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Commit 19e94bbc authored by Subash Abhinov Kasiviswanathan's avatar Subash Abhinov Kasiviswanathan
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net: rmnet_data: Remove the NAPI context for rmnet_data devices 



Commit 28207b51 ("net: rmnet_data: Add NAPI context for rmnet_data
devices") added a NAPI struct per rmnet_data device. This was to
ensure that the NAPI struct is always available even if there was a
hotplug. However, this seems to be leading to some races where the
NAPI struct is accessed concurrently across cores.

The race here is between napi_gro_receive on one core with
napi_complete running on the other accessing the same NAPI struct.
If napi_gro_receive runs slightly earlier, napi_complete would see
that the napi->gro_list would be non NULL in __napi_complete even
though it had cleared earlier and would lead to a BUG.
If napi_complete runs slightly earlier, napi_gro_receive would
dereference a NULL pointer even though it had assigned an skb to
napi->gro_list.

Fix this by using the per cpu backlog struct as the NAPI struct for
queuing packets to GRO engine. Access across cores would not be a
problem in case of hotplug as they would use core specific structures.

CRs-Fixed: 966095
Change-Id: I831df5b93cc6ee77355f2e98af89efcffe825bd8
Signed-off-by: default avatarSubash Abhinov Kasiviswanathan <subashab@codeaurora.org>
parent d1701bc2

net/rmnet_data/rmnet_data_handlers.c

+6 −6
Original line number Diff line number Diff line 
/*

 * Copyright (c) 2013-2015, The Linux Foundation. All rights reserved.

 * Copyright (c) 2013-2016, The Linux Foundation. All rights reserved.

 *

 * This program is free software; you can redistribute it and/or modify

 * it under the terms of the GNU General Public License version 2 and
@@ -250,14 +250,14 @@ static rx_handler_result_t __rmnet_deliver_skb(struct sk_buff *skb, 
		case RX_HANDLER_PASS:

			skb->pkt_type = PACKET_HOST;

			rmnet_reset_mac_header(skb);



			if (rmnet_check_skb_can_gro(skb)) {

				if (skb->dev->features & NETIF_F_GRO) {

					napi = rmnet_vnd_get_napi(skb->dev);

					napi_schedule(napi);

			if (rmnet_check_skb_can_gro(skb) &&

			    (skb->dev->features & NETIF_F_GRO)) {

				napi = get_current_napi_context();

				if (napi != NULL) {

					gro_res = napi_gro_receive(napi, skb);

					trace_rmnet_gro_downlink(gro_res);

				} else {

					WARN_ONCE(1, "current napi is NULL\n");

					netif_receive_skb(skb);

				}

			} else {

net/rmnet_data/rmnet_data_vnd.c

+2 −40
Original line number Diff line number Diff line 
/*

 * Copyright (c) 2013-2015, The Linux Foundation. All rights reserved.

 * Copyright (c) 2013-2016, The Linux Foundation. All rights reserved.

 *

 * This program is free software; you can redistribute it and/or modify

 * it under the terms of the GNU General Public License version 2 and
@@ -19,7 +19,6 @@ 
#include <linux/rmnet_data.h>

#include <linux/msm_rmnet.h>

#include <linux/etherdevice.h>

#include <linux/netdevice.h>

#include <linux/if_arp.h>

#include <linux/spinlock.h>

#include <net/pkt_sched.h>
@@ -38,9 +37,6 @@ RMNET_LOG_MODULE(RMNET_DATA_LOGMASK_VND); 
#define RMNET_MAP_FLOW_NUM_TC_HANDLE 3

#define RMNET_VND_UF_ACTION_ADD 0

#define RMNET_VND_UF_ACTION_DEL 1

#define RMNET_DATA_NAPI_WEIGHT 1

#define RMNET_DATA_NAPI_WORK 0



enum {

	RMNET_VND_UPDATE_FLOW_OK,

	RMNET_VND_UPDATE_FLOW_NO_ACTION,
@@ -62,7 +58,7 @@ struct rmnet_map_flow_mapping_s { 
struct rmnet_vnd_private_s {

	uint32_t qos_version;

	struct rmnet_logical_ep_conf_s local_ep;

	struct napi_struct napi;



	rwlock_t flow_map_lock;

	struct list_head flow_head;

	struct rmnet_map_flow_mapping_s root_flow;
@@ -507,19 +503,6 @@ static void rmnet_vnd_setup(struct net_device *dev) 
	INIT_LIST_HEAD(&dev_conf->flow_head);

}



/**

 * rmnet_data_napi_poll() - NAPI poll function

 * @napi:      NAPI struct

 *

 * Called by net_rx_action() when NAPI is scheduled. Since we have already

 * queued packets to network stack, we just flush and return here.

 */

static int rmnet_data_napi_poll(struct napi_struct *napi, int budget)

{

	napi_complete(napi);

	return RMNET_DATA_NAPI_WORK;

}



/* ***************** Exposed API ******************************************** */



/**
@@ -574,7 +557,6 @@ int rmnet_vnd_create_dev(int id, struct net_device **new_device, 
	struct net_device *dev;

	char dev_prefix[IFNAMSIZ];

	int p, rc = 0;

	struct napi_struct *n;



	if (id < 0 || id >= RMNET_DATA_MAX_VND) {

		*new_device = 0;
@@ -634,10 +616,6 @@ int rmnet_vnd_create_dev(int id, struct net_device **new_device, 
		*new_device = dev;

	}



	n = rmnet_vnd_get_napi(dev);

	netif_napi_add(dev, n, rmnet_data_napi_poll, RMNET_DATA_NAPI_WEIGHT);

	napi_enable(n);



	LOGM("Registered device %s", dev->name);

	return rc;

}
@@ -681,10 +659,6 @@ int rmnet_vnd_free_dev(int id) 
	rtnl_unlock();



	if (dev) {

		struct napi_struct *n = rmnet_vnd_get_napi(dev);



		napi_disable(n);

		netif_napi_del(n);

		unregister_netdev(dev);

		free_netdev(dev);

		return 0;
@@ -1125,15 +1099,3 @@ struct net_device *rmnet_vnd_get_by_id(int id) 
	}

	return rmnet_devices[id];

}
 


/**

 * rmnet_vnd_get_napi() - Get NAPI struct from the device

 * @dev: Virtual network device

 *

 * Return:

 *      - napi struct corresponding to the netdevice

 */

struct napi_struct *rmnet_vnd_get_napi(struct net_device *dev)

{

	return &(((struct rmnet_vnd_private_s *)netdev_priv(dev))->napi);

}

net/rmnet_data/rmnet_data_vnd.h

+1 −2
Original line number Diff line number Diff line 
/*

 * Copyright (c) 2013-2015, The Linux Foundation. All rights reserved.

 * Copyright (c) 2013-2016, The Linux Foundation. All rights reserved.

 *

 * This program is free software; you can redistribute it and/or modify

 * it under the terms of the GNU General Public License version 2 and
@@ -37,6 +37,5 @@ int rmnet_vnd_del_tc_flow(uint32_t id, uint32_t map_flow, uint32_t tc_flow); 
int rmnet_vnd_init(void);

void rmnet_vnd_exit(void);

struct net_device *rmnet_vnd_get_by_id(int id);

struct napi_struct *rmnet_vnd_get_napi(struct net_device *dev);



#endif /* _RMNET_DATA_VND_H_ */