* [PATCH] scsi: cxlflash: Select SCSI_SCAN_ASYNC
@ 2018-02-19 7:10 Vaibhav Jain
2018-02-20 8:56 ` Michael Ellerman
0 siblings, 1 reply; 3+ messages in thread
From: Vaibhav Jain @ 2018-02-19 7:10 UTC (permalink / raw)
To: Manoj N . Kumar
Cc: Vaibhav Jain, Matthew R . Ochs, Uma Krishnan, linux-scsi,
linux-kernel, Frederic Barrat, linuxppc-dev
The cxlflash driver uses "Asynchronous SCSI scanning" enabled by
CONFIG_SCSI_SCAN_ASYNC. Without this enabled the modprobe of cxlflash
module gets hung with following backtrace:
Call Trace:
__switch_to+0x2cc/0x470
__schedule+0x288/0xab0
schedule+0x40/0xc0
schedule_timeout+0x254/0x4f0
wait_for_common+0xdc/0x260
flush_work+0x140/0x2a0
work_on_cpu+0x88/0xb0
pci_device_probe+0x1d0/0x220
driver_probe_device+0x408/0x5b0
__driver_attach+0x16c/0x1a0
bus_for_each_dev+0xb8/0x110
driver_attach+0x3c/0x60
bus_add_driver+0x1d8/0x370
driver_register+0x9c/0x180
__pci_register_driver+0x74/0xa0
init_cxlflash+0x158/0x1cc
do_one_initcall+0x68/0x1e0
do_init_module+0x90/0x254
load_module+0x2f8c/0x3720
SyS_finit_module+0xcc/0x140
system_call+0x58/0x6c
Signed-off-by: Vaibhav Jain <vaibhav@linux.vnet.ibm.com>
---
drivers/scsi/cxlflash/Kconfig | 1 +
1 file changed, 1 insertion(+)
diff --git a/drivers/scsi/cxlflash/Kconfig b/drivers/scsi/cxlflash/Kconfig
index a011c5dbf214..f054c1b0fff3 100644
--- a/drivers/scsi/cxlflash/Kconfig
+++ b/drivers/scsi/cxlflash/Kconfig
@@ -6,6 +6,7 @@ config CXLFLASH
tristate "Support for IBM CAPI Flash"
depends on PCI && SCSI && CXL && EEH
select IRQ_POLL
+ select SCSI_SCAN_ASYNC
default m
help
Allows CAPI Accelerated IO to Flash
--
2.14.3
^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: [PATCH] scsi: cxlflash: Select SCSI_SCAN_ASYNC
2018-02-19 7:10 [PATCH] scsi: cxlflash: Select SCSI_SCAN_ASYNC Vaibhav Jain
@ 2018-02-20 8:56 ` Michael Ellerman
2018-02-21 3:23 ` Matthew R. Ochs
0 siblings, 1 reply; 3+ messages in thread
From: Michael Ellerman @ 2018-02-20 8:56 UTC (permalink / raw)
To: Vaibhav Jain, Manoj N . Kumar
Cc: linux-scsi, Matthew R . Ochs, Vaibhav Jain, Frederic Barrat,
linux-kernel, Uma Krishnan, linuxppc-dev
Vaibhav Jain <vaibhav@linux.vnet.ibm.com> writes:
> The cxlflash driver uses "Asynchronous SCSI scanning" enabled by
> CONFIG_SCSI_SCAN_ASYNC. Without this enabled the modprobe of cxlflash
> module gets hung with following backtrace:
>
> Call Trace:
> __switch_to+0x2cc/0x470
> __schedule+0x288/0xab0
> schedule+0x40/0xc0
> schedule_timeout+0x254/0x4f0
> wait_for_common+0xdc/0x260
> flush_work+0x140/0x2a0
> work_on_cpu+0x88/0xb0
> pci_device_probe+0x1d0/0x220
> driver_probe_device+0x408/0x5b0
> __driver_attach+0x16c/0x1a0
> bus_for_each_dev+0xb8/0x110
> driver_attach+0x3c/0x60
> bus_add_driver+0x1d8/0x370
> driver_register+0x9c/0x180
> __pci_register_driver+0x74/0xa0
> init_cxlflash+0x158/0x1cc
> do_one_initcall+0x68/0x1e0
> do_init_module+0x90/0x254
> load_module+0x2f8c/0x3720
> SyS_finit_module+0xcc/0x140
> system_call+0x58/0x6c
Why does it "hang"? That's kind of bizarre, I would expect either a
build or runtime failure if a feature the driver requires is missing.
