From: Oleg Nesterov <oleg@redhat.com>
To: Tejun Heo <tj@kernel.org>
Cc: Kent Overstreet <koverstreet@google.com>,
linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org,
linux-aio@kvack.org, akpm@linux-foundation.org,
Zach Brown <zab@redhat.com>, Felipe Balbi <balbi@ti.com>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
Mark Fasheh <mfasheh@suse.com>, Joel Becker <jlbec@evilplan.org>,
Rusty Russell <rusty@rustcorp.com.au>,
Jens Axboe <axboe@kernel.dk>,
Asai Thambi S P <asamymuthupa@micron.com>,
Selvan Mani <smani@micron.com>,
Sam Bradshaw <sbradshaw@micron.com>,
Jeff Moyer <jmoyer@redhat.com>, Al Viro <viro@zeniv.linux.org.uk>,
Benjamin LaHaise <bcrl@kvack.org>,
Christoph Lameter <cl@linux-foundation.org>,
Ingo Molnar <mingo@redhat.com>
Subject: Re: [PATCH 04/21] Generic percpu refcounting
Date: Tue, 14 May 2013 17:28:36 +0200 [thread overview]
Message-ID: <20130514152836.GA21972@redhat.com> (raw)
In-Reply-To: <20130514145932.GA6607@mtj.dyndns.org>
On 05/14, Tejun Heo wrote:
>
> > +int percpu_ref_tryget(struct percpu_ref *ref)
> > +{
> > + int ret = 1;
> > +
> > + preempt_disable();
> > +
> > + if (!percpu_ref_dead(ref))
> > + percpu_ref_get(ref);
> > + else
> > + ret = 0;
> > +
> > + preempt_enable();
> > +
> > + return ret;
> > +}
...
> BTW, why is this
> function necessary? What's the use case?
Yes, I was wondering too.
And please note that this code _looks_ wrong, percpu_ref_get() still
can increment ref->count.
Hmm. Just noticed this comment above percpu_ref_kill()
* The caller must issue a synchronize_rcu()/call_rcu() before calling
* percpu_ref_put() to drop the initial ref.
Really?
Oleg.
next prev parent reply other threads:[~2013-05-14 15:32 UTC|newest]
Thread overview: 52+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-05-14 1:18 AIO refactoring/performance improvements/cancellation Kent Overstreet
2013-05-14 1:18 ` [PATCH 01/21] aio: fix kioctx not being freed after cancellation at exit time Kent Overstreet
2013-05-14 1:18 ` [PATCH 02/21] aio: reqs_active -> reqs_available Kent Overstreet
2013-05-14 1:18 ` [PATCH 03/21] aio: percpu reqs_available Kent Overstreet
2013-05-14 1:18 ` [PATCH 04/21] Generic percpu refcounting Kent Overstreet
2013-05-14 13:51 ` Oleg Nesterov
2013-05-15 8:21 ` Kent Overstreet
2013-05-14 14:59 ` Tejun Heo
2013-05-14 15:28 ` Oleg Nesterov [this message]
2013-05-15 9:00 ` Kent Overstreet
2013-05-15 8:58 ` Kent Overstreet
2013-05-15 17:37 ` Tejun Heo
2013-05-28 23:47 ` Kent Overstreet
2013-05-29 1:11 ` Tejun Heo
2013-05-29 4:59 ` Rusty Russell
2013-05-31 20:12 ` Kent Overstreet
2013-05-14 21:59 ` Tejun Heo
2013-05-14 22:15 ` Tejun Heo
2013-05-15 9:07 ` Kent Overstreet
2013-05-15 17:56 ` Tejun Heo
2013-05-16 0:26 ` Rusty Russell
2013-05-14 1:18 ` [PATCH 05/21] aio: percpu ioctx refcount Kent Overstreet
2013-05-14 1:18 ` [PATCH 06/21] aio: io_cancel() no longer returns the io_event Kent Overstreet
2013-05-14 1:18 ` [PATCH 07/21] aio: Don't use ctx->tail unnecessarily Kent Overstreet
2013-05-14 1:18 ` [PATCH 08/21] aio: Kill aio_rw_vect_retry() Kent Overstreet
2013-05-14 1:18 ` [PATCH 09/21] aio: Kill unneeded kiocb members Kent Overstreet
2013-05-14 1:18 ` [PATCH 10/21] aio: Kill ki_users Kent Overstreet
2013-05-14 1:18 ` [PATCH 11/21] aio: Kill ki_dtor Kent Overstreet
2013-05-14 1:18 ` [PATCH 12/21] aio: convert the ioctx list to radix tree Kent Overstreet
2013-05-14 1:18 ` [PATCH 13/21] block: prep work for batch completion Kent Overstreet
2013-05-14 1:18 ` [PATCH 14/21] block, aio: batch completion for bios/kiocbs Kent Overstreet
2013-05-14 1:18 ` [PATCH 15/21] virtio-blk: convert to batch completion Kent Overstreet
2013-05-14 1:18 ` [PATCH 16/21] mtip32xx: " Kent Overstreet
2013-05-14 1:18 ` [PATCH 17/21] Percpu tag allocator Kent Overstreet
2013-05-14 13:48 ` Oleg Nesterov
2013-05-14 14:24 ` Oleg Nesterov
2013-05-15 9:34 ` Kent Overstreet
2013-05-15 9:25 ` Kent Overstreet
2013-05-15 15:41 ` Oleg Nesterov
2013-05-15 16:10 ` Oleg Nesterov
2013-06-10 23:20 ` Kent Overstreet
2013-06-11 17:42 ` Oleg Nesterov
2013-05-14 15:03 ` Tejun Heo
2013-05-15 20:19 ` Andi Kleen
2013-05-14 1:18 ` [PATCH 18/21] aio: Allow cancellation without a cancel callback, new kiocb lookup Kent Overstreet
2013-05-14 1:18 ` [PATCH 19/21] aio/usb: Update cancellation for new synchonization Kent Overstreet
2013-05-14 1:18 ` [PATCH 20/21] direct-io: Set dio->io_error directly Kent Overstreet
2013-05-14 1:18 ` [PATCH 21/21] block: Bio cancellation Kent Overstreet
2013-05-15 17:52 ` Jens Axboe
2013-05-15 19:29 ` Kent Overstreet
2013-05-15 20:01 ` Jens Axboe
2013-05-31 22:52 ` Kent Overstreet
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