linux-kernel - [PATCH AUTOSEL 5.0 145/262] iwlwifi: pcie: fix emergency path

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Message-Id: <20190327180158.10245-145-sashal@kernel.org>
Date:   Wed, 27 Mar 2019 14:00:00 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Sara Sharon <sara.sharon@...el.com>,
        Luca Coelho <luciano.coelho@...el.com>,
        Sasha Levin <sashal@...nel.org>,
        linux-wireless@...r.kernel.org, netdev@...r.kernel.org
Subject: [PATCH AUTOSEL 5.0 145/262] iwlwifi: pcie: fix emergency path

From: Sara Sharon <sara.sharon@...el.com>

[ 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@...el.com>
Signed-off-by: Sara Sharon <sara.sharon@...el.com>
Fixes: 868a1e863f95 ("iwlwifi: pcie: avoid empty free RB queue")
Signed-off-by: Luca Coelho <luciano.coelho@...el.com>
Signed-off-by: Sasha Levin <sashal@...nel.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 9e850c25877b..c596c7b13504 100644
--- a/drivers/net/wireless/intel/iwlwifi/pcie/rx.c
+++ b/drivers/net/wireless/intel/iwlwifi/pcie/rx.c
@@ -499,7 +499,7 @@ 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);
 
@@ -554,11 +554,13 @@ 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);
 		}
 
@@ -570,12 +572,15 @@ 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