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Message-ID: <20180516115906.GF12217@hirez.programming.kicks-ass.net>
Date: Wed, 16 May 2018 13:59:06 +0200
From: Peter Zijlstra <peterz@...radead.org>
To: Oleg Nesterov <oleg@...hat.com>
Cc: Waiman Long <longman@...hat.com>, Ingo Molnar <mingo@...hat.com>,
Thomas Gleixner <tglx@...utronix.de>,
linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org,
Davidlohr Bueso <dave@...olabs.net>,
"Theodore Y. Ts'o" <tytso@....edu>,
Amir Goldstein <amir73il@...il.com>, Jan Kara <jack@...e.cz>,
Matthew Wilcox <willy@...radead.org>
Subject: Re: [PATCH v4 1/2] locking/rwsem: Add a new RWSEM_ANONYMOUSLY_OWNED
flag
On Wed, May 16, 2018 at 12:48:30PM +0200, Oleg Nesterov wrote:
> > +static inline bool is_rwsem_owner_spinnable(struct task_struct *owner)
> > {
> > - return owner && owner != RWSEM_READER_OWNED;
> > + return !((unsigned long)owner & RWSEM_ANONYMOUSLY_OWNED);
> > }
>
> Perhaps you should add __attribute__(aligned) to struct rw_semaphore then...
>
> I don't think it is really needed, but see the comment under struct address_space.
Luckily we just dropped CRIS support, but yeah, who knows if some other
dodgy arch also doesn't properly align things.
>From a quick test, m68k is the only odd one, it seems to align pointers
on 2 bytes.
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