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Subject[PATCH 6/8] scsi: hisi_sas: Prevent parallel FLR and controller reset
Date
From: Qi Liu <liuqi115@huawei.com>

If we issue a controller reset command during executing a FLR a hung task
may be found:

Call trace:
__switch_to+0x158/0x1cc
__schedule+0x2e8/0x85c
schedule+0x7c/0x110
schedule_timeout+0x190/0x1cc
__down+0x7c/0xd4
down+0x5c/0x7c
hisi_sas_task_exec+0x510/0x680 [hisi_sas_main]
hisi_sas_queue_command+0x24/0x30 [hisi_sas_main]
smp_execute_task_sg+0xf4/0x23c [libsas]
sas_smp_phy_control+0x110/0x1e0 [libsas]
transport_sas_phy_reset+0xc8/0x190 [libsas]
phy_reset_work+0x2c/0x40 [libsas]
process_one_work+0x1dc/0x48c
worker_thread+0x15c/0x464
kthread+0x160/0x170
ret_from_fork+0x10/0x18

This is a race condition which occurs when the FLR completes first.

Here the host HISI_SAS_RESETTING_BIT flag out gets of sync as
HISI_SAS_RESETTING_BIT is not always cleared with the hisi_hba.sem held,
so now only set/unset HISI_SAS_RESETTING_BIT under hisi_hba.sem .

Signed-off-by: Qi Liu <liuqi115@huawei.com>
Signed-off-by: John Garry <john.garry@huawei.com>
---
drivers/scsi/hisi_sas/hisi_sas_main.c | 8 +++++---
drivers/scsi/hisi_sas/hisi_sas_v3_hw.c | 1 +
2 files changed, 6 insertions(+), 3 deletions(-)

diff --git a/drivers/scsi/hisi_sas/hisi_sas_main.c b/drivers/scsi/hisi_sas/hisi_sas_main.c
index 977911580d8f..0e14f90dbb1e 100644
--- a/drivers/scsi/hisi_sas/hisi_sas_main.c
+++ b/drivers/scsi/hisi_sas/hisi_sas_main.c
@@ -1574,7 +1574,6 @@ void hisi_sas_controller_reset_prepare(struct hisi_hba *hisi_hba)
{
struct Scsi_Host *shost = hisi_hba->shost;

- down(&hisi_hba->sem);
hisi_hba->phy_state = hisi_hba->hw->get_phys_state(hisi_hba);

scsi_block_requests(shost);
@@ -1599,9 +1598,9 @@ void hisi_sas_controller_reset_done(struct hisi_hba *hisi_hba)
if (hisi_hba->reject_stp_links_msk)
hisi_sas_terminate_stp_reject(hisi_hba);
hisi_sas_reset_init_all_devices(hisi_hba);
- up(&hisi_hba->sem);
scsi_unblock_requests(shost);
clear_bit(HISI_SAS_RESETTING_BIT, &hisi_hba->flags);
+ up(&hisi_hba->sem);

hisi_sas_rescan_topology(hisi_hba, hisi_hba->phy_state);
}
@@ -1612,8 +1611,11 @@ static int hisi_sas_controller_prereset(struct hisi_hba *hisi_hba)
if (!hisi_hba->hw->soft_reset)
return -1;

- if (test_and_set_bit(HISI_SAS_RESETTING_BIT, &hisi_hba->flags))
+ down(&hisi_hba->sem);
+ if (test_and_set_bit(HISI_SAS_RESETTING_BIT, &hisi_hba->flags)) {
+ up(&hisi_hba->sem);
return -1;
+ }

if (hisi_sas_debugfs_enable && hisi_hba->debugfs_itct[0].itct)
hisi_hba->hw->debugfs_snapshot_regs(hisi_hba);
diff --git a/drivers/scsi/hisi_sas/hisi_sas_v3_hw.c b/drivers/scsi/hisi_sas/hisi_sas_v3_hw.c
index 0ef6c21bf081..11a44d9dd9b2 100644
--- a/drivers/scsi/hisi_sas/hisi_sas_v3_hw.c
+++ b/drivers/scsi/hisi_sas/hisi_sas_v3_hw.c
@@ -4848,6 +4848,7 @@ static void hisi_sas_reset_prepare_v3_hw(struct pci_dev *pdev)
int rc;

dev_info(dev, "FLR prepare\n");
+ down(&hisi_hba->sem);
set_bit(HISI_SAS_RESETTING_BIT, &hisi_hba->flags);
hisi_sas_controller_reset_prepare(hisi_hba);

--
2.26.2
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