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Subject[PATCH] libsas: flush pending destruct work in sas_unregister_domain_devices()
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
Hardware name: WIWYNN Lyra/JD/S2600GZ, BIOS SE5C600.86B.02.03.2004.030620151456 03/06/2015
Workqueue: scsi_wq_6 sas_destruct_devices [libsas]
0000000000000000 ffff88056c393ba8 ffffffff81544a6d ffff88056c393bf8
0000000000000009 ffff88056c393be8 ffffffff81069b4c ffff88081790d078
ffffffff811dad37 0000000000000000 ffffffff81ab7670 ffff88081b29dc10
Call Trace:
[<ffffffff81544a6d>] dump_stack+0x4d/0x63
[<ffffffff81069b4c>] warn_slowpath_common+0xa1/0xbb
[<ffffffff811dad37>] ? sysfs_remove_group+0x54/0x88
[<ffffffff81069bac>] warn_slowpath_fmt+0x46/0x48
[<ffffffff811d77ad>] ? kernfs_find_and_get_ns+0x4d/0x58
[<ffffffff811dad37>] sysfs_remove_group+0x54/0x88
[<ffffffff81387835>] dpm_sysfs_remove+0x50/0x55
[<ffffffff8137de7c>] device_del+0x47/0x1ec
[<ffffffff815482f7>] ? mutex_unlock+0x16/0x18
[<ffffffff8137e069>] device_unregister+0x48/0x54
[<ffffffff8128eb82>] bsg_unregister_queue+0x5f/0x86
[<ffffffff813aac83>] __scsi_remove_device+0x3a/0xc3
[<ffffffff813aad32>] scsi_remove_device+0x26/0x33
[<ffffffff813aaea2>] scsi_remove_target+0x134/0x19b
[<ffffffffa0078725>] sas_rphy_remove+0x2c/0x72 [scsi_transport_sas]
[<ffffffffa007877e>] sas_rphy_delete+0x13/0x1f [scsi_transport_sas]
[<ffffffffa008817c>] sas_destruct_devices+0x58/0x79 [libsas]
[<ffffffff8107cca1>] process_one_work+0x19b/0x2d1
[<ffffffff8107d38e>] worker_thread+0x1dd/0x2bb
[<ffffffff8107d1b1>] ? cancel_delayed_work+0x72/0x72
[<ffffffff8108165a>] kthread+0xa5/0xad
[<ffffffff81080000>] ? task_work_add+0xd/0x53
[<ffffffff810815b5>] ? __kthread_parkme+0x61/0x61
[<ffffffff8154a492>] ret_from_fork+0x42/0x70
[<ffffffff810815b5>] ? __kthread_parkme+0x61/0x61

It looks like we don't wait for sas destruct work properly
on tear down path, at least sas_deform_port() calls
sas_unregister_domain_devices() to schedule destruct work
to a workqueue and then calls sas_port_delete() to remove
the related sysfs files concurrently.

Dan tried to fix this with a different way:

but that patch is never applied. I take a better approach
as suggested by Johannes, that is waiting for pending destruct
work to remove child sysfs files and then removing the parent
sysfs files.

Cc: Dan Williams <>
Cc: Johannes Thumshirn <>
Cc: Praveen Murali <>
Cc: "James E.J. Bottomley" <>
Cc: "Martin K. Petersen" <>
Signed-off-by: Cong Wang <>
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);
port->port->rphy = NULL;

void sas_device_set_phy(struct domain_device *dev, struct sas_port *port)
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