linux-kernel - Re: [PATCH 6/6] eventpoll: add support for min-wait

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] [day] [month] [year] [list]

Message-ID: <d14164e3-dd51-56f9-9df4-40064fb2a1c2@kernel.dk>
Date:   Thu, 1 Dec 2022 11:41:13 -0700
From:   Jens Axboe <axboe@...nel.dk>
To:     Soheil Hassas Yeganeh <soheil@...gle.com>
Cc:     linux-kernel@...r.kernel.org, netdev@...r.kernel.org,
        Willem de Bruijn <willemb@...gle.com>,
        Shakeel Butt <shakeelb@...gle.com>
Subject: Re: [PATCH 6/6] eventpoll: add support for min-wait

On 12/1/22 11:39 AM, Soheil Hassas Yeganeh wrote:
> On Thu, Dec 1, 2022 at 1:00 PM Jens Axboe <axboe@...nel.dk> wrote:
>>
>>>>> @@ -1845,6 +1891,18 @@ static int ep_poll(struct eventpoll *ep, struct epoll_event __user *events,
>>>>>             ewq.timed_out = true;
>>>>>     }
>>>>>
>>>>> +   /*
>>>>> +    * If min_wait is set for this epoll instance, note the min_wait
>>>>> +    * time. Ensure the lowest bit is set in ewq.min_wait_ts, that's
>>>>> +    * the state bit for whether or not min_wait is enabled.
>>>>> +    */
>>>>> +   if (ep->min_wait_ts) {
>>>>
>>>> Can we limit this block to "ewq.timed_out && ep->min_wait_ts"?
>>>> AFAICT, the code we run here is completely wasted if timeout is 0.
>>>
>>> Yep certainly, I can gate it on both of those conditions.
>> Looking at this for a respin, I think it should be gated on
>> !ewq.timed_out? timed_out == true is the path that it's wasted on
>> anyway.
> 
> Ah, yes, that's a good point. The check should be !ewq.timed_out.

The just posted v4 has the check (and the right one :-))

-- 
Jens Axboe