linux-kernel - Re: [PATCH -v3 3/4] lib, Make gen

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Message-ID: <4DA7903B.5030508@intel.com>
Date:	Fri, 15 Apr 2011 08:24:27 +0800
From:	Huang Ying <ying.huang@...el.com>
To:	Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
CC:	Len Brown <lenb@...nel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Andi Kleen <andi@...stfloor.org>,
	"Luck, Tony" <tony.luck@...el.com>,
	"linux-acpi@...r.kernel.org" <linux-acpi@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH -v3 3/4] lib, Make gen_pool memory allocator lockless

On 04/14/2011 05:07 AM, Mathieu Desnoyers wrote:
> * Huang Ying (ying.huang@...el.com) wrote:
> [...]
>> + * rcu_read_lock and rcu_read_unlock is not used int gen_pool_alloc,
>> + * gen_pool_free, gen_pool_avail and gen_pool_size etc, because chunks
>> + * are only added into pool, not deleted from pool unless the pool
>> + * itself is destroyed.  If chunk will be deleted from pool,
>> + * rcu_read_lock and rcu_read_unlock should be uses in these
>> + * functions.
> 
> So how do you protect between pool destruction and adding chunks into
> the pool ?

Because the pool itself will be freed when destruction, we need some
mechanism outside of pool.  For example, if gen_pool_add() is called via
device file IOCTL, we must un-register the device file first, and
destroy the pool after the last reference to device has gone.

Best Regards,
Huang Ying
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