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Date: Wed, 15 Apr 2015 07:48:02 -0600
From: David Ahern <dsahern@gmail.com>
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To: Peter Zijlstra <peterz@infradead.org>, tglx@linutronix.de
CC: mingo@kernel.org, linux-kernel@vger.kernel.org,
        Stephane Eranian <eranian@google.com>
Subject: Re: [PATCH 3/3] perf: Fix mux_interval hrtimer wreckage
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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?

David