Re: [PATCH 20/24] task_diag: Only add VMAs for thread_group leader

On 7/14/15 1:47 PM, Oleg Nesterov wrote:

On 07/06, Andrey Vagin wrote:

quoted

From: David Ahern <redacted>

threads of a process share the same VMAs, so when dumping all threads
for all processes only push vma data for group leader.

...

quoted

@@ -492,6 +493,13 @@ static int task_diag_fill(struct task_struct *tsk, struct sk_buff *skb,
  	}

  	if (show_flags & TASK_DIAG_SHOW_VMA) {
+		/* if the request is to dump all threads of all processes
+		 * only show VMAs for group leader.
+		 */
+		if (req->dump_strategy == TASK_DIAG_DUMP_ALL_THREAD &&
+		    !thread_group_leader(tsk))
+			goto done;
+

This doesn't look right, group leader can be a zombie with ->mm == NULL,

Seriously? I'll find some way to track whether VMAs have been dumped for a pid.

quoted

  		if (i >= n)
  			err = fill_vma(tsk, skb, cb, &progress, show_flags);

so this probably needs something like find_lock_task_mm().

ok.

Thanks for the review,
David