From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Date: Fri, 6 May 2022 12:57:58 +0200
Subject: [PATCH 4/4] scsi: bnx2fc: Avoid using get_cpu() in
 bnx2fc_cmd_alloc().

Using get_cpu() leads to disabling preemption and in this context it is
not possible to acquire the following spinlock_t on PREEMPT_RT because
it becomes a sleeping lock.

Commit
   0ea5c27583e1c ("[SCSI] bnx2fc: common free list for cleanup commands")

says that it is using get_cpu() as a fix in case the CPU is preempted.
While this might be true, the important part is that it is now using the
same CPU for locking and unlocking while previously it always relied on
smp_processor_id().
The date structure itself is protected with a lock so it does not rely
on CPU-local access.

Replace get_cpu() with raw_smp_processor_id() to obtain the current CPU
number which is used as an index for the per-CPU resource.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Link: https://lore.kernel.org/r/20220506105758.283887-5-bigeasy@linutronix.de
---
 drivers/scsi/bnx2fc/bnx2fc_io.c |    4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

--- a/drivers/scsi/bnx2fc/bnx2fc_io.c
+++ b/drivers/scsi/bnx2fc/bnx2fc_io.c
@@ -472,7 +472,7 @@ struct bnx2fc_cmd *bnx2fc_cmd_alloc(stru
 	u32 free_sqes;
 	u32 max_sqes;
 	u16 xid;
-	int index = get_cpu();
+	int index = raw_smp_processor_id();
 
 	max_sqes = BNX2FC_SCSI_MAX_SQES;
 	/*
@@ -485,7 +485,6 @@ struct bnx2fc_cmd *bnx2fc_cmd_alloc(stru
 	    (tgt->num_active_ios.counter  >= max_sqes) ||
 	    (free_sqes + max_sqes <= BNX2FC_SQ_WQES_MAX)) {
 		spin_unlock_bh(&cmd_mgr->free_list_lock[index]);
-		put_cpu();
 		return NULL;
 	}
 
@@ -498,7 +497,6 @@ struct bnx2fc_cmd *bnx2fc_cmd_alloc(stru
 	atomic_inc(&tgt->num_active_ios);
 	atomic_dec(&tgt->free_sqes);
 	spin_unlock_bh(&cmd_mgr->free_list_lock[index]);
-	put_cpu();
 
 	INIT_LIST_HEAD(&io_req->link);