tree 1d58e5e7da61330639ebe62671fb666596d1b00a
parent d5f70c00ad24cd1158d3678b44ff969b4c971d49
author Oleg Nesterov <oleg@tv-sign.ru> 1151306768 -0700
committer Linus Torvalds <torvalds@g5.osdl.org> 1151341107 -0700

[PATCH] coredump: don't take tasklist_lock

This patch removes tasklist_lock from zap_threads().
This is safe wrt:

	do_exit:
		The caller holds mm->mmap_sem. This means that task which
		shares the same ->mm can't pass exit_mm(), so it can't be
		unhashed from init_task.tasks or ->thread_group lists.

	fork:
		None of sub-threads can fork after zap_process(leader). All
		processes which were created before this point should be
		visible to zap_threads() because copy_process() adds the new
		process to the tail of init_task.tasks list, and ->siglock
		lock/unlock provides a memory barrier.

	de_thread:
		It does list_replace_rcu(&leader->tasks, &current->tasks).
		So zap_threads() will see either old or new leader, it does
		not matter. However, it can change p->sighand, so we should
		use lock_task_sighand() in zap_process().

Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>