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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Ilan Peer <ilan.peer@intel.com>,
        Sara Sharon <sara.sharon@intel.com>,
        Luca Coelho <luciano.coelho@intel.com>,
        Sasha Levin <sashal@kernel.org>
Subject: [PATCH 4.14 068/121] iwlwifi: pcie: fix emergency path
Date:   Thu,  4 Apr 2019 10:47:36 +0200
Message-Id: <20190404084548.959197639@linuxfoundation.org>
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4.14-stable review patch.  If anyone has any objections, please let me know.

------------------

[ Upstream commit c6ac9f9fb98851f47b978a9476594fc3c477a34d ]

Allocator swaps the pending requests with 0 when it starts
working. This means that relying on it n RX path to decide if
to move to emergency is not always a good idea, since it may
be zero, but there are still a lot of unallocated RBs in the
system. Change allocator to decrement the pending requests on
real time. It is more expensive since it accesses the atomic
variable more times, but it gives the RX path a better idea
of the system's status.

Reported-by: Ilan Peer <ilan.peer@intel.com>
Signed-off-by: Sara Sharon <sara.sharon@intel.com>
Fixes: 868a1e863f95 ("iwlwifi: pcie: avoid empty free RB queue")
Signed-off-by: Luca Coelho <luciano.coelho@intel.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 drivers/net/wireless/intel/iwlwifi/pcie/rx.c | 11 ++++++++---
 1 file changed, 8 insertions(+), 3 deletions(-)

diff --git a/drivers/net/wireless/intel/iwlwifi/pcie/rx.c b/drivers/net/wireless/intel/iwlwifi/pcie/rx.c
index 5a15362ef671..a40ad4675e19 100644
--- a/drivers/net/wireless/intel/iwlwifi/pcie/rx.c
+++ b/drivers/net/wireless/intel/iwlwifi/pcie/rx.c
@@ -475,7 +475,7 @@ static void iwl_pcie_rx_allocator(struct iwl_trans *trans)
 	struct iwl_trans_pcie *trans_pcie = IWL_TRANS_GET_PCIE_TRANS(trans);
 	struct iwl_rb_allocator *rba = &trans_pcie->rba;
 	struct list_head local_empty;
-	int pending = atomic_xchg(&rba->req_pending, 0);
+	int pending = atomic_read(&rba->req_pending);
 
 	IWL_DEBUG_RX(trans, "Pending allocation requests = %d\n", pending);
 
@@ -530,11 +530,13 @@ static void iwl_pcie_rx_allocator(struct iwl_trans *trans)
 			i++;
 		}
 
+		atomic_dec(&rba->req_pending);
 		pending--;
+
 		if (!pending) {
-			pending = atomic_xchg(&rba->req_pending, 0);
+			pending = atomic_read(&rba->req_pending);
 			IWL_DEBUG_RX(trans,
-				     "Pending allocation requests = %d\n",
+				     "Got more pending allocation requests = %d\n",
 				     pending);
 		}
 
@@ -546,12 +548,15 @@ static void iwl_pcie_rx_allocator(struct iwl_trans *trans)
 		spin_unlock(&rba->lock);
 
 		atomic_inc(&rba->req_ready);
+
 	}
 
 	spin_lock(&rba->lock);
 	/* return unused rbds to the allocator empty list */
 	list_splice_tail(&local_empty, &rba->rbd_empty);
 	spin_unlock(&rba->lock);
+
+	IWL_DEBUG_RX(trans, "%s, exit.\n", __func__);
 }
 
 /*
-- 
2.19.1