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Re: [PATCH] Fix infinite loop in grub_pit_wait()


From: Marco Gerards
Subject: Re: [PATCH] Fix infinite loop in grub_pit_wait()
Date: Thu, 07 Aug 2008 18:26:34 +0200
User-agent: Gnus/5.110006 (No Gnus v0.6) Emacs/21.4 (gnu/linux)

Christian Franke <address@hidden> writes:

> grub2 from current SVN hangs if run in VirtualPC, the problem was
> introduced with 'svn diff -r 1779:1780'.
>
> Here is a proposed fix.
>
> Christian
>
> 2008-08-07  Christian Franke  <address@hidden>
>
>       * kern/i386/pit.c (TIMER2_SPEAKER): New define.
>       (TIMER2_GATE): Likewise.
>       (grub_pit_wait): Add enable/disable of the timer2 gate
>       bit of port 0x61. This fixes a possible infinite loop.

Small nitpick: use a double space

> diff --git a/kern/i386/pit.c b/kern/i386/pit.c
> index d0a6eda..a3fab26 100644
> --- a/kern/i386/pit.c
> +++ b/kern/i386/pit.c
> @@ -28,13 +28,26 @@
>  #define TIMER_ENABLE_LSB     0x20
>  #define TIMER_ENABLE_MSB     0x10
>  #define TIMER2_LATCH         0x20
> +#define TIMER2_SPEAKER               0x02
> +#define TIMER2_GATE          0x01
>  
>  void
>  grub_pit_wait (grub_uint16_t tics)
>  {
> +  /* Disable timer2 gate and speaker.  */
> +  grub_outb (grub_inb (TIMER2_REG_LATCH) & ~ (TIMER2_SPEAKER | TIMER2_GATE), 
> TIMER2_REG_LATCH);
> +
> +  /* Set tics.  */
>    grub_outb (TIMER2_SELECT | TIMER_ENABLE_LSB | TIMER_ENABLE_MSB, 
> TIMER_REG_COMMAND);
>    grub_outb (tics & 0xff, TIMER2_REG_CONTROL);
>    grub_outb (tics >> 8, TIMER2_REG_CONTROL);
>  
> +  /* Enable timer2 gate, keep speaker disabled.  */
> +  grub_outb ((grub_inb (TIMER2_REG_LATCH) & ~ TIMER2_SPEAKER) | TIMER2_GATE, 
> TIMER2_REG_LATCH);
> +
> +  /* Wait.  */
>    while ((grub_inb (TIMER2_REG_LATCH) & TIMER2_LATCH) == 0x00);
> +
> +  /* Disable timer2 gate and speaker.  */
> +  grub_outb (grub_inb (TIMER2_REG_LATCH) & ~ (TIMER2_SPEAKER | TIMER2_GATE), 
> TIMER2_REG_LATCH);
These lines are too long, please break them properly.



--
Marco





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