scsi: lpfc: Fix hard lockup when reading the rx_monitor from debugfs

During I/O and simultaneous cat of /sys/kernel/debug/lpfc/fnX/rx_monitor, a
hard lockup similar to the call trace below may occur.

The spin_lock_bh in lpfc_rx_monitor_report is not protecting from timer
interrupts as expected, so change the strength of the spin lock to _irq.

Kernel panic - not syncing: Hard LOCKUP
CPU: 3 PID: 110402 Comm: cat Kdump: loaded

exception RIP: native_queued_spin_lock_slowpath+91

[IRQ stack]
 native_queued_spin_lock_slowpath at ffffffffb814e30b
 _raw_spin_lock at ffffffffb89a667a
 lpfc_rx_monitor_record at ffffffffc0a73a36 [lpfc]
 lpfc_cmf_timer at ffffffffc0abbc67 [lpfc]
 __hrtimer_run_queues at ffffffffb8184250
 hrtimer_interrupt at ffffffffb8184ab0
 smp_apic_timer_interrupt at ffffffffb8a026ba
 apic_timer_interrupt at ffffffffb8a01c4f
[End of IRQ stack]

 apic_timer_interrupt at ffffffffb8a01c4f
 lpfc_rx_monitor_report at ffffffffc0a73c80 [lpfc]
 lpfc_rx_monitor_read at ffffffffc0addde1 [lpfc]
 full_proxy_read at ffffffffb83e7fc3
 vfs_read at ffffffffb833fe71
 ksys_read at ffffffffb83402af
 do_syscall_64 at ffffffffb800430b
 entry_SYSCALL_64_after_hwframe at ffffffffb8a000ad

Signed-off-by: Justin Tee <justin.tee@broadcom.com>
Link: https://lore.kernel.org/r/20221017164323.14536-2-justintee8345@gmail.com
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

diff --git a/drivers/scsi/lpfc/lpfc_sli.c b/drivers/scsi/lpfc/lpfc_sli.c
index 768294b9bc0b0115583703d858b64ef2c474afb0..86ba45ac91c828b7833b5b4e4e26c29de140f29e 100644 (file)
--- a/drivers/scsi/lpfc/lpfc_sli.c
+++ b/drivers/scsi/lpfc/lpfc_sli.c
@@ -8150,10 +8150,10 @@ u32 lpfc_rx_monitor_report(struct lpfc_hba *phba,
                                        "IO_cnt", "Info", "BWutil(ms)");
        }
 
-       /* Needs to be _bh because record is called from timer interrupt
+       /* Needs to be _irq because record is called from timer interrupt
         * context
         */
-       spin_lock_bh(ring_lock);
+       spin_lock_irq(ring_lock);
        while (*head_idx != *tail_idx) {
                entry = &ring[*head_idx];
 
@@ -8197,7 +8197,7 @@ u32 lpfc_rx_monitor_report(struct lpfc_hba *phba,
                if (cnt >= max_read_entries)
                        break;
        }
-       spin_unlock_bh(ring_lock);
+       spin_unlock_irq(ring_lock);
 
        return cnt;
 }