Messages in this thread | | | Subject | Re: [PATCH v2 00/19] scsi: libsas: Remove in_interrupt() check | From | John Garry <> | Date | Thu, 14 Jan 2021 09:51:35 +0000 |
| |
On 12/01/2021 17:33, Ahmed S. Darwish wrote: > 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.
To me, the series looks fine. Well, the end result - I didn't go through patch by patch. So:
Reviewed-by: John Garry <john.garry@huawei.com>
I'm still hoping some guys are testing a bit for me, but I'll let you know if any problem.
As an aside, your analysis showed some quite poor usage of spinlocks in some drivers, specifically grabbing a lock and then calling into a depth of 3 or 4 functions.
Thanks, John
| |