> diff --git a/drivers/scsi/cxlflash/Kconfig b/drivers/scsi/cxlflash/Kconfig
> index a011c5dbf214..f054c1b0fff3 100644
> --- a/drivers/scsi/cxlflash/Kconfig
> +++ b/drivers/scsi/cxlflash/Kconfig
> @@ -6,6 +6,7 @@ config CXLFLASH
> tristate "Support for IBM CAPI Flash"
> depends on PCI && SCSI && CXL && EEH
> select IRQ_POLL
> + select SCSI_SCAN_ASYNC
It's user configurable, so it's rude to select it. It can also be
disabled on the kernel command line, so this seems like a fragile
solution.
cheers
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH] scsi: cxlflash: Select SCSI_SCAN_ASYNC
2018-02-20 8:56 ` Michael Ellerman
@ 2018-02-21 3:23 ` Matthew R. Ochs
0 siblings, 0 replies; 3+ messages in thread
From: Matthew R. Ochs @ 2018-02-21 3:23 UTC (permalink / raw)
To: Michael Ellerman
Cc: Vaibhav Jain, Manoj N . Kumar, linux-scsi, Frederic Barrat,
linux-kernel, Uma Krishnan, linuxppc-dev
On Tue, Feb 20, 2018 at 07:56:35PM +1100, Michael Ellerman wrote:
> Vaibhav Jain <vaibhav@linux.vnet.ibm.com> writes:
>
> > The cxlflash driver uses "Asynchronous SCSI scanning" enabled by
> > CONFIG_SCSI_SCAN_ASYNC. Without this enabled the modprobe of cxlflash
> > module gets hung with following backtrace:
> >
> > Call Trace:
> > __switch_to+0x2cc/0x470
> > __schedule+0x288/0xab0
> > schedule+0x40/0xc0
> > schedule_timeout+0x254/0x4f0
> > wait_for_common+0xdc/0x260
> > flush_work+0x140/0x2a0
> > work_on_cpu+0x88/0xb0
> > pci_device_probe+0x1d0/0x220
> > driver_probe_device+0x408/0x5b0
> > __driver_attach+0x16c/0x1a0
> > bus_for_each_dev+0xb8/0x110
> > driver_attach+0x3c/0x60
> > bus_add_driver+0x1d8/0x370
> > driver_register+0x9c/0x180
> > __pci_register_driver+0x74/0xa0
> > init_cxlflash+0x158/0x1cc
> > do_one_initcall+0x68/0x1e0
> > do_init_module+0x90/0x254
> > load_module+0x2f8c/0x3720
> > SyS_finit_module+0xcc/0x140
> > system_call+0x58/0x6c
>
> Why does it "hang"? That's kind of bizarre, I would expect either a
> build or runtime failure if a feature the driver requires is missing.
>
It hangs due to a bug in the driver. I briefly looked at it several
months back before getting distracted with other items. IIRC there
was an issue with the state machine.
> > diff --git a/drivers/scsi/cxlflash/Kconfig b/drivers/scsi/cxlflash/Kconfig
> > index a011c5dbf214..f054c1b0fff3 100644
> > --- a/drivers/scsi/cxlflash/Kconfig
> > +++ b/drivers/scsi/cxlflash/Kconfig
> > @@ -6,6 +6,7 @@ config CXLFLASH
> > tristate "Support for IBM CAPI Flash"
> > depends on PCI && SCSI && CXL && EEH
> > select IRQ_POLL
> > + select SCSI_SCAN_ASYNC
>
> It's user configurable, so it's rude to select it. It can also be
> disabled on the kernel command line, so this seems like a fragile
> solution.
>
I think Vaibhav's intention here was to avoid the hang while the bug
is still present - I believe he has encountered it several times recently.
The proper solution would be to fix the bug.
^ permalink raw reply [flat|nested] 3+ messages in thread
end of thread, other threads:[~2018-02-21 3:23 UTC | newest]
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2018-02-19 7:10 [PATCH] scsi: cxlflash: Select SCSI_SCAN_ASYNC Vaibhav Jain
2018-02-20 8:56 ` Michael Ellerman
2018-02-21 3:23 ` Matthew R. Ochs
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