Date:	Wed, 18 Mar 2015 16:14:02 +0200
From:	Yuval Mintz <Yuval.Mintz@...gic.com>
To:	<davem@...emloft.net>, <netdev@...r.kernel.org>
CC:	Yuval Mintz <Yuval.Mintz@...gic.com>,
	Ariel Elior <Ariel.Elior@...gic.com>
Subject: [PATCH v2 net] bnx2x: Fix statistics locking scheme

Statistics' state-machine in bnx2x driver must be synced with various driver
flows, but its current locking scheme manages to be wasteful [using 2 locks +
additional local variable] and prone to race-conditions at the same time,
as the state-machine and 'action' are being accessed under different locks.

This patch cleans up said logic, leaving us with a single lock for the entire
flow and removing the possible races.

Changes from v1:
	Failure to acquire lock fails flow instead of printing a warning and
	allowing access to the critical section.

Signed-off-by: Yuval Mintz <Yuval.Mintz@...gic.com>
Signed-off-by: Ariel Elior <Ariel.Elior@...gic.com>
---
Hi Dave,

Please consider applying this to 'net'.

Thanks,
Yuval
---
 drivers/net/ethernet/broadcom/bnx2x/bnx2x.h       |   4 +-
 drivers/net/ethernet/broadcom/bnx2x/bnx2x_main.c  |  29 ++--
 drivers/net/ethernet/broadcom/bnx2x/bnx2x_sriov.c |   4 +-
 drivers/net/ethernet/broadcom/bnx2x/bnx2x_stats.c | 164 ++++++++++------------
 drivers/net/ethernet/broadcom/bnx2x/bnx2x_stats.h |   6 +-
 5 files changed, 101 insertions(+), 106 deletions(-)

diff --git a/drivers/net/ethernet/broadcom/bnx2x/bnx2x.h b/drivers/net/ethernet/broadcom/bnx2x/bnx2x.h
index 756053c..6a69dbd 100644
--- a/drivers/net/ethernet/broadcom/bnx2x/bnx2x.h
+++ b/drivers/net/ethernet/broadcom/bnx2x/bnx2x.h
@@ -1811,7 +1811,7 @@ struct bnx2x {
 	int			stats_state;
 
 	/* used for synchronization of concurrent threads statistics handling */
-	spinlock_t		stats_lock;
+	struct semaphore	stats_lock;
 
 	/* used by dmae command loader */
 	struct dmae_command	stats_dmae;
@@ -1935,8 +1935,6 @@ struct bnx2x {
 
 	int fp_array_size;
 	u32 dump_preset_idx;
-	bool					stats_started;
-	struct semaphore			stats_sema;
 
 	u8					phys_port_id[ETH_ALEN];
 
diff --git a/drivers/net/ethernet/broadcom/bnx2x/bnx2x_main.c b/drivers/net/ethernet/broadcom/bnx2x/bnx2x_main.c
index bef750a..8267981 100644
--- a/drivers/net/ethernet/broadcom/bnx2x/bnx2x_main.c
+++ b/drivers/net/ethernet/broadcom/bnx2x/bnx2x_main.c
@@ -12038,8 +12038,7 @@ static int bnx2x_init_bp(struct bnx2x *bp)
 	mutex_init(&bp->fw_mb_mutex);
 	mutex_init(&bp->drv_info_mutex);
 	bp->drv_info_mng_owner = false;
-	spin_lock_init(&bp->stats_lock);
-	sema_init(&bp->stats_sema, 1);
+	sema_init(&bp->stats_lock, 1);
 
 	INIT_DELAYED_WORK(&bp->sp_task, bnx2x_sp_task);
 	INIT_DELAYED_WORK(&bp->sp_rtnl_task, bnx2x_sp_rtnl_task);
@@ -13668,9 +13667,13 @@ static int bnx2x_eeh_nic_unload(struct bnx2x *bp)
 	cancel_delayed_work_sync(&bp->sp_task);
 	cancel_delayed_work_sync(&bp->period_task);
 
-	spin_lock_bh(&bp->stats_lock);
+	 if (down_timeout(&bp->stats_lock, HZ / 10)) {
+		BNX2X_ERR("Unable to acquire stats lock\n");
+		return -EBUSY;
+	}
+
 	bp->stats_state = STATS_STATE_DISABLED;
-	spin_unlock_bh(&bp->stats_lock);
+	up(&bp->stats_lock);
 
 	bnx2x_save_statistics(bp);
 
@@ -13690,6 +13693,7 @@ static int bnx2x_eeh_nic_unload(struct bnx2x *bp)
 static pci_ers_result_t bnx2x_io_error_detected(struct pci_dev *pdev,
 						pci_channel_state_t state)
 {
+	enum pci_ers_result rc = PCI_ERS_RESULT_NEED_RESET;
 	struct net_device *dev = pci_get_drvdata(pdev);
 	struct bnx2x *bp = netdev_priv(dev);
 
