From: Al Viro <viro@ZenIV.linux.org.uk>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Eric Dumazet <eric.dumazet@gmail.com>,
Ingo Molnar <mingo@kernel.org>,
Peter Zijlstra <peterz@infradead.org>,
Waiman Long <Waiman.Long@hp.com>,
Benjamin Herrenschmidt <benh@kernel.crashing.org>,
"Chandramouleeswaran, Aswin" <aswin@hp.com>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
linux-fsdevel <linux-fsdevel@vger.kernel.org>
Subject: Re: spinlock contention of files->file_lock
Date: Tue, 1 Oct 2013 04:27:15 +0100 [thread overview]
Message-ID: <20131001032715.GW13318@ZenIV.linux.org.uk> (raw)
In-Reply-To: <CA+55aFz3gJE_DpZufTDNoRZ=vgJS3OwMspR7ZSqzGY_rWMq4gQ@mail.gmail.com>
On Mon, Sep 30, 2013 at 07:02:23PM -0700, Linus Torvalds wrote:
> Shouldn't a cmpxchg() in just the dup2 code solve that?
>
> If the old value was NULL, you'd have to repeat and go back and see if
> the open_fds[] bit had been cleared in the meantime (ie it's NULL not
> because somebody else is busy installing it, but because somebody just
> uninstalled it).
Yechh... Under ->file_lock (in do_dup2()), hopefully? Or you'll get
all kinds of fun with close() thrown into the game, as well...
> But yeah, I do agree that that sounds nasty and a complication I
> hadn't even thought about. dup2() does violate our normal "let's
> pre-allocate the fd slot" rule. Ugh.
Hell knows... Descriptor handling *is* pretty well isolated these
days, so it just might be doable without disrupting the living hell
out of anything else. fs/file.c is pretty much it - everything else
goes through it.
I've enough on my plate at the moment with fs/namespace.c and fs/namei.c,
though, and praying hard fs/inode.c doesn't enter the game. I _know_
that fs/notify will and I'm not enjoying that for a second. BTW, has
eparis resurfaced with any fixes for *notify/umount races? I don't seem
to have anything related in the mailbox, but...
next prev parent reply other threads:[~2013-10-01 3:27 UTC|newest]
Thread overview: 38+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-09-30 19:29 Avoiding the dentry d_lock on final dput(), part deux: transactional memory Linus Torvalds
2013-09-30 19:29 ` Linus Torvalds
2013-09-30 20:01 ` Waiman Long
2013-09-30 20:01 ` Waiman Long
2013-09-30 20:04 ` Linus Torvalds
2013-09-30 20:04 ` Linus Torvalds
2013-10-02 14:56 ` Andi Kleen
2013-10-02 14:56 ` Andi Kleen
2013-09-30 22:52 ` Benjamin Herrenschmidt
2013-09-30 22:52 ` Benjamin Herrenschmidt
2013-10-01 0:36 ` Michael Neuling
2013-10-01 0:36 ` Michael Neuling
2013-10-01 0:56 ` Linus Torvalds
2013-10-01 0:56 ` Linus Torvalds
2013-10-01 2:05 ` Benjamin Herrenschmidt
2013-10-01 2:05 ` Benjamin Herrenschmidt
2013-10-01 3:13 ` Paul E. McKenney
2013-10-01 3:13 ` Paul E. McKenney
2013-10-01 4:52 ` Michael Neuling
2013-10-01 4:52 ` Michael Neuling
2013-10-01 12:16 ` Paul E. McKenney
2013-10-01 12:16 ` Paul E. McKenney
2013-10-01 13:42 ` Paul E. McKenney
2013-10-01 13:42 ` Paul E. McKenney
2013-10-01 1:05 ` spinlock contention of files->file_lock Eric Dumazet
2013-10-01 1:44 ` Linus Torvalds
2013-10-01 2:18 ` Eric Dumazet
2013-10-01 21:41 ` Eric Dumazet
2013-10-01 22:04 ` Al Viro
2013-10-01 22:21 ` Eric Dumazet
2013-10-02 5:13 ` Ingo Molnar
2013-10-02 10:20 ` Al Viro
2013-10-02 10:56 ` Ingo Molnar
2013-10-01 1:53 ` Al Viro
2013-10-01 2:02 ` Linus Torvalds
2013-10-01 3:27 ` Al Viro [this message]
2013-10-01 3:36 ` Eric Dumazet
2013-10-01 5:12 ` Eric Dumazet
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