Messages in this thread | | | Date | Thu, 23 Nov 2017 17:27:18 -0500 (EST) | From | Mikulas Patocka <> | Subject | Re: [dm-devel] [PATCH 1/2] swait: export the symbols __prepare_to_swait and __finish_swait |
| |
On Thu, 23 Nov 2017, Christoph Hellwig wrote:
> Please run this past the swait authors. It is supposed to be a simple > and self-contained API so I'd expect this patch to be seen critical.
I already sent it to Peter Zijlstra and didn't get a response yet.
> You might be better off to just use the normal complex waitqueues if > you want to micro-optimize like this.
If we wanted to micro-optimize, we should use the simpler wait queue variant.
If these functions are not supposed to be used by others, then - why are they in in file swait.h? - why does the implementation export swake_up_locked which assumes that someone else will lock the spinlock before calling it?
> On Wed, Nov 22, 2017 at 09:35:36PM -0500, Mikulas Patocka wrote: > > In order to reduce locking overhead, I use the spinlock in > > swait_queue_head to protect not only the wait queue, but also the list of > > events. Consequently, I need to use unlocked functions __prepare_to_swait > > and __finish_swait. These functions are declared in the file > > include/linux/swait.h, but they are not exported, and so they are not > > useable from kernel modules. > > > > Signed-off-by: Mikulas Patocka <mpatocka@redhat.com> > > > > --- > > kernel/sched/swait.c | 2 ++ > > 1 file changed, 2 insertions(+) > > > > Index: linux-2.6/kernel/sched/swait.c > > =================================================================== > > --- linux-2.6.orig/kernel/sched/swait.c > > +++ linux-2.6/kernel/sched/swait.c > > @@ -73,6 +73,7 @@ void __prepare_to_swait(struct swait_que > > if (list_empty(&wait->task_list)) > > list_add(&wait->task_list, &q->task_list); > > } > > +EXPORT_SYMBOL(__prepare_to_swait); > > > > void prepare_to_swait(struct swait_queue_head *q, struct swait_queue *wait, int state) > > { > > @@ -102,6 +103,7 @@ void __finish_swait(struct swait_queue_h > > if (!list_empty(&wait->task_list)) > > list_del_init(&wait->task_list); > > } > > +EXPORT_SYMBOL(__finish_swait); > > > > void finish_swait(struct swait_queue_head *q, struct swait_queue *wait) > > { > > > > -- > > dm-devel mailing list > > dm-devel@redhat.com > > https://www.redhat.com/mailman/listinfo/dm-devel > ---end quoted text--- >
| |