On 07/03/2012 06:15 AM, Seth Jennings wrote:
> Add information on the usage limits of zs_map_object()
>
> Signed-off-by: Seth Jennings <sjenning@xxxxxxxxxxxxxxxxxx>
> ---
> drivers/staging/zsmalloc/zsmalloc-main.c | 7 ++++++-
> 1 file changed, 6 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/staging/zsmalloc/zsmalloc-main.c b/drivers/staging/zsmalloc/zsmalloc-main.c
> index 4942d41..abf7c13 100644
> --- a/drivers/staging/zsmalloc/zsmalloc-main.c
> +++ b/drivers/staging/zsmalloc/zsmalloc-main.c
> @@ -747,7 +747,12 @@ EXPORT_SYMBOL_GPL(zs_free);
> *
> * Before using an object allocated from zs_malloc, it must be mapped using
> * this function. When done with the object, it must be unmapped using
> - * zs_unmap_object
> + * zs_unmap_object.
> + *
> + * Only one object can be mapped per cpu at a time. There is no protection
> + * against nested mappings.
> + *
> + * This function returns with preemption and page faults disabled.
> */
> void *zs_map_object(struct zs_pool *pool, unsigned long handle)
> {
>
The comment is good but I hope we can detect it automatically with DEBUG
option. It wouldn't be hard but it's a debug patch so not critical
until we receive some report about the bug.
The possibility for nesting is that it is used by irq context.
A uses the mapping
.
.
.
IRQ happen
B uses the mapping in IRQ context
.
.
.
Maybe we need local_irq_save/restore in zs_[un]map_object path.
--
Kind regards,
Minchan Kim
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