From: Oleg Nesterov Date: Thu, 16 Jul 2009 23:09:36 +0000 (+1000) Subject: kernel: fix is_single_threaded X-Git-Tag: v2.6.32-rc1~737^2^2~43 X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=d2e3ee9b29f5de5b01e611b04e6fb29760589b01;p=pandora-kernel.git kernel: fix is_single_threaded - Fix the comment, is_single_threaded(p) actually means that nobody shares ->mm with p. I think this helper should be renamed, and it should not have arguments. With or without this patch it must not be used unless p == current, otherwise we can't safely use p->signal or p->mm. - "if (atomic_read(&p->signal->count) != 1)" is not right when we have a zombie group leader, use signal->live instead. - Add PF_KTHREAD check to skip kernel threads which may borrow p->mm, otherwise we can return the wrong "false". - Use for_each_process() instead of do_each_thread(), all threads must use the same ->mm. - Use down_write(mm->mmap_sem) + rcu_read_lock() instead of tasklist_lock to iterate over the process list. If there is another CLONE_VM process it can't pass exit_mm() which takes the same mm->mmap_sem. We can miss a freshly forked CLONE_VM task, but this doesn't matter because we must see its parent and return false. Signed-off-by: Oleg Nesterov Cc: David Howells Cc: James Morris Cc: Roland McGrath Cc: Stephen Smalley Signed-off-by: Andrew Morton Signed-off-by: James Morris --- Reading git-diff-tree failed