On Tue, Jan 12, 2021 at 04:00:57PM +0000, John Garry wrote: ... > > I boot-tested on my machines which have hisi_sas v2 and v3 hw, and it's ok. > I will ask some guys to test a bit more. > Thanks a lot! > And generally the changes look ok. But I just have a slight concern that we > don't pass the gfp_flags all the way from the origin caller. > > So we have some really long callchains, for example: > > host.c: sci_controller_error_handler(): atomic, irq handler (*) > OR host.c: sci_controller_completion_handler(), atomic, tasklet (*) > -> sci_controller_process_completions() > -> sci_controller_unsolicited_frame() > -> phy.c: sci_phy_frame_handler() > -> sci_change_state(SCI_PHY_SUB_AWAIT_SAS_POWER) > -> sci_phy_starting_await_sas_power_substate_enter() > -> host.c: sci_controller_power_control_queue_insert() > -> phy.c: sci_phy_consume_power_handler() > -> sci_change_state(SCI_PHY_SUB_FINAL) > -> sci_change_state(SCI_PHY_SUB_FINAL) > -> sci_controller_event_completion() > -> phy.c: sci_phy_event_handler() > -> sci_phy_start_sata_link_training() > -> sci_change_state(SCI_PHY_SUB_AWAIT_SATA_POWER) > -> sci_phy_starting_await_sata_power_substate_enter > -> host.c: sci_controller_power_control_queue_insert() > -> phy.c: sci_phy_consume_power_handler() > -> sci_change_state(SCI_PHY_SUB_FINAL) > > So if someone rearranges the code later, adds new callchains, etc., it could > be missed that the context may have changed than what we assume at the > bottom. But then passing the flags everywhere is cumbersome, and all the > libsas users see little or no significant changes anyway, apart from a > couple. > The deep call chains like the one you've quoted are all within the isci Intel driver (patches #5 => #7), due to the *massive* state transitions that driver has. But as the commit logs of these three patches show, almost all of such transitions happened under atomic context anyway and GFP_ATOMIC was thus used. The GFP_KERNEL call-chains were all very simple: a workqueue, functions already calling msleep() or wait_event_timeout() two or three lines nearby, and so on. All the other libsas clients (that is, except isci) also had normal call chains that were IMHO easy to follow. Thanks, -- Ahmed S. Darwish Linutronix GmbH