@@ -13700,21 +13704,24 @@ static pci_ers_result_t bnx2x_io_error_detected(struct pci_dev *pdev,
 	netif_device_detach(dev);
 
 	if (state == pci_channel_io_perm_failure) {
-		rtnl_unlock();
-		return PCI_ERS_RESULT_DISCONNECT;
+		rc = PCI_ERS_RESULT_DISCONNECT;
+		goto out;
 	}
 
-	if (netif_running(dev))
-		bnx2x_eeh_nic_unload(bp);
+	if (netif_running(dev)) {
+		if (bnx2x_eeh_nic_unload(bp)) {
+			rc = PCI_ERS_RESULT_DISCONNECT;
+			goto out;
+		}
+	}
 
 	bnx2x_prev_path_mark_eeh(bp);
 
 	pci_disable_device(pdev);
 
+out:
 	rtnl_unlock();
-
-	/* Request a slot reset */
-	return PCI_ERS_RESULT_NEED_RESET;
+	return rc;
 }
 
 /**
diff --git a/drivers/net/ethernet/broadcom/bnx2x/bnx2x_sriov.c b/drivers/net/ethernet/broadcom/bnx2x/bnx2x_sriov.c
index e5aca2d..cfe3c769 100644
--- a/drivers/net/ethernet/broadcom/bnx2x/bnx2x_sriov.c
+++ b/drivers/net/ethernet/broadcom/bnx2x/bnx2x_sriov.c
@@ -2238,7 +2238,9 @@ int bnx2x_vf_close(struct bnx2x *bp, struct bnx2x_virtf *vf)
 
 		cookie.vf = vf;
 		cookie.state = VF_ACQUIRED;
-		bnx2x_stats_safe_exec(bp, bnx2x_set_vf_state, &cookie);
+		rc = bnx2x_stats_safe_exec(bp, bnx2x_set_vf_state, &cookie);
+		if (rc)
+			goto op_err;
 	}
 
 	DP(BNX2X_MSG_IOV, "set state to acquired\n");
diff --git a/drivers/net/ethernet/broadcom/bnx2x/bnx2x_stats.c b/drivers/net/ethernet/broadcom/bnx2x/bnx2x_stats.c
index d160829..5fca527 100644
--- a/drivers/net/ethernet/broadcom/bnx2x/bnx2x_stats.c
+++ b/drivers/net/ethernet/broadcom/bnx2x/bnx2x_stats.c
@@ -123,36 +123,28 @@ static void bnx2x_dp_stats(struct bnx2x *bp)
  */
 static void bnx2x_storm_stats_post(struct bnx2x *bp)
 {
-	if (!bp->stats_pending) {
-		int rc;
+	int rc;
 
-		spin_lock_bh(&bp->stats_lock);
-
-		if (bp->stats_pending) {
-			spin_unlock_bh(&bp->stats_lock);
-			return;
-		}
-
-		bp->fw_stats_req->hdr.drv_stats_counter =
-			cpu_to_le16(bp->stats_counter++);
+	if (bp->stats_pending)
+		return;
 
-		DP(BNX2X_MSG_STATS, "Sending statistics ramrod %d\n",
-		   le16_to_cpu(bp->fw_stats_req->hdr.drv_stats_counter));
+	bp->fw_stats_req->hdr.drv_stats_counter =
+		cpu_to_le16(bp->stats_counter++);
 
-		/* adjust the ramrod to include VF queues statistics */
-		bnx2x_iov_adjust_stats_req(bp);
-		bnx2x_dp_stats(bp);
+	DP(BNX2X_MSG_STATS, "Sending statistics ramrod %d\n",
+	   le16_to_cpu(bp->fw_stats_req->hdr.drv_stats_counter));
 
-		/* send FW stats ramrod */
-		rc = bnx2x_sp_post(bp, RAMROD_CMD_ID_COMMON_STAT_QUERY, 0,
-				   U64_HI(bp->fw_stats_req_mapping),
-				   U64_LO(bp->fw_stats_req_mapping),
-				   NONE_CONNECTION_TYPE);
-		if (rc == 0)
-			bp->stats_pending = 1;
+	/* adjust the ramrod to include VF queues statistics */
+	bnx2x_iov_adjust_stats_req(bp);
+	bnx2x_dp_stats(bp);
 
-		spin_unlock_bh(&bp->stats_lock);
-	}
+	/* send FW stats ramrod */
+	rc = bnx2x_sp_post(bp, RAMROD_CMD_ID_COMMON_STAT_QUERY, 0,
+			   U64_HI(bp->fw_stats_req_mapping),
+			   U64_LO(bp->fw_stats_req_mapping),
+			   NONE_CONNECTION_TYPE);
+	if (rc == 0)
+		bp->stats_pending = 1;
 }
 
 static void bnx2x_hw_stats_post(struct bnx2x *bp)
@@ -221,7 +213,7 @@ static void bnx2x_stats_comp(struct bnx2x *bp)
  */
 
