From: Thomas Gleixner <tglx@linutronix.de>
To: Al Viro <viro@ZenIV.linux.org.uk>
Cc: LKML <linux-kernel@vger.kernel.org>,
Linus Torvalds <torvalds@osdl.org>, Ingo Molnar <mingo@elte.hu>,
Peter Zijlstra <peterz@infradead.org>,
Nick Piggin <npiggin@kernel.dk>
Subject: Re: [patch 0/5] seqlock consolidation
Date: Thu, 15 Mar 2012 18:55:18 +0100 (CET) [thread overview]
Message-ID: <alpine.LFD.2.02.1203151854110.2466@ionos> (raw)
In-Reply-To: <20120315174305.GD8943@ZenIV.linux.org.uk>
On Thu, 15 Mar 2012, Al Viro wrote:
> On Thu, Mar 15, 2012 at 01:28:03PM +0100, Thomas Gleixner wrote:
>
> > The only way out is to lock d->d_lock which is contended, so the
> > reader side boosts the writer and waits for the lock to be
> > released. Though with the open coded seqlock we have no idea which
> > lock we need to take.
> >
> > Any better ideas ?
>
> So basically you want RT stuff to know that several areas in fs/dcache.c
> (from write_seqcount_begin() to write_seqcount_end()) are protected by
> (already held by that point) ->d_lock of corresponding dentries?
>
> If that's it, I suggest to look for a solution that would express just that...
> Or do you want something on the reader side as well?
The problem is the reader side. If the reader preempts the writer then
the only way to make progress is to take the lock, but therefor I need
to know which lock I should take.
Thanks,
tglx
next prev parent reply other threads:[~2012-03-15 17:55 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-03-15 11:44 Thomas Gleixner
2012-03-15 11:44 ` [patch 1/5] seqlock: Remove unused functions Thomas Gleixner
2012-03-15 16:29 ` Linus Torvalds
2012-03-15 17:39 ` Al Viro
2012-03-15 17:53 ` Thomas Gleixner
2012-03-15 11:44 ` [patch 3/5] seqlock: Provide seq_spin_* functions Thomas Gleixner
2012-03-15 11:44 ` [patch 2/5] seqlock: Use seqcount for seqlock Thomas Gleixner
2012-03-15 11:44 ` [patch 4/5] fs: fs_struct use seqlock Thomas Gleixner
2012-03-15 11:44 ` [patch 5/5] fs: Use seqlock in struct dentry Thomas Gleixner
2012-03-15 12:21 ` [patch 0/5] seqlock consolidation Al Viro
2012-03-15 12:28 ` Thomas Gleixner
2012-03-15 17:43 ` Al Viro
2012-03-15 17:55 ` Thomas Gleixner [this message]
2012-03-15 18:39 ` Al Viro
2012-03-15 19:17 ` Thomas Gleixner
2012-03-15 20:42 ` Al Viro
2012-03-15 22:08 ` Thomas Gleixner
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