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    Subject[PATCH 5.16 0767/1039] scsi: hisi_sas: Prevent parallel FLR and controller reset
    Date
    From: Qi Liu <liuqi115@huawei.com>

    [ Upstream commit 16775db613c2bdea09705dcb876942c0641a1098 ]

    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 .

    Link: https://lore.kernel.org/r/1639579061-179473-7-git-send-email-john.garry@huawei.com
    Signed-off-by: Qi Liu <liuqi115@huawei.com>
    Signed-off-by: John Garry <john.garry@huawei.com>
    Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    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 f206c433de325..8a13bc08d6575 100644
    --- a/drivers/scsi/hisi_sas/hisi_sas_main.c
    +++ b/drivers/scsi/hisi_sas/hisi_sas_main.c
    @@ -1581,7 +1581,6 @@ 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);
    @@ -1606,9 +1605,9 @@ 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);
    }
    @@ -1619,8 +1618,11 @@ 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 0ef6c21bf0811..11a44d9dd9b2d 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);

    --
    2.34.1


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