From: Mike Galbraith <umgwanakikbuti@gmail.com>
To: Thomas Gleixner <tglx@linutronix.de>
Cc: LKML <linux-kernel@vger.kernel.org>,
Peter Zijlstra <peterz@infradead.org>,
Ingo Molnar <mingo@elte.hu>, Steven Rostedt <rostedt@goodmis.org>
Subject: Re: RFC: futex_wait() can DoS the tick
Date: Thu, 11 Jun 2015 15:58:36 +0200 [thread overview]
Message-ID: <1434031116.4051.18.camel@gmail.com> (raw)
In-Reply-To: <alpine.DEB.2.11.1506111507560.3786@nanos>
On Thu, 2015-06-11 at 15:13 +0200, Thomas Gleixner wrote:
> What you are looking at is the actual timer interrupt vector, but
> that's not the the tick.
>
> # grep 'expire_entry.*tick_sched_timer' trace2 | wc -l
> 45
>
> 175 / 45 =~ 4 . So I you have CPNFIG_HZ=250
>
> The kernel does not care whether the actual interrupt happens or the
> timer is expired by other means.
Learn something new every day. I (obviously) had no idea that it's
perfectly fine for interrupts to go away when the CPU is busy.
Oh well. Thanks for the new wrinkle in the mush between my ears.
-Mike
next prev parent reply other threads:[~2015-06-11 13:58 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-06-10 12:44 RFC: futex_wait() can DoS the tick Mike Galbraith
2015-06-10 15:12 ` Thomas Gleixner
2015-06-10 16:29 ` Mike Galbraith
2015-06-10 18:27 ` Thomas Gleixner
2015-06-10 17:30 ` Mike Galbraith
2015-06-10 18:59 ` Thomas Gleixner
2015-06-10 19:15 ` Steven Rostedt
2015-06-10 19:32 ` Thomas Gleixner
2015-06-11 2:27 ` Mike Galbraith
2015-06-11 8:34 ` Thomas Gleixner
2015-06-11 11:41 ` Mike Galbraith
2015-06-11 13:13 ` Thomas Gleixner
2015-06-11 13:58 ` Mike Galbraith [this message]
2015-06-11 18:43 ` Mike Galbraith
2015-06-11 18:52 ` Thomas Gleixner
2015-06-11 18:55 ` Mike Galbraith
2015-06-11 7:35 ` Mike Galbraith
2015-06-11 7:43 ` Mike Galbraith
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