On 02/10/2014 02:30 PM, Mike Snitzer wrote: > On Tue, Feb 04 2014 at 6:31am -0500, > Hannes Reinecke <hare@xxxxxxx> wrote: > >> On 02/04/2014 12:26 PM, Junichi Nomura wrote: >>> On 02/04/14 19:54, Hannes Reinecke wrote: >>>> We only need to take care to add a small delay when calling >>>> __pg_init_all_paths() to move processing off to a workqueue; otherwise >>>> pg_init_done() might end up calling scsi_dh_activate() directly, which >>>> might use non-atomic memory allocations or issue I/O. >>> >>> Hi Hannes, >>> >>> could you tell me how "might end up calling scsi_dh_active()" happens? >>> >>> queue_delayed_work() >>> queue_delayed_work_on() >>> __queue_delayed_work() >>> if (!delay) >>> __queue_work() >>> get_work_pool() >>> insert_work() >>> set_work_pwq() >>> get_pwq() >>> if (__need_more_worker()) >>> wake_up_worker() >>> >>> queue_work() doesn't execute the work itself. >>> >>> What am I missing? >>> >> As mentioned, I stumbled across the same issue when developing the >> asynchronous SCSI aborts. I'll see to have it recreated with this >> patchset. > > Just to verify, this seems to be the only outstanding question for this > patchset? > > What value are you using for HZ? If this portion of the change does > turn out to be meaningul: Rather than tieing to HZ should we just use an > explicitly non-zero value for __pg_init_all_paths()'s @min_delay? > The actual amount here is irrelevant, as long as it's non-zero. It's just there to force execution of the work item off the current thread. Cheers, Hannes -- Dr. Hannes Reinecke zSeries & Storage hare@xxxxxxx +49 911 74053 688 SUSE LINUX Products GmbH, Maxfeldstr. 5, 90409 Nürnberg GF: J. Hawn, J. Guild, F. Imendörffer, HRB 16746 (AG Nürnberg) -- dm-devel mailing list dm-devel@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/dm-devel
