Re: [PATCH 5/9] Make idr_get_new* rcu-safe

["Paul E. McKenney" <paulmck@linux.vnet.ibm.com>]

On Wed, May 07, 2008 at 01:35:58PM +0200, Nadia.Derbey@bull.net wrote:
> [PATCH 05/09]
> 
> This is a patch that make the idr_get_new* routines rcu-safe.

Reviewed-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>

> Signed-off-by: Nadia Derbey <Nadia.Derbey@bull.net>
> 
> ---
>  lib/idr.c |   17 ++++++++++++-----
>  1 file changed, 12 insertions(+), 5 deletions(-)
> 
> Index: linux-2.6.25-mm1/lib/idr.c
> ===================================================================
> --- linux-2.6.25-mm1.orig/lib/idr.c	2008-05-06 17:38:42.000000000 +0200
> +++ linux-2.6.25-mm1/lib/idr.c	2008-05-06 18:02:07.000000000 +0200
> @@ -6,6 +6,8 @@
>   * Modified by George Anzinger to reuse immediately and to use
>   * find bit instructions.  Also removed _irq on spinlocks.
>   *
> + * Modified by Nadia Derbey to make it RCU safe.
> + *
>   * Small id to pointer translation service.
>   *
>   * It uses a radix tree like structure as a sparse array indexed
> @@ -96,7 +98,7 @@ static void idr_mark_full(struct idr_lay
>   * @gfp_mask:	memory allocation flags
>   *
>   * This function should be called prior to locking and calling the
> - * following function.  It preallocates enough memory to satisfy
> + * idr_get_new* functions. It preallocates enough memory to satisfy
>   * the worst possible allocation.
>   *
>   * If the system is REALLY out of memory this function returns 0,
> @@ -170,7 +172,8 @@ static int sub_alloc(struct idr *idp, in
>  			new = get_from_free_list(idp);
>  			if (!new)
>  				return -1;
> -			p->ary[m] = new;
> +			INIT_RCU_HEAD(&new->rcu_head);
> +			rcu_assign_pointer(p->ary[m], new);
>  			p->count++;
>  		}
>  		pa[l--] = p;
> @@ -195,6 +198,7 @@ build_up:
>  	if (unlikely(!p)) {
>  		if (!(p = get_from_free_list(idp)))
>  			return -1;
> +		INIT_RCU_HEAD(&p->rcu_head);
>  		layers = 1;
>  	}
>  	/*
> @@ -222,11 +226,12 @@ build_up:
>  		}
>  		new->ary[0] = p;
>  		new->count = 1;
> +		INIT_RCU_HEAD(&new->rcu_head);
>  		if (p->bitmap == IDR_FULL)
>  			__set_bit(0, &new->bitmap);
>  		p = new;
>  	}
> -	idp->top = p;
> +	rcu_assign_pointer(idp->top, p);
>  	idp->layers = layers;
>  	v = sub_alloc(idp, &id, pa);
>  	if (v == IDR_NEED_TO_GROW)
> @@ -245,7 +250,8 @@ static int idr_get_new_above_int(struct 
>  		 * Successfully found an empty slot.  Install the user
>  		 * pointer and mark the slot full.
>  		 */
> -		pa[0]->ary[id & IDR_MASK] = (struct idr_layer *)ptr;
> +		rcu_assign_pointer(pa[0]->ary[id & IDR_MASK],
> +				(struct idr_layer *)ptr);
>  		pa[0]->count++;
>  		idr_mark_full(pa, id);
>  	}
> @@ -710,7 +716,8 @@ int ida_get_new_above(struct ida *ida, i
>  			return -EAGAIN;
> 
>  		memset(bitmap, 0, sizeof(struct ida_bitmap));
> -		pa[0]->ary[idr_id & IDR_MASK] = (void *)bitmap;
> +		rcu_assign_pointer(pa[0]->ary[idr_id & IDR_MASK],
> +				(void *)bitmap);
>  		pa[0]->count++;
>  	}
> 
> 
> --