Re: [PATCH 07/14] scsi: qla4xxx: qla4_82xx_idc_lock(): Remove in_interrupt().

Daniel Wagner
2020-11-30T14:21:13Z

On Thu, Nov 26, 2020 at 02:29:45PM +0100, Sebastian Andrzej Siewior wrote:
> From: "Ahmed S. Darwish" <a.darwish@linutronix.de>
>
> qla4_82xx_idc_lock() spins on a certain hardware state until it is
> updated. At the end of each spin, if in_interrupt() is true, it does 20
> loops of cpu_relax(). Otherwise, it yields the CPU.
>
> While in_interrupt() is ill-defined and does not provide what the name
> suggests, it is not needed here: qla4_82xx_idc_lock() is always called
> from process context. Below is an analysis of its callers:
>
> - ql4_nx.c: qla4_82xx_need_reset_handler(), 1-second msleep() in a
> loop.
>
> - ql4_nx.c: qla4_82xx_isp_reset(), calls
> qla4_8xxx_device_state_handler(), which has multiple msleep()s.
>
> Beside direct calls, qla4_82xx_idc_lock() is also bound to
> isp_operations ->idc_lock() hook. Other functions which are bound to the
> same hook, e.g. qla4_83xx_drv_lock(), also have an msleep(). For
> completeness, below is an analysis of all callers of that hook:
>
> - ql4_83xx.c: qla4_83xx_need_reset_handler(), has an msleep()
>
> - ql4_83xx.c: qla4_83xx_isp_reset(), calls
> qla4_8xxx_device_state_handler(), which has multiple msleep()s.
>
> - ql4_83xx.c: qla4_83xx_disable_pause(), all process context callers:
> => ql4_mbx.c: qla4xxx_mailbox_command(), msleep(), mutex_lock()
> => ql4_os.c: qla4xxx_recover_adapter(), schedule_timeout() in loop
> => ql4_os.c: qla4xxx_do_dpc(), workqueue context
>
> - ql4_attr.c: qla4_8xxx_sysfs_write_fw_dump(), sysfs bin_attribute
> ->write() hook, process context
>
> - ql4_mbx.c: qla4xxx_mailbox_command(), earlier discussed
>
> - ql4_nx.c: qla4_8xxx_device_bootstrap(), callers:
> => ql4_83xx.c: qla4_83xx_need_reset_handler(), process, msleep()
> => ql4_nx.c: qla4_8xxx_device_state_handler(), earlier discussed
>
> - ql4_nx.c: qla4_8xxx_need_qsnt_handler(), callers:
> => ql4_nx.c: qla4_8xxx_device_state_handler(), multipe msleep()s
> => ql4_os.c: qla4xxx_do_dpc(), workqueue context
>
> - ql4_nx.c: qla4_8xxx_update_idc_reg(), callers:
> => ql4_nx.c: qla4_8xxx_device_state_handler(), earlier discussed
> => ql4_os.c: qla4_8xxx_error_recovery(), only called by
> qla4xxx_pci_slot_reset(), which is bound to PCI ->slot_reset()
> process-context hook
>
> - ql4_nx.c: qla4_8xxx_device_state_handler(), earlier discussed
>
> - ql4_os.c: qla4xxx_recover_adapter(), earlier discussed
>
> - ql4_os.c: qla4xxx_do_dpc(), earlier discussed
>
> Remove the in_interrupt() check. Mark, qla4_82xx_idc_lock(), and the
> ->idc_lock() hook itself, with "Context: task, can sleep".
>
> Change qla4_82xx_idc_lock() implementation to sleep 100ms, instead of a
> schedule(), for each spin. This is more deterministic, and it matches
> other PCI HW locking functions in the driver.
>
> Signed-off-by: Ahmed S. Darwish <a.darwish@linutronix.de>
> Cc: Nilesh Javali <njavali@marvell.com>
> Cc: Manish Rangankar <mrangankar@marvell.com>
> Cc: <GR-QLogic-Storage-Upstream@marvell.com>
> Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>

Reviewed-by: Daniel Wagner <dwagner@suse.de>