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Message-ID: <53576859.8060706@linutronix.de>
Date: Wed, 23 Apr 2014 09:14:33 +0200
From: Sebastian Andrzej Siewior <bigeasy@...utronix.de>
To: Steven Rostedt <rostedt@...dmis.org>
CC: Stanislav Meduna <stano@...una.org>,
"linux-rt-users@...r.kernel.org" <linux-rt-users@...r.kernel.org>,
Linux ARM Kernel <linux-arm-kernel@...ts.infradead.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
Thomas Gleixner <tglx@...utronix.de>,
Peter Zijlstra <peterz@...radead.org>
Subject: Re: BUG: spinlock trylock failure on UP, i.MX28 3.12.15-rt25
On 04/22/2014 08:16 PM, Steven Rostedt wrote:
> --- a/kernel/timer.c
> +++ b/kernel/timer.c
> @@ -1447,6 +1447,12 @@ static void run_timer_softirq(struct softirq_action *h)
> __run_timers(base);
> }
>
> +#ifdef CONFIG_SMP
> +#define timer_should_raise_softirq(lock) !spin_do_trylock(lock)
> +#else
> +#define timer_should_raise_softirq(lock) 1
> +#endif
> +
No. The lock may be taken but it also may be available no matter if UP
or not. With this patch applied the lockdep splat will go away but the
FULL_NO_HZ people will come back because the timer softirq is scheduled
even if no timer has expired.
Sebastian
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