From: Thomas Gleixner <tglx@linutronix.de>
To: Sasha Levin <levinsasha928@gmail.com>
Cc: John Stultz <john.stultz@linaro.org>,
Dave Jones <davej@redhat.com>,
"linux-kernel@vger.kernel.org List"
<linux-kernel@vger.kernel.org>,
Peter Zijlstra <peterz@infradead.org>
Subject: Re: ntp: BUG: spinlock lockup on CPU#1
Date: Thu, 15 Mar 2012 15:58:20 +0100 (CET) [thread overview]
Message-ID: <alpine.LFD.2.02.1203151556090.2466@ionos> (raw)
In-Reply-To: <alpine.LFD.2.02.1203151440590.2466@ionos>
On Thu, 15 Mar 2012, Thomas Gleixner wrote:
> CPU 0 CPU 1
> do_adjtimex()
> spin_lock_irq(&ntp_lock);
> process_adjtimex_modes(); timer_interrupt()
> process_adj_status(); do_timer()
> ntp_start_leap_timer(); write_lock(&xtime_lock);
> hrtimer_start(); update_wall_time();
> hrtimer_reprogram(); ntp_tick_length()
> tick_program_event() spin_lock(&ntp_lock);
> clockevents_program_event()
> ktime_get()
> seq = req_seqbegin(xtime_lock);
>
> So CPU0 waits for xtime seqence to become valid and CPU1 cant make
> progress because it's stuck on ntp_lock.
The same problem exists with ntp_clear() being called under the
xtime/timekeeper lock write locked. Nasty ...
prev parent reply other threads:[~2012-03-15 14:58 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-03-15 13:23 ntp: BUG: spinlock lockup on CPU#1 Sasha Levin
2012-03-15 13:28 ` Sasha Levin
2012-03-15 14:04 ` Thomas Gleixner
2012-03-15 14:52 ` Sasha Levin
2012-03-15 14:03 ` Thomas Gleixner
2012-03-15 14:58 ` Thomas Gleixner [this message]
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