 /* should be called under stats_sema */
-static void __bnx2x_stats_pmf_update(struct bnx2x *bp)
+static void bnx2x_stats_pmf_update(struct bnx2x *bp)
 {
 	struct dmae_command *dmae;
 	u32 opcode;
@@ -519,7 +511,7 @@ static void bnx2x_func_stats_init(struct bnx2x *bp)
 }
 
 /* should be called under stats_sema */
-static void __bnx2x_stats_start(struct bnx2x *bp)
+static void bnx2x_stats_start(struct bnx2x *bp)
 {
 	if (IS_PF(bp)) {
 		if (bp->port.pmf)
@@ -531,34 +523,13 @@ static void __bnx2x_stats_start(struct bnx2x *bp)
 		bnx2x_hw_stats_post(bp);
 		bnx2x_storm_stats_post(bp);
 	}
-
-	bp->stats_started = true;
-}
-
-static void bnx2x_stats_start(struct bnx2x *bp)
-{
-	if (down_timeout(&bp->stats_sema, HZ/10))
-		BNX2X_ERR("Unable to acquire stats lock\n");
-	__bnx2x_stats_start(bp);
-	up(&bp->stats_sema);
 }
 
 static void bnx2x_stats_pmf_start(struct bnx2x *bp)
 {
-	if (down_timeout(&bp->stats_sema, HZ/10))
-		BNX2X_ERR("Unable to acquire stats lock\n");
 	bnx2x_stats_comp(bp);
-	__bnx2x_stats_pmf_update(bp);
-	__bnx2x_stats_start(bp);
-	up(&bp->stats_sema);
-}
-
-static void bnx2x_stats_pmf_update(struct bnx2x *bp)
-{
-	if (down_timeout(&bp->stats_sema, HZ/10))
-		BNX2X_ERR("Unable to acquire stats lock\n");
-	__bnx2x_stats_pmf_update(bp);
-	up(&bp->stats_sema);
+	bnx2x_stats_pmf_update(bp);
+	bnx2x_stats_start(bp);
 }
 
 static void bnx2x_stats_restart(struct bnx2x *bp)
@@ -568,11 +539,9 @@ static void bnx2x_stats_restart(struct bnx2x *bp)
 	 */
 	if (IS_VF(bp))
 		return;
-	if (down_timeout(&bp->stats_sema, HZ/10))
-		BNX2X_ERR("Unable to acquire stats lock\n");
+
 	bnx2x_stats_comp(bp);
-	__bnx2x_stats_start(bp);
-	up(&bp->stats_sema);
+	bnx2x_stats_start(bp);
 }
 
 static void bnx2x_bmac_stats_update(struct bnx2x *bp)
@@ -1246,18 +1215,12 @@ static void bnx2x_stats_update(struct bnx2x *bp)
 {
 	u32 *stats_comp = bnx2x_sp(bp, stats_comp);
 
-	/* we run update from timer context, so give up
-	 * if somebody is in the middle of transition
-	 */
-	if (down_trylock(&bp->stats_sema))
+	if (bnx2x_edebug_stats_stopped(bp))
 		return;
 
-	if (bnx2x_edebug_stats_stopped(bp) || !bp->stats_started)
-		goto out;
-
 	if (IS_PF(bp)) {
 		if (*stats_comp != DMAE_COMP_VAL)
-			goto out;
+			return;
 
 		if (bp->port.pmf)
 			bnx2x_hw_stats_update(bp);
@@ -1267,7 +1230,7 @@ static void bnx2x_stats_update(struct bnx2x *bp)
 				BNX2X_ERR("storm stats were not updated for 3 times\n");
 				bnx2x_panic();
 			}
-			goto out;
+			return;
 		}
 	} else {
 		/* vf doesn't collect HW statistics, and doesn't get completions
@@ -1281,7 +1244,7 @@ static void bnx2x_stats_update(struct bnx2x *bp)
 
 	/* vf is done */
 	if (IS_VF(bp))
-		goto out;
+		return;
 
 	if (netif_msg_timer(bp)) {
 		struct bnx2x_eth_stats *estats = &bp->eth_stats;
@@ -1292,9 +1255,6 @@ static void bnx2x_stats_update(struct bnx2x *bp)
 
 	bnx2x_hw_stats_post(bp);
 	bnx2x_storm_stats_post(bp);
-
-out:
-	up(&bp->stats_sema);
 }
 
 static void bnx2x_port_stats_stop(struct bnx2x *bp)
@@ -1358,12 +1318,7 @@ static void bnx2x_port_stats_stop(struct bnx2x *bp)
 
 static void bnx2x_stats_stop(struct bnx2x *bp)
 {
-	int update = 0;
-
-	if (down_timeout(&bp->stats_sema, HZ/10))
-		BNX2X_ERR("Unable to acquire stats lock\n");
-
-	bp->stats_started = false;
+	bool update = false;
 
 	bnx2x_stats_comp(bp);
 
