a18f919fdee533b84e0;p=GitHub%2Fmt8127%2Fandroid_kernel_alcatel_ttab.git [PATCH] simplify exec from init's subthread I think it is enough to take tasklist_lock for reading while changing child_reaper: Reparenting needs write_lock(tasklist_lock) Only one thread in a thread group can do exec() sighand->siglock garantees that get_signal_to_deliver() will not see a stale value of child_reaper. This means that we can change child_reaper earlier, without calling zap_other_threads() twice. "child_reaper = current" is a NOOP when init does exec from main thread, we don't care. Signed-off-by: Oleg Nesterov Acked-by: "Eric W. Biederman" Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- diff --git a/fs/exec.c b/fs/exec.c index d0ecea0781f7..dd194923c52c 100644 --- a/fs/exec.c +++ b/fs/exec.c @@ -616,6 +616,15 @@ static int de_thread(struct task_struct *tsk) kmem_cache_free(sighand_cachep, newsighand); return -EAGAIN; } + + /* + * child_reaper ignores SIGKILL, change it now. + * Reparenting needs write_lock on tasklist_lock, + * so it is safe to do it under read_lock. + */ + if (unlikely(current->group_leader == child_reaper)) + child_reaper = current; + zap_other_threads(current); read_unlock(&tasklist_lock); @@ -660,23 +669,12 @@ static int de_thread(struct task_struct *tsk) struct dentry *proc_dentry1, *proc_dentry2; unsigned long ptrace; - leader = current->group_leader; - /* - * If our leader is the child_reaper become - * the child_reaper and resend SIGKILL signal. - */ - if (unlikely(leader == child_reaper)) { - write_lock(&tasklist_lock); - child_reaper = current; - zap_other_threads(current); - write_unlock(&tasklist_lock); - } - /* * Wait for the thread group leader to be a zombie. * It should already be zombie at this point, most * of the time. */ + leader = current->group_leader; while (leader->exit_state != EXIT_ZOMBIE) yield();