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Revision 6e474083f3daf3a3546737f5d7d502ad12eb257c authored by Wei Xu on 01 December 2017, 10:10:36 UTC, committed by David S. Miller on 03 December 2017, 02:31:03 UTC 
vhost: fix skb leak in handle_rx()
 
Matthew found a roughly 40% tcp throughput regression with commit
c67df11f(vhost_net: try batch dequing from skb array) as discussed
in the following thread:
https://www.mail-archive.com/netdev@vger.kernel.org/msg187936.html

Eventually we figured out that it was a skb leak in handle_rx()
when sending packets to the VM. This usually happens when a guest
can not drain out vq as fast as vhost fills in, afterwards it sets
off the traffic jam and leaks skb(s) which occurs as no headcount
to send on the vq from vhost side.

This can be avoided by making sure we have got enough headcount
before actually consuming a skb from the batched rx array while
transmitting, which is simply done by moving checking the zero
headcount a bit ahead.

Signed-off-by: Wei Xu <wexu@redhat.com>
Reported-by: Matthew Rosato <mjrosato@linux.vnet.ibm.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
1 parent fa935ca
Raw File
sa1100_shannon.c 
// SPDX-License-Identifier: GPL-2.0
/*
 * drivers/pcmcia/sa1100_shannon.c
 *
 * PCMCIA implementation routines for Shannon
 *
 */
#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/device.h>
#include <linux/init.h>
#include <linux/io.h>

#include <mach/hardware.h>
#include <asm/mach-types.h>
#include <mach/shannon.h>
#include <asm/irq.h>
#include "sa1100_generic.h"

static int shannon_pcmcia_hw_init(struct soc_pcmcia_socket *skt)
{
	/* All those are inputs */
	GAFR &= ~(GPIO_GPIO(SHANNON_GPIO_EJECT_0) |
		  GPIO_GPIO(SHANNON_GPIO_EJECT_1) |
		  GPIO_GPIO(SHANNON_GPIO_RDY_0) |
		  GPIO_GPIO(SHANNON_GPIO_RDY_1));

	if (skt->nr == 0) {
		skt->stat[SOC_STAT_CD].gpio = SHANNON_GPIO_EJECT_0;
		skt->stat[SOC_STAT_CD].name = "PCMCIA_CD_0";
		skt->stat[SOC_STAT_RDY].gpio = SHANNON_GPIO_RDY_0;
		skt->stat[SOC_STAT_RDY].name = "PCMCIA_RDY_0";
	} else {
		skt->stat[SOC_STAT_CD].gpio = SHANNON_GPIO_EJECT_1;
		skt->stat[SOC_STAT_CD].name = "PCMCIA_CD_1";
		skt->stat[SOC_STAT_RDY].gpio = SHANNON_GPIO_RDY_1;
		skt->stat[SOC_STAT_RDY].name = "PCMCIA_RDY_1";
	}

	return 0;
}

static void
shannon_pcmcia_socket_state(struct soc_pcmcia_socket *skt,
			    struct pcmcia_state *state)
{
	switch (skt->nr) {
	case 0:
		state->bvd1   = 1; 
		state->bvd2   = 1; 
		state->vs_3v  = 1; /* FIXME Can only apply 3.3V on Shannon. */
		state->vs_Xv  = 0;
		break;

	case 1:
		state->bvd1   = 1; 
		state->bvd2   = 1; 
		state->vs_3v  = 1; /* FIXME Can only apply 3.3V on Shannon. */
		state->vs_Xv  = 0;
		break;
	}
}

static int
shannon_pcmcia_configure_socket(struct soc_pcmcia_socket *skt,
				const socket_state_t *state)
{
	switch (state->Vcc) {
	case 0:	/* power off */
		printk(KERN_WARNING "%s(): CS asked for 0V, still applying 3.3V..\n", __func__);
		break;
	case 50:
		printk(KERN_WARNING "%s(): CS asked for 5V, applying 3.3V..\n", __func__);
	case 33:
		break;
	default:
		printk(KERN_ERR "%s(): unrecognized Vcc %u\n",
		       __func__, state->Vcc);
		return -1;
	}

	printk(KERN_WARNING "%s(): Warning, Can't perform reset\n", __func__);
	
	/* Silently ignore Vpp, output enable, speaker enable. */

	return 0;
}

static struct pcmcia_low_level shannon_pcmcia_ops = {
	.owner			= THIS_MODULE,
	.hw_init		= shannon_pcmcia_hw_init,
	.socket_state		= shannon_pcmcia_socket_state,
	.configure_socket	= shannon_pcmcia_configure_socket,
};

int pcmcia_shannon_init(struct device *dev)
{
	int ret = -ENODEV;

	if (machine_is_shannon())
		ret = sa11xx_drv_pcmcia_probe(dev, &shannon_pcmcia_ops, 0, 2);

	return ret;
}
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