lkml.org 
[lkml]   [2014]   [Jun]   [30]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH 0/3] static keys: fix test/set races
Hi Steve,

I took a closer look at this, and I'm thinking now that its simpler to
just take the &inode->i_mutex in sched_feat_write(), surrounding the
test/set jump_label call. It should be about 3 lines :)

I started re-working this with the patches in this series and it just
seemed like a lot of code for only 1 current use-case. (The udp case
doesn't appear to disable the branch and thus is not racy.)

So I've swung back to what Ingo originally said - I can test/post the
suggested 3-line patch, unless there are other thoughts...

Thanks,

-Jason

On 06/23/2014 10:28 PM, Steven Rostedt wrote:
>
> Cleaning out my INBOX I found this patch series. It seems to have been
> forgotten about. It ended up with Ingo and Peter agreeing with the way
> things should be done and I thought Jason was going to send an update.
> But that seems to never have happened.
>
> Does this patch series still look legit? Should we pursue it?
>
> -- Steve
>
> On Fri, 28 Jun 2013 22:30:28 +0000 (GMT)
> jbaron@akamai.com wrote:
>
>> Hi,
>>
>> As pointed out by Andi Kleen, some static key users can be racy because they
>> check the value of the key->enabled, and then subsequently update the branch
>> direction. A number of call sites have 'higher' level locking that avoids this
>> race, but the usage in the scheduler features does not. See:
>> http://lkml.indiana.edu/hypermail/linux/kernel/1304.2/01655.html
>>
>> Thus, introduce a new API that does the check and set under the
>> 'jump_label_mutex'. This should also allow to simplify call sites a bit.
>>
>> Users of static keys should use either the inc/dec or the set_true/set_false
>> API.
>>
>> Thanks,
>>
>> -Jason
>>
>>
>> Jason Baron (3):
>> static_keys: Add a static_key_slow_set_true()/false() interface
>> sched: fix static keys race in sched_feat
>> udp: make use of static_key_slow_set_true() interface
>>
>> Documentation/static-keys.txt | 8 ++++++++
>> include/linux/jump_label.h | 30 ++++++++++++++++++++++++++++++
>> kernel/jump_label.c | 40 ++++++++++++++++++++++++++++++++++++++++
>> kernel/sched/core.c | 12 +++++-------
>> kernel/sched/sched.h | 10 +++++-----
>> net/ipv4/udp.c | 9 ++++-----
>> net/ipv6/udp.c | 9 ++++-----
>> 7 files changed, 96 insertions(+), 22 deletions(-)
>>
>



\
 
 \ /
  Last update: 2014-07-01 00:41    [W:0.172 / U:0.504 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site