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From: Thomas Gleixner <tglx@linutronix.de>
To: Oleg Nesterov <oleg@redhat.com>
Cc: Eric Dumazet <eric.dumazet@gmail.com>,
	Andi Kleen <ak@linux.intel.com>, Andi Kleen <andi@firstfloor.org>,
	LKML <linux-kernel@vger.kernel.org>,
	Andrew Morton <akpm@linux-foundation.org>,
	Peter Zijlstra <peterz@infradead.org>
Subject: Re: [PATCH 4/4] posix-timers: turn it_signal into it_valid flag
Date: Wed, 21 Sep 2011 19:56:04 +0200 (CEST)	[thread overview]
Message-ID: <alpine.LFD.2.02.1109211954430.2723@ionos> (raw)
In-Reply-To: <alpine.LFD.2.02.1109211835550.2723@ionos>

On Wed, 21 Sep 2011, Thomas Gleixner wrote:

> On Wed, 7 Sep 2011, Oleg Nesterov wrote:
> > On 09/06, Thomas Gleixner wrote:
> > >
> > > On Tue, 6 Sep 2011, Oleg Nesterov wrote:
> > >
> > > > But how this can help? Suppose that the task is preempted right
> > > > after dequeue_signal() drops ->siglock. We need rcu_read_lock()
> > > > before unlock then, no?
> > >
> > > Crap, you are right, but that's fortunately an easy to solve one :)
> > 
> > Yes, this is solvable. But I think we can do something better.
> > 
> > > > And. This breaks the accounting logic. I mean the patch from Andi
> > > > which adds the limits.
> > >
> > > That's a different problem and really, it does not break it by any
> > > means. When the timer is released, then the count is decreased and we
> > > can safely assume that the memory is going to be freed in the next
> > > grace period.
> > 
> > Yes, but this means we need the counter which we do not have.
> > 
> > I think we can avoid this problems. Although I am not sure, I am
> > already sleeping.
> > 
> > 	- we add rcu_read_lock() into dequeueu_signal().
> > 
> > 	- we add the new "struct k_itimer *my_timer" member into
> > 	 siginfo._timer. Like _sys_private it is not passed to
> > 	 user, and perhaps we can kill _sys_private later.
> 
> sys_private is ugly as hell and we should avoid to add another field
> to siginfo.
> 
> I think we can embed the timer siginfo into k_itimer instead and

That should be sigqeue of course, which has siginfo embedded.

Thanks,

	tglx
 

  reply	other threads:[~2011-09-21 17:56 UTC|newest]

Thread overview: 40+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2011-08-29 23:39 [PATCH 1/4] posix-timers: move global timer id management to signal_struct v2 Andi Kleen
2011-08-29 23:39 ` [PATCH 2/4] posix-timers: limit the number of posix timers per process Andi Kleen
2011-08-30 21:44   ` Andrew Morton
2011-08-30 22:06     ` Andi Kleen
2011-08-30 22:22       ` Andrew Morton
2011-08-30 22:47         ` Andi Kleen
2011-08-30 23:02           ` Andrew Morton
2011-08-31  6:45             ` Jiri Slaby
2011-09-02  9:30   ` Thomas Gleixner
2011-08-29 23:39 ` [PATCH 3/4] posix-timers: Don't disable interrupts in idr_lock Andi Kleen
2011-08-29 23:39 ` [PATCH 4/4] posix-timers: turn it_signal into it_valid flag Andi Kleen
2011-09-02 10:06   ` Thomas Gleixner
2011-09-02 11:49     ` Eric Dumazet
2011-09-02 14:19       ` Thomas Gleixner
2011-09-04 16:56     ` Oleg Nesterov
2011-09-04 19:07       ` Andi Kleen
2011-09-04 20:29       ` Oleg Nesterov
2011-09-06  3:14         ` Andi Kleen
2011-09-06 14:51           ` Oleg Nesterov
2011-09-06 15:39             ` Eric Dumazet
2011-09-06 16:27               ` Oleg Nesterov
2011-09-06 18:47               ` Thomas Gleixner
2011-09-06 18:49                 ` Oleg Nesterov
2011-09-06 19:16                   ` Thomas Gleixner
2011-09-06 19:26                     ` Oleg Nesterov
2011-09-06 19:45                       ` Thomas Gleixner
2011-09-06 22:08                         ` Oleg Nesterov
2011-09-06 22:34                           ` Thomas Gleixner
2011-09-21 16:46                           ` Thomas Gleixner
2011-09-21 17:56                             ` Thomas Gleixner [this message]
2011-09-22 11:19                               ` Thomas Gleixner
2011-09-06 19:30                     ` Eric Dumazet
2011-09-06 20:10                       ` Thomas Gleixner
2011-09-06 20:27                         ` Eric Dumazet
2011-09-06 19:04                 ` Eric Dumazet
2011-08-31  8:53 ` [PATCH 1/4] posix-timers: move global timer id management to signal_struct v2 Eric Dumazet
2011-08-31 16:57   ` Andi Kleen
2011-09-02  9:19 ` Thomas Gleixner
2011-09-02 10:05   ` Eric Dumazet
2011-09-19 21:46   ` Andi Kleen

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