linux-kernel - Re: [PATCH] hres_timers_resume must block interrupts

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Message-Id: <1187069790.12828.131.camel@chaos>
Date:	Tue, 14 Aug 2007 07:36:30 +0200
From:	Thomas Gleixner <tglx@...utronix.de>
To:	Joe Korty <joe.korty@...r.com>
Cc:	Ingo Molnar <mingo@...e.hu>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] hres_timers_resume must block interrupts

On Mon, 2007-08-13 at 19:26 -0400, Joe Korty wrote:
> Retrigger_next_event() must be called with interrupts disabled.
> 
> All internal (to hrtimer.c) uses of retrigger_next_event() are correct.
> But the version exported to other files, hres_timers_resume(), does not
> do the IRQ blocking, nor does the (single) external caller of it.
> 
> Rather than require that users of hres_timers_resume() do the IRQ blocking,
> this patch makes the blocking part of the hres_timers_resume() functionality.

Ack.

> (Also remove the meaningless WARN_ON_ONCE() call in hres_timers_resume)

It's not that meaningless. It catched a resume order problem some time
ago.

	tglx

> Signed-off-by: Joe Korty (joe.korty@...r.com)
> 
> Index: 2.6.23-rc3/kernel/hrtimer.c
> ===================================================================
> --- 2.6.23-rc3.orig/kernel/hrtimer.c	2007-08-13 18:30:09.000000000 -0400
> +++ 2.6.23-rc3/kernel/hrtimer.c	2007-08-13 18:38:48.000000000 -0400
> @@ -463,10 +463,11 @@
>   */
>  void hres_timers_resume(void)
>  {
> -	WARN_ON_ONCE(num_online_cpus() > 1);
> +	unsigned long flags;
>  
> -	/* Retrigger the CPU local events: */
> +	local_irq_save(flags);
>  	retrigger_next_event(NULL);
> +	local_irq_restore(flags);
>  }
>  
>  /*
> 

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