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 <sjenn...@linux.vnet.ibm.com> > --- > 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 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/