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    Subject[PATCH] scsi: bnx2fc: make bnx2fc_recv_frame mp safe
    Date
        Running tests with a debug kernel shows that bnx2fc_recv_frame is
    modifying the per_cpu lport stats counters in a non-mpsafe way.
    Just boot a debug kernel and run the bnx2fc driver with the hardware
    enabled.

    [ 1391.699147] BUG: using smp_processor_id() in preemptible [00000000] code: bnx2fc_
    [ 1391.699160] caller is bnx2fc_recv_frame+0xbf9/0x1760 [bnx2fc]
    [ 1391.699174] CPU: 2 PID: 4355 Comm: bnx2fc_l2_threa Kdump: loaded Tainted: G B
    [ 1391.699180] Hardware name: HP ProLiant DL120 G7, BIOS J01 07/01/2013
    [ 1391.699183] Call Trace:
    [ 1391.699188] dump_stack_lvl+0x57/0x7d
    [ 1391.699198] check_preemption_disabled+0xc8/0xd0
    [ 1391.699205] bnx2fc_recv_frame+0xbf9/0x1760 [bnx2fc]
    [ 1391.699215] ? do_raw_spin_trylock+0xb5/0x180
    [ 1391.699221] ? bnx2fc_npiv_create_vports.isra.0+0x4e0/0x4e0 [bnx2fc]
    [ 1391.699229] ? bnx2fc_l2_rcv_thread+0xb7/0x3a0 [bnx2fc]
    [ 1391.699240] bnx2fc_l2_rcv_thread+0x1af/0x3a0 [bnx2fc]
    [ 1391.699250] ? bnx2fc_ulp_init+0xc0/0xc0 [bnx2fc]
    [ 1391.699258] kthread+0x364/0x420
    [ 1391.699263] ? _raw_spin_unlock_irq+0x24/0x50
    [ 1391.699268] ? set_kthread_struct+0x100/0x100
    [ 1391.699273] ret_from_fork+0x22/0x30

    To fix the problem: restore the old get_cpu/put_cpu code with some
    modifications to reduce the size of the critical section.

    Fixes: d576a5e80cd0 ("bnx2fc: Improve stats update mechanism")
    Tested-by: Guangwu Zhang <guazhang@redhat.com>
    Signed-off-by: John Meneghini <jmeneghi@redhat.com>
    ---
    drivers/scsi/bnx2fc/bnx2fc_fcoe.c | 21 +++++++++++++--------
    1 file changed, 13 insertions(+), 8 deletions(-)

    diff --git a/drivers/scsi/bnx2fc/bnx2fc_fcoe.c b/drivers/scsi/bnx2fc/bnx2fc_fcoe.c
    index 71fa62bd3083..e41a94dc2d1f 100644
    --- a/drivers/scsi/bnx2fc/bnx2fc_fcoe.c
    +++ b/drivers/scsi/bnx2fc/bnx2fc_fcoe.c
    @@ -508,7 +508,8 @@ static int bnx2fc_l2_rcv_thread(void *arg)

    static void bnx2fc_recv_frame(struct sk_buff *skb)
    {
    - u32 fr_len;
    + u64 crc_err;
    + u32 fr_len, fr_crc;
    struct fc_lport *lport;
    struct fcoe_rcv_info *fr;
    struct fc_stats *stats;
    @@ -542,6 +543,11 @@ static void bnx2fc_recv_frame(struct sk_buff *skb)
    skb_pull(skb, sizeof(struct fcoe_hdr));
    fr_len = skb->len - sizeof(struct fcoe_crc_eof);

    + stats = per_cpu_ptr(lport->stats, get_cpu());
    + stats->RxFrames++;
    + stats->RxWords += fr_len / FCOE_WORD_TO_BYTE;
    + put_cpu();
    +
    fp = (struct fc_frame *)skb;
    fc_frame_init(fp);
    fr_dev(fp) = lport;
    @@ -624,16 +630,15 @@ static void bnx2fc_recv_frame(struct sk_buff *skb)
    return;
    }

    - stats = per_cpu_ptr(lport->stats, smp_processor_id());
    - stats->RxFrames++;
    - stats->RxWords += fr_len / FCOE_WORD_TO_BYTE;
    + fr_crc = le32_to_cpu(fr_crc(fp));

    - if (le32_to_cpu(fr_crc(fp)) !=
    - ~crc32(~0, skb->data, fr_len)) {
    - if (stats->InvalidCRCCount < 5)
    + if (unlikely(fr_crc != ~crc32(~0, skb->data, fr_len))) {
    + stats = per_cpu_ptr(lport->stats, get_cpu());
    + crc_err = (stats->InvalidCRCCount++);
    + put_cpu();
    + if (crc_err < 5)
    printk(KERN_WARNING PFX "dropping frame with "
    "CRC error\n");
    - stats->InvalidCRCCount++;
    kfree_skb(skb);
    return;
    }
    --
    2.27.0
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