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From: Peter Zijlstra <peterz@infradead.org>
To: David Ahern <dsahern@gmail.com>
Cc: tglx@linutronix.de, mingo@kernel.org,
	linux-kernel@vger.kernel.org,
	Stephane Eranian <eranian@google.com>
Subject: Re: [PATCH 3/3] perf: Fix mux_interval hrtimer wreckage
Date: Wed, 15 Apr 2015 16:20:02 +0200	[thread overview]
Message-ID: <20150415142002.GR23123@twins.programming.kicks-ass.net> (raw)
In-Reply-To: <552E6C12.8010702@gmail.com>

On Wed, Apr 15, 2015 at 07:48:02AM -0600, David Ahern wrote:
> Hi Peter:
> 
> On 4/15/15 3:41 AM, Peter Zijlstra wrote:
> >Thomas stumbled over the hrtimer_forward_now() in
> >perf_event_mux_interval_ms_store() and noticed its broken-ness.
> >
> >You cannot just change the expiry time of an active timer, it will
> >destroy the red-black tree order and cause havoc.
> >
> >Change it to (re)start the timer instead, (re)starting a timer will
> >dequeue and enqueue a timer and therefore preserve rb-tree order.
> 
> Should this be fixed in stable trees as well?

Hmm, I was going to write how this all relies on the hrtimer rework, but
I think we might just be fine because all this is strictly cpu local and
serialized through irq-disable.

But yes, its can't be worse than it is now.

  reply	other threads:[~2015-04-15 14:20 UTC|newest]

Thread overview: 22+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2015-04-15  9:41 [PATCH 0/3] hrtimer (related) fixes Peter Zijlstra
2015-04-15  9:41 ` [PATCH 1/3] hrtimer: Fix race between hrtimer_start() and __run_hrtimer() Peter Zijlstra
2015-04-15 10:26   ` Thomas Gleixner
2015-04-15 11:31     ` Peter Zijlstra
2015-04-15 11:35       ` Thomas Gleixner
2015-04-15 11:43         ` Peter Zijlstra
2015-04-22 19:15       ` [tip:timers/core] hrtimer: Allow concurrent hrtimer_start() for self restarting timers tip-bot for Peter Zijlstra
2015-05-12 13:52         ` Sasha Levin
2015-05-13 13:43           ` Peter Zijlstra
2015-05-13 13:54             ` Ingo Molnar
2015-05-13 17:25             ` bsegall
2015-05-13 23:09             ` Sasha Levin
2015-05-14 10:23               ` Peter Zijlstra
2015-05-18 15:21                 ` [tip:timers/core] sched,perf: Fix periodic timers tip-bot for Peter Zijlstra
2015-04-15  9:41 ` [PATCH 2/3] sched: Cleanup bandwidth timers Peter Zijlstra
2015-04-16 20:03   ` bsegall
2015-04-22 19:15   ` [tip:timers/core] " tip-bot for Peter Zijlstra
2015-04-15  9:41 ` [PATCH 3/3] perf: Fix mux_interval hrtimer wreckage Peter Zijlstra
2015-04-15 13:48   ` David Ahern
2015-04-15 14:20     ` Peter Zijlstra [this message]
2015-04-22 15:12   ` Thomas Gleixner
2015-04-22 19:15   ` [tip:timers/core] " tip-bot for Peter Zijlstra

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