On Wednesday 10 October 2012 17:48:54 Ming Lei wrote: > On Wed, Oct 10, 2012 at 4:39 PM, Oliver Neukum <oneukum@xxxxxxx> wrote: > > On Wednesday 10 October 2012 16:17:25 Ming Lei wrote: > >> On Wed, Oct 10, 2012 at 1:51 PM, Oliver Neukum <oneukum@xxxxxxx> wrote: > > > >> > We need to use GFP_NOIO in situations the helper cannot know about. > >> > Please add a gfp_t parameter. Then the caller will solve that. > >> > >> Considered that most of drivers call the helpers in different context, I think > >> it is better to switch the gpf_t flag runtime inside helpers, like below: > >> > >> if (dev->power.runtime_status == RPM_RESUMING) > >> gfp = GFP_NOIO; > >> else > >> gfp = GFP_KERNEL; > > > > You are admirably persistent ;-) > > I am only trying to solve the problem more generally, :-) The most generic solution is passing the parameter. > > If you extended the check to RPM_SUSPENDING it might work, > > but still the problem with error handling exists. > > Could you describe the error handling case in a bit detail so > that callers of these helpers can know when GFP_KERNEL > is to be passed and when GFP_NOIO is taken if the gfp > patamerer has to be added? A reset always applies to the whole device. Resets are used in error handling of block devices (storage and uas). If you reset a device, pre_reset() and post_reset() of all interfaces need to be called. So they are part of the SCSI error handler. SCSI error handlers can allocate memory only with GFP_NOIO (or GFP_ATOMIC) because any IO for paging can cause the SCSI layer to wait for the error handling to finish. The error handling can only finish when pre/post_reset() have finished. Catch-22 So any control messages in block error handling need to use GFP_NOIO. If you look at the control message helpers in usbcore you will find a lot of GFP_NOIO. That is the reason. Regards Oliver -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