@@ -1381,8 +1336,6 @@ static void bnx2x_stats_stop(struct bnx2x *bp)
 		bnx2x_hw_stats_post(bp);
 		bnx2x_stats_comp(bp);
 	}
-
-	up(&bp->stats_sema);
 }
 
 static void bnx2x_stats_do_nothing(struct bnx2x *bp)
@@ -1410,18 +1363,30 @@ static const struct {
 
 void bnx2x_stats_handle(struct bnx2x *bp, enum bnx2x_stats_event event)
 {
-	enum bnx2x_stats_state state;
-	void (*action)(struct bnx2x *bp);
+	enum bnx2x_stats_state state = bp->stats_state;
+
 	if (unlikely(bp->panic))
 		return;
 
-	spin_lock_bh(&bp->stats_lock);
-	state = bp->stats_state;
+	/* Statistics update run from timer context, and we don't want to stop
+	 * that context in case someone is in the middle of a transition.
+	 * For other events, wait a bit until lock is taken.
+	 */
+	if (down_trylock(&bp->stats_lock)) {
+		if (event == STATS_EVENT_UPDATE)
+			return;
+
+		if (down_timeout(&bp->stats_lock, HZ / 10)) {
+			BNX2X_ERR("Unable to acquire stats lock [Current state %d, event %d]\n",
+				  state, event);
+			return;
+		}
+	}
+
+	bnx2x_stats_stm[state][event].action(bp);
 	bp->stats_state = bnx2x_stats_stm[state][event].next_state;
-	action = bnx2x_stats_stm[state][event].action;
-	spin_unlock_bh(&bp->stats_lock);
 
-	action(bp);
+	up(&bp->stats_lock);
 
 	if ((event != STATS_EVENT_UPDATE) || netif_msg_timer(bp))
 		DP(BNX2X_MSG_STATS, "state %d -> event %d -> state %d\n",
@@ -1998,13 +1963,36 @@ void bnx2x_afex_collect_stats(struct bnx2x *bp, void *void_afex_stats,
 	}
 }
 
-void bnx2x_stats_safe_exec(struct bnx2x *bp,
-			   void (func_to_exec)(void *cookie),
-			   void *cookie){
-	if (down_timeout(&bp->stats_sema, HZ/10))
+int bnx2x_stats_safe_exec(struct bnx2x *bp,
+			  void (func_to_exec)(void *cookie),
+			  void *cookie)
+{
+	int cnt = 10;
+
+	if (down_timeout(&bp->stats_lock, HZ / 10)) {
 		BNX2X_ERR("Unable to acquire stats lock\n");
+		return -EBUSY;
+	}
+
+	/* Wait for statistics to end, then run supplied function 'safely' */
 	bnx2x_stats_comp(bp);
+	while (bp->stats_pending && cnt) {
+		if (bnx2x_storm_stats_update(bp)) {
+			usleep_range(1000, 2000);
+			cnt--;
+		}
+	}
+	if (bp->stats_pending) {
+		BNX2X_ERR("Failed to wait for stats pending to clear\n");
+		return -EBUSY;
+	}
+
 	func_to_exec(cookie);
-	__bnx2x_stats_start(bp);
-	up(&bp->stats_sema);
+
+	/* No need to restart statistics - if they're enabled, the timers
+	 * will restart the statistics.
+	 */
+	up(&bp->stats_lock);
+
+	return 0;
 }
diff --git a/drivers/net/ethernet/broadcom/bnx2x/bnx2x_stats.h b/drivers/net/ethernet/broadcom/bnx2x/bnx2x_stats.h
index 2beceae..965539a 100644
--- a/drivers/net/ethernet/broadcom/bnx2x/bnx2x_stats.h
+++ b/drivers/net/ethernet/broadcom/bnx2x/bnx2x_stats.h
@@ -539,9 +539,9 @@ struct bnx2x;
 void bnx2x_memset_stats(struct bnx2x *bp);
 void bnx2x_stats_init(struct bnx2x *bp);
 void bnx2x_stats_handle(struct bnx2x *bp, enum bnx2x_stats_event event);
-void bnx2x_stats_safe_exec(struct bnx2x *bp,
-			   void (func_to_exec)(void *cookie),
-			   void *cookie);
+int bnx2x_stats_safe_exec(struct bnx2x *bp,
+			  void (func_to_exec)(void *cookie),
+			  void *cookie);
 
 /**
  * bnx2x_save_statistics - save statistics when unloading.
-- 
1.9.3

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