The patch titled rework/fix is_single_threaded() has been removed from the -mm tree. Its filename was rework-fix-is_single_threaded.patch This patch was dropped because it was merged into mainline or a subsystem tree The current -mm tree may be found at http://userweb.kernel.org/~akpm/mmotm/ ------------------------------------------------------ Subject: rework/fix is_single_threaded() From: Oleg Nesterov <oleg@xxxxxxxxxx> - 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 <oleg@xxxxxxxxxx> Cc: David Howells <dhowells@xxxxxxxxxx> Cc: James Morris <jmorris@xxxxxxxxx> Cc: Roland McGrath <roland@xxxxxxxxxx> Cc: Stephen Smalley <sds@xxxxxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- lib/is_single_threaded.c | 62 +++++++++++++++++++++---------------- 1 file changed, 36 insertions(+), 26 deletions(-) diff -puN lib/is_single_threaded.c~rework-fix-is_single_threaded lib/is_single_threaded.c --- a/lib/is_single_threaded.c~rework-fix-is_single_threaded +++ a/lib/is_single_threaded.c @@ -12,34 +12,44 @@ #include <linux/sched.h> -/** - * is_single_threaded - Determine if a thread group is single-threaded or not - * @p: A task in the thread group in question - * - * This returns true if the thread group to which a task belongs is single - * threaded, false if it is not. +/* + * Returns true if the task does not share ->mm with another thread/process. */ -bool is_single_threaded(struct task_struct *p) +bool is_single_threaded(struct task_struct *task) { - struct task_struct *g, *t; - struct mm_struct *mm = p->mm; - - if (atomic_read(&p->signal->count) != 1) - goto no; - - if (atomic_read(&p->mm->mm_users) != 1) { - read_lock(&tasklist_lock); - do_each_thread(g, t) { - if (t->mm == mm && t != p) - goto no_unlock; - } while_each_thread(g, t); - read_unlock(&tasklist_lock); + struct mm_struct *mm = task->mm; + struct task_struct *p, *t; + bool ret; + + might_sleep(); + + if (atomic_read(&task->signal->live) != 1) + return false; + + if (atomic_read(&mm->mm_users) == 1) + return true; + + ret = false; + down_write(&mm->mmap_sem); + rcu_read_lock(); + for_each_process(p) { + if (unlikely(p->flags & PF_KTHREAD)) + continue; + if (unlikely(p == task->group_leader)) + continue; + + t = p; + do { + if (unlikely(t->mm == mm)) + goto found; + if (likely(t->mm)) + break; + } while_each_thread(p, t); } + ret = true; +found: + rcu_read_unlock(); + up_write(&mm->mmap_sem); - return true; - -no_unlock: - read_unlock(&tasklist_lock); -no: - return false; + return ret; } _ Patches currently in -mm which might be from oleg@xxxxxxxxxx are linux-next.patch getrusage-fill-ru_maxrss-value.patch getrusage-fill-ru_maxrss-value-update.patch ptrace-__ptrace_detach-do-__wake_up_parent-if-we-reap-the-tracee.patch do_wait-wakeup-optimization-shift-security_task_wait-from-eligible_child-to-wait_consider_task.patch do_wait-wakeup-optimization-change-__wake_up_parent-to-use-filtered-wakeup.patch do_wait-wakeup-optimization-child_wait_callback-check-__wnothread-case.patch do_wait-optimization-do-not-place-sub-threads-on-task_struct-children-list.patch wait_consider_task-kill-parent-argument.patch signals-tracehook_notify_jctl-change.patch utrace-core.patch -- To unsubscribe from this list: send the line "unsubscribe mm-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html