Messages in this thread | | | Subject | Re: [PATCH] libsas: flush pending destruct work in sas_unregister_domain_devices() | From | John Garry <> | Date | Thu, 7 Dec 2017 13:37:53 +0000 |
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On 28/11/2017 17:04, Cong Wang wrote: > On Tue, Nov 28, 2017 at 3:18 AM, John Garry <john.garry@huawei.com> wrote: >> On 28/11/2017 08:20, Johannes Thumshirn wrote: >>> >>> On Mon, Nov 27, 2017 at 04:24:45PM -0800, Cong Wang wrote: >>>> >>>> We saw dozens of the following kernel waring: >>>> >>>> WARNING: CPU: 0 PID: 705 at fs/sysfs/group.c:224 >>>> sysfs_remove_group+0x54/0x88() >>>> sysfs group ffffffff81ab7670 not found for kobject '6:0:3:0' >>>> Modules linked in: cpufreq_ondemand x86_pkg_temp_thermal coretemp >>>> kvm_intel kvm microcode raid0 iTCO_wdt iTCO_vendor_support sb_edac edac_core >>>> lpc_ich mfd_core ioatdma i2c_i801 shpchp wmi hed acpi_cpufreq lp parport >>>> tcp_diag inet_diag ipmi_si ipmi_devintf ipmi_msghandler sch_fq_codel igb ptp >>>> pps_core i2c_algo_bit i2c_core crc32c_intel isci libsas scsi_transport_sas >>>> dca ipv6 >>>> CPU: 0 PID: 705 Comm: kworker/u240:0 Not tainted 4.1.35.el7.x86_64 #1 >>> >>> >>> This should by now be fixed with commit fbce4d97fd43 ("scsi: fixup kernel >>> warning during rmmod()" which went into v4.14-rc6. >>> >> >> Is that the same issue? I think Cong Wang is just trying to deal with the >> longstanding libsas hotplug WARN. > > Right, we saw it on both 4.1 and 3.14, clearly an old bug. > > >> >> We at Huawei are still working to fix it. Our patchset is under internal >> test at the moment. >> >> As for this patch: >>> drivers/scsi/libsas/sas_discover.c | 7 ++++++- >>> 1 file changed, 6 insertions(+), 1 deletion(-) >>> >>> diff --git a/drivers/scsi/libsas/sas_discover.c >>> b/drivers/scsi/libsas/sas_discover.c >>> index 60de66252fa2..27c11fc7aa2b 100644 >>> --- a/drivers/scsi/libsas/sas_discover.c >>> +++ b/drivers/scsi/libsas/sas_discover.c >>> @@ -388,6 +388,11 @@ void sas_unregister_dev(struct asd_sas_port *port, >>> struct domain_device *dev) >>> } >>> } >>> >>> +static void sas_flush_work(struct asd_sas_port *port) >>> +{ >>> + scsi_flush_work(port->ha->core.shost); >>> +} >>> + >>> void sas_unregister_domain_devices(struct asd_sas_port *port, int gone) >>> { >>> struct domain_device *dev, *n; >>> @@ -401,8 +406,8 @@ void sas_unregister_domain_devices(struct asd_sas_port >>> *port, int gone) >>> list_for_each_entry_safe(dev, n, &port->disco_list, disco_list_node) >>> sas_unregister_dev(port, dev); >>> >>> + sas_flush_work(port); >> >> How can this work as sas_unregister_domain_devices() may be called from the >> same workqueue which you're trying to flush? >
Sorry for slow reply, just remembered this now.
> > I don't understand, the only caller of sas_unregister_domain_devices() > is sas_deform_port(). >
And sas_deform_port() may be called from another worker on the same queue, right? As in sas_phye_loss_of_signal()->sas_deform_port()
As I see today, this is the problem callchain: sas_deform_port() sas_unregister_domain_devices() sas_unregister_dev() sas_discover_event(DISCE_DESTRUCT)
The device destruct takes place in a separate worker from which sas_deform_port() is called, but the same queue. So we have this queued destruct happen after the port is fully deformed -> hence the WARN.
I guess you only tested your patch on disks attached through an expander.
Thanks, John
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