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  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]
Date:	Wed, 28 May 2014 17:01:41 -0700
From:	Andy Lutomirski <luto@...capital.net>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	Ingo Molnar <mingo@...nel.org>,
	Thomas Gleixner <tglx@...utronix.de>, nicolas.pitre@...aro.org,
	Daniel Lezcano <daniel.lezcano@...aro.org>,
	Mike Galbraith <umgwanakikbuti@...il.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [RFC][PATCH 0/8] sched,idle: need resched polling rework

On Thu, May 22, 2014 at 6:09 AM, Peter Zijlstra <peterz@...radead.org> wrote:
> On Thu, May 22, 2014 at 02:58:18PM +0200, Peter Zijlstra wrote:
>> ---
>> diff --git a/kernel/sched/core.c b/kernel/sched/core.c
>> index 4ea7b3f1a087..a5da85fb3570 100644
>> --- a/kernel/sched/core.c
>> +++ b/kernel/sched/core.c
>> @@ -546,12 +546,38 @@ static bool set_nr_and_not_polling(struct task_struct *p)
>>       struct thread_info *ti = task_thread_info(p);
>>       return !(fetch_or(&ti->flags, _TIF_NEED_RESCHED) & _TIF_POLLING_NRFLAG);
>>  }
>> +
>> +/*
>> + * Atomically set TIF_NEED_RESCHED if TIF_POLLING_NRFLAG is set.
>> + */
>> +static bool set_nr_if_polling(struct task_struct *p)
>> +{
>> +     struct thread_info *ti = task_thread_info(p);
>> +     typeof(ti->flags) old, val = ti->flags;
>> +
>> +     for (;;) {
>> +             if (!(val & _TIF_POLLING_NRFLAG))
>> +                     return false;
>> +             if (val & _TIF_NEED_RESCHED)
>> +                     return true;
>
> Hmm, I think this is racy, false would be safer. If its already set we
> might already be past the sched_ttwu_pending() invocation, while if its
> clear and we're the one to set it, we're guaranteed not.
>
>> +             old = cmpxchg(&ti->flags, val, val | _TIF_NEED_RESCHED);
>> +             if (old == val)
>> +                     return true;
>> +             val = old;
>> +     }
>> +}

Do you have an updated patch?  After fixing the MIME flow damage
(sigh), it doesn't apply to sched/core, which is my best guess for
what it's based on.

--Andy

-- 
Andy Lutomirski
AMA Capital Management, LLC
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/

Powered by blists - more mailing lists