On Wednesday 10 October 2012 12:25:58 David Laight wrote: > > On Wed, Oct 10, 2012 at 6:08 PM, Oliver Neukum <oneukum@xxxxxxx> wrote: > > > > > 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 > > > > IMO, it is not practical to obey the rule for drivers, because driver may > > call many other kernel component API which may allocate memory > > via GFP_KERNEL in the path easily. > > What about the error handler/sleep/resume code calling into the > memory allocator to indicate that all allocates be GFP_NOIO until > it calls back to indicate that the restricted path is complete. This seems to be a very complex scheme. > Might be a per-cpu count? No. The handlers may sleep and switch CPUs. 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
