linux-kernel - Re: [PATCH] mm: fix lockdep build in rcu-protected get_mm_exe

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Message-ID: <1427207914.2412.17.camel@stgolabs.net>
Date:	Tue, 24 Mar 2015 07:38:34 -0700
From:	Davidlohr Bueso <dave@...olabs.net>
To:	Oleg Nesterov <oleg@...hat.com>
Cc:	Konstantin Khlebnikov <khlebnikov@...dex-team.ru>,
	linux-mm@...ck.org, Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] mm: fix lockdep build in rcu-protected get_mm_exe_file()

On Mon, 2015-03-23 at 20:10 +0100, Oleg Nesterov wrote:
> "atomic_read(&mm->mm_users) <= 1" looks a bit more "safe". But again,
> I won't insist.

Agreed, it is nicer to do that check, but I have no strong preference
either, perhaps Konstantin or akpm do. Anyway, here's the change that
can be folded in if you guys want to.

Thanks.

8<-------------------------------------------------
diff --git a/kernel/fork.c b/kernel/fork.c
index 98858b5..0c3de2b 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -697,7 +697,7 @@ EXPORT_SYMBOL_GPL(mmput);
 void set_mm_exe_file(struct mm_struct *mm, struct file *new_exe_file)
 {
 	struct file *old_exe_file = rcu_dereference_protected(mm->exe_file,
-			!atomic_read(&mm->mm_users) || current->in_execve);
+			atomic_read(&mm->mm_users) <= 1);
 
 	if (new_exe_file)
 		get_file(new_exe_file);


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