From 48d212a2eecaca2e1875925837ad27b2f43f48a3 Mon Sep 17 00:00:00 2001 From: Linus Torvalds Date: Thu, 7 Jun 2012 17:54:07 -0700 Subject: Revert "mm: correctly synchronize rss-counters at exit/exec" This reverts commit 40af1bbdca47e5c8a2044039bb78ca8fd8b20f94. It's horribly and utterly broken for at least the following reasons: - calling sync_mm_rss() from mmput() is fundamentally wrong, because there's absolutely no reason to believe that the task that does the mmput() always does it on its own VM. Example: fork, ptrace, /proc - you name it. - calling it *after* having done mmdrop() on it is doubly insane, since the mm struct may well be gone now. - testing mm against NULL before you call it is insane too, since a NULL mm there would have caused oopses long before. .. and those are just the three bugs I found before I decided to give up looking for me and revert it asap. I should have caught it before I even took it, but I trusted Andrew too much. Cc: Konstantin Khlebnikov Cc: Markus Trippelsdorf Cc: Hugh Dickins Cc: KAMEZAWA Hiroyuki Cc: Oleg Nesterov Cc: Andrew Morton Signed-off-by: Linus Torvalds --- kernel/fork.c | 8 -------- 1 file changed, 8 deletions(-) (limited to 'kernel/fork.c') diff --git a/kernel/fork.c b/kernel/fork.c index 0560781..ab5211b 100644 --- a/kernel/fork.c +++ b/kernel/fork.c @@ -619,14 +619,6 @@ void mmput(struct mm_struct *mm) module_put(mm->binfmt->module); mmdrop(mm); } - - /* - * Final rss-counter synchronization. After this point there must be - * no pagefaults into this mm from the current context. Otherwise - * mm->rss_stat will be inconsistent. - */ - if (mm) - sync_mm_rss(mm); } EXPORT_SYMBOL_GPL(mmput); -- cgit v1.1