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    Subject[PATCH 2/2] [SCSI] pm8001: Fix possible racing codition.
    Date
    From: Santosh Nayak <santoshprasadnayak@gmail.com>

    There is a possble racing scenario.

    'process_oq' is called by two routines, as shown below.

    pm8001_8001_dispatch = {
    .......

    .isr = pm8001_chip_isr --> process_oq,// A
    .isr_process_oq = process_oq, // B
    .....
    }

    process_oq() --> process_one_iomb() --> mpi_sata_completion()

    In 'mpi_sata_completion', "pm8001_ha->lock" is first released.
    It means lock is taken before, which is true for
    the context A, as 'pm8001_ha->lock' is taken in 'pm8001_chip_isr()'

    But for context B there is no lock taken before and pm8001_ha->lock
    is unlocked in 'mpi_sata_completion()'. This may unlock the lock
    taken in context A. Possible racing ??

    If 'pm8001_ha->lock' is taken in 'process_oq()' instead of
    'pm8001_chip_isr' then the above issue can be avoided.

    Signed-off-by: Santosh Nayak <santoshprasadnayak@gmail.com>
    ---
    drivers/scsi/pm8001/pm8001_hwi.c | 6 +++---
    1 files changed, 3 insertions(+), 3 deletions(-)

    diff --git a/drivers/scsi/pm8001/pm8001_hwi.c b/drivers/scsi/pm8001/pm8001_hwi.c
    index 838e3e2..6d9973b 100644
    --- a/drivers/scsi/pm8001/pm8001_hwi.c
    +++ b/drivers/scsi/pm8001/pm8001_hwi.c
    @@ -3663,7 +3663,9 @@ static int process_oq(struct pm8001_hba_info *pm8001_ha)
    void *pMsg1 = NULL;
    u8 uninitialized_var(bc);
    u32 ret = MPI_IO_STATUS_FAIL;
    + unsigned long flags;

    + spin_lock_irqsave(&pm8001_ha->lock, flags);
    circularQ = &pm8001_ha->outbnd_q_tbl[0];
    do {
    ret = mpi_msg_consume(pm8001_ha, circularQ, &pMsg1, &bc);
    @@ -3682,6 +3684,7 @@ static int process_oq(struct pm8001_hba_info *pm8001_ha)
    break;
    }
    } while (1);
    + spin_unlock_irqrestore(&pm8001_ha->lock, flags);
    return ret;
    }

    @@ -4087,12 +4090,9 @@ static u32 pm8001_chip_is_our_interupt(struct pm8001_hba_info *pm8001_ha)
    static irqreturn_t
    pm8001_chip_isr(struct pm8001_hba_info *pm8001_ha)
    {
    - unsigned long flags;
    - spin_lock_irqsave(&pm8001_ha->lock, flags);
    pm8001_chip_interrupt_disable(pm8001_ha);
    process_oq(pm8001_ha);
    pm8001_chip_interrupt_enable(pm8001_ha);
    - spin_unlock_irqrestore(&pm8001_ha->lock, flags);
    return IRQ_HANDLED;
    }

    --
    1.7.4.4


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