From: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
To: Dan Carpenter <dan.carpenter@oracle.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
devel@driverdev.osuosl.org, Minchan Kim <minchan@kernel.org>,
Jerome Marchand <jmarchan@redhat.com>,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH 1/2] staging: zram: minimize `slot_free_lock' usage (v2)
Date: Mon, 9 Sep 2013 18:09:42 +0300 [thread overview]
Message-ID: <20130909150942.GC2221@swordfish.minsk.epam.com> (raw)
In-Reply-To: <20130909145229.GB19256@mwanda>
On (09/09/13 17:52), Dan Carpenter wrote:
> On Mon, Sep 09, 2013 at 05:42:59PM +0300, Sergey Senozhatsky wrote:
> > > 3) Explain why it is safe to test zram->slot_free_rq when we are not
> > > holding the lock. I think it is unsafe. I don't want to even think
> > > about it without the numbers.
> >
> > atomic pointer test, which is either NULL or !NULL.
> >
>
> That's not how concurency works. Atomic types are complicated than
> that. Anyway, the zram maintainers don't need me to explain that to
> them so I'll let them take over from here.
>
yes, I understand that. but can't we check slot_free_rq pointer
(32 or 64 bit read) w/o locking to just decide if we must:
-- call handle_pending_slot_free()
-- take the slot_free_lock
-- check slot_free_rq again (this time under the slot_free_lock) and perform
slot_free_rq operations while it is !NULL.
-ss
> regards,
> dan carpenter
>
prev parent reply other threads:[~2013-09-09 15:11 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-09-06 15:12 Sergey Senozhatsky
2013-09-09 12:33 ` Dan Carpenter
2013-09-09 12:49 ` Sergey Senozhatsky
2013-09-09 13:21 ` Dan Carpenter
2013-09-09 13:46 ` Jerome Marchand
2013-09-09 16:10 ` Jerome Marchand
2013-09-10 14:34 ` Sergey Senozhatsky
2013-09-10 14:58 ` Dan Carpenter
2013-09-10 15:15 ` Greg Kroah-Hartman
2013-09-10 23:12 ` [PATCH 1/2] staging: zram: fix handle_pending_slot_free() and zram_reset_device() race Sergey Senozhatsky
2013-09-12 22:12 ` Greg KH
2013-09-13 9:17 ` Sergey Senozhatsky
2013-09-16 0:02 ` Minchan Kim
2013-09-17 17:24 ` Sergey Senozhatsky
2013-09-23 4:24 ` Minchan Kim
2013-09-23 8:42 ` Sergey Senozhatsky
2013-09-10 23:19 ` [PATCH 2/2] staging: zram: remove init_done from zram struct (v3) Sergey Senozhatsky
2013-09-10 23:27 ` [PATCH 1/2] staging: zram: minimize `slot_free_lock' usage (v2) Sergey Senozhatsky
2013-09-09 14:42 ` Sergey Senozhatsky
2013-09-09 14:52 ` Dan Carpenter
2013-09-09 15:09 ` Sergey Senozhatsky [this message]
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