Re: [PATCH 04/14] scsi: qla2xxx: qla82xx: Remove in_interrupt().

[Daniel Wagner <dwagner@suse.de>]

On Thu, Nov 26, 2020 at 02:29:42PM +0100, Sebastian Andrzej Siewior wrote:
> From: "Ahmed S. Darwish" <a.darwish@linutronix.de>
> 
> qla82xx_idc_lock() spins on a certain hardware state until it's 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: qla82xx_idc_lock() is always called
> from process context. Below is an analysis of its callers, in order of
> appearance:
> 
>   - qla_nx.c: qla82xx_device_bootstrap(), only called by
>     qla82xx_device_state_handler(), has multiple msleep()s.
> 
>   - qla_nx.c: qla82xx_need_qsnt_handler(), has one second msleep()
> 
>   - qla_nx.c: qla82xx_wait_for_state_change(), one second msleep()
> 
>   - qla_nx.c: qla82xx_need_reset_handler(), can sleep up to 10 seconds
> 
>   - qla_nx.c: qla82xx_device_state_handler(), has multiple msleep()s
> 
>   - qla_nx.c: qla82xx_abort_isp(), if it's a qla82xx controller, calls
>     qla82xx_device_state_handler(), which sleeps. It's also bound to
>     isp_operations ->abort_isp() hook, where all the callers are in
>     process context.
> 
>   - qla_nx.c: qla82xx_beacon_on(), bound to isp_operations ->beacon_on()
>     hook.  That hook is only called once, in a mutex locked context,
>     from qla2x00_beacon_store().
> 
>   - qla_nx.c: qla82xx_beacon_off(), bound to isp_operations
>     ->beacon_off() hook.  Like ->beacon_on(), it's only called once, in
>     a mutex locked context, from qla2x00_beacon_store().
> 
>   - qla_nx.c: qla82xx_fw_dump(), calls qla2x00_wait_for_chip_reset(),
>     which has msleep() in a loop. It is bound to isp_operations
>     ->fw_dump() hook. That hook *is* called from atomic context at
>     qla_isr.c by multiple interrupt handlers. Nonetheless, it's other
>     controllers interrupt handlers, and not the qla82xx.

qla82xx_msix_default() and qla82xx_msix_rsp_q() call
qla24xx_process_response_queue() which doesn't implement the firmware
dumping.

>   - qla_attr.c: qla2x00_sysfs_write_fw_dump(), and
>     qla2x00_sysfs_write_reset(), process-context sysfs ->write() hooks.
> 
>   - qla_os.c: qla2x00_probe_one(). PCI ->probe(), process context.
> 
>   - qla_os.c: qla2x00_clear_drv_active(), called solely from
>     qla2x00_remove_one(), which is PCI ->remove() hook, process context.
> 
>   - qla_os.c: qla2x00_do_dpc(), kthread function, process context.
> 
> Remove the in_interrupt() check. Change qla82xx_idc_lock() specification
> to a purely process-context function. Mark it with "Context: task, might
> sleep".
> 
> Change qla82xx_idc_lock() implementation to sleep 100ms, instead of a
> schedule(), for each spin. This is more deterministic, and it matches
> the other qla models idc_lock() functions.
> 
> Signed-off-by: Ahmed S. Darwish <a.darwish@linutronix.de>
> Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
> Cc: Nilesh Javali <njavali@marvell.com>
> Cc: <GR-QLogic-Storage-Upstream@marvell.com>

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