lists.openwall.net   lists  /  announce  owl-users  owl-dev  john-users  john-dev  passwdqc-users  yescrypt  popa3d-users  /  oss-security  kernel-hardening  musl  sabotage  tlsify  passwords  /  crypt-dev  xvendor  /  Bugtraq  Full-Disclosure  linux-kernel  linux-netdev  linux-ext4  linux-hardening  linux-cve-announce  PHC 
Open Source and information security mailing list archives
 
Hash Suite: Windows password security audit tool. GUI, reports in PDF.
[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-ID: <54B7323D.9030506@gmail.com>
Date:	Wed, 14 Jan 2015 19:21:33 -0800
From:	John Fastabend <john.fastabend@...il.com>
To:	Thomas Graf <tgraf@...g.ch>
CC:	simon.horman@...ronome.com, sfeldma@...il.com,
	netdev@...r.kernel.org, gerlitz.or@...il.com, jhs@...atatu.com,
	andy@...yhouse.net, davem@...emloft.net
Subject: Re: [net-next PATCH v2 03/12] net: flow: implement flow cache for
 get routines

On 01/14/2015 01:52 PM, Thomas Graf wrote:
> On 01/13/15 at 01:36pm, John Fastabend wrote:
>> I chose rhashtable to get the dynamic resizing. I could use arrays
>> but I don't want to pre-allocate large cache tables when we may
>> never use them.
>>
>> One oddity in the rhashtable implementation is there is no way
>> AFAICS to do delayed free's so we use rcu_sync heavily. This should be
>> fine, get operations shouldn't be a used heavily.
>
> John, can you please clarify a bit, I'm not sure I understand. Are you
> talking about delayed freeing of the table itself or elements?
>
> The Netlink usage would be an example of a user with delayed element
> freeing.
>
> I'm glad to add whatever is required.
>

Took another look at the netlink code looks like this is the correct
pattern where the call_rcu implements the delayed freeing after a grace
period.

	mutex_lock(&my_hash_lock);
	rhashtable_remove(&my_hash, &my_obj->rhash_head);
	mutex_unlock(&my_hash_lock)

	[...]

	call_rcu(&my_obj->rcu, deferred_my_obj_free);

anyways it looks like it is there no problem after all and I don't
recall what I was thinking thanks for bearing with me. I'll convert
this code to avoid the over-use of rcu_sync.

Thanks,
John

-- 
John Fastabend         Intel Corporation
--
To unsubscribe from this list: send the line "unsubscribe netdev" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html

Powered by blists - more mailing lists

Powered by Openwall GNU/*/Linux Powered by OpenVZ