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287 lines
8.7 KiB
287 lines
8.7 KiB
From: Dongxiao Xu <dongxiao.xu@intel.com>
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Subject: [PATCH 3/3] Use Kernel thread to replace the tasklet.
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Patch-mainline: n/a
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Kernel thread has more control over QoS, and could improve
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dom0's userspace responseness.
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Signed-off-by: Dongxiao Xu <dongxiao.xu@intel.com>
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Subject: xen: ensure locking gnttab_copy_grant_page is safe against interrupts.
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Now that netback processing occurs in a thread instead of a tasklet
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gnttab_copy_grant_page needs to be safe against interrupts.
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The code is currently commented out in this tree but on 2.6.18 we observed a
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deadlock where the netback thread called gnttab_copy_grant_page, locked
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gnttab_dma_lock for writing, was interrupted and on return from interrupt the
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network stack's TX tasklet ended up calling __gnttab_dma_map_page via the
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hardware driver->swiotlb and tries to take gnttab_dma_lock for reading.
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Signed-off-by: Ian Campbell <ian.campbell@citrix.com>
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Cc: Jeremy Fitzhardinge <jeremy@goop.org>#
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Cc: "Xu, Dongxiao" <dongxiao.xu@intel.com>
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jb: changed write_seq{,un}lock_irq() to write_seq{,un}lock_bh(), and
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made the use of kernel threads optional (but default)
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Acked-by: jbeulich@novell.com
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--- head-2010-04-29.orig/drivers/xen/core/gnttab.c 2010-04-15 11:42:34.000000000 +0200
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+++ head-2010-04-29/drivers/xen/core/gnttab.c 2010-04-15 11:44:26.000000000 +0200
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@@ -554,14 +554,14 @@ int gnttab_copy_grant_page(grant_ref_t r
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mfn = pfn_to_mfn(pfn);
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new_mfn = virt_to_mfn(new_addr);
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- write_seqlock(&gnttab_dma_lock);
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+ write_seqlock_bh(&gnttab_dma_lock);
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/* Make seq visible before checking page_mapped. */
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smp_mb();
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/* Has the page been DMA-mapped? */
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if (unlikely(page_mapped(page))) {
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- write_sequnlock(&gnttab_dma_lock);
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+ write_sequnlock_bh(&gnttab_dma_lock);
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put_page(new_page);
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err = -EBUSY;
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goto out;
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@@ -578,7 +578,7 @@ int gnttab_copy_grant_page(grant_ref_t r
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BUG_ON(err);
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BUG_ON(unmap.status);
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- write_sequnlock(&gnttab_dma_lock);
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+ write_sequnlock_bh(&gnttab_dma_lock);
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if (!xen_feature(XENFEAT_auto_translated_physmap)) {
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set_phys_to_machine(page_to_pfn(new_page), INVALID_P2M_ENTRY);
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--- head-2010-04-29.orig/drivers/xen/netback/common.h 2010-04-30 11:32:08.000000000 +0200
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+++ head-2010-04-29/drivers/xen/netback/common.h 2010-04-30 11:32:26.000000000 +0200
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@@ -239,8 +239,16 @@ struct netbk_tx_pending_inuse {
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#define MAX_MFN_ALLOC 64
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struct xen_netbk {
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- struct tasklet_struct net_tx_tasklet;
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- struct tasklet_struct net_rx_tasklet;
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+ union {
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+ struct {
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+ struct tasklet_struct net_tx_tasklet;
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+ struct tasklet_struct net_rx_tasklet;
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+ };
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+ struct {
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+ wait_queue_head_t netbk_action_wq;
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+ struct task_struct *task;
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+ };
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+ };
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struct sk_buff_head rx_queue;
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struct sk_buff_head tx_queue;
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--- head-2010-04-29.orig/drivers/xen/netback/netback.c 2010-04-30 11:49:27.000000000 +0200
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+++ head-2010-04-29/drivers/xen/netback/netback.c 2010-04-30 11:49:32.000000000 +0200
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@@ -35,6 +35,7 @@
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*/
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#include "common.h"
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+#include <linux/kthread.h>
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#include <linux/vmalloc.h>
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#include <xen/balloon.h>
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#include <xen/interface/memory.h>
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@@ -43,6 +44,8 @@
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struct xen_netbk *__read_mostly xen_netbk;
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unsigned int __read_mostly netbk_nr_groups;
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+static bool __read_mostly use_kthreads = true;
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+static bool __initdata bind_threads;
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#define GET_GROUP_INDEX(netif) ((netif)->group)
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@@ -127,7 +130,11 @@ static int MODPARM_permute_returns = 0;
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module_param_named(permute_returns, MODPARM_permute_returns, bool, S_IRUSR|S_IWUSR);
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MODULE_PARM_DESC(permute_returns, "Randomly permute the order in which TX responses are sent to the frontend");
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module_param_named(groups, netbk_nr_groups, uint, 0);
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-MODULE_PARM_DESC(groups, "Specify the number of tasklet pairs to use");
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+MODULE_PARM_DESC(groups, "Specify the number of tasklet pairs/threads to use");
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+module_param_named(tasklets, use_kthreads, invbool, 0);
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+MODULE_PARM_DESC(tasklets, "Use tasklets instead of kernel threads");
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+module_param_named(bind, bind_threads, bool, 0);
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+MODULE_PARM_DESC(bind, "Bind kernel threads to (v)CPUs");
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int netbk_copy_skb_mode;
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@@ -164,8 +171,12 @@ static inline void maybe_schedule_tx_act
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smp_mb();
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if ((nr_pending_reqs(netbk) < (MAX_PENDING_REQS/2)) &&
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- !list_empty(&netbk->net_schedule_list))
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- tasklet_schedule(&netbk->net_tx_tasklet);
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+ !list_empty(&netbk->net_schedule_list)) {
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+ if (use_kthreads)
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+ wake_up(&netbk->netbk_action_wq);
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+ else
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+ tasklet_schedule(&netbk->net_tx_tasklet);
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+ }
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}
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static struct sk_buff *netbk_copy_skb(struct sk_buff *skb)
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@@ -326,7 +337,10 @@ int netif_be_start_xmit(struct sk_buff *
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netbk = &xen_netbk[GET_GROUP_INDEX(netif)];
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skb_queue_tail(&netbk->rx_queue, skb);
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- tasklet_schedule(&netbk->net_rx_tasklet);
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+ if (use_kthreads)
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+ wake_up(&netbk->netbk_action_wq);
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+ else
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+ tasklet_schedule(&netbk->net_rx_tasklet);
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return NETDEV_TX_OK;
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@@ -779,8 +793,12 @@ static void net_rx_action(unsigned long
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/* More work to do? */
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if (!skb_queue_empty(&netbk->rx_queue) &&
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- !timer_pending(&netbk->net_timer))
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- tasklet_schedule(&netbk->net_rx_tasklet);
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+ !timer_pending(&netbk->net_timer)) {
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+ if (use_kthreads)
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+ wake_up(&netbk->netbk_action_wq);
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+ else
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+ tasklet_schedule(&netbk->net_rx_tasklet);
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+ }
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#if 0
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else
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xen_network_done_notify();
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@@ -789,12 +807,18 @@ static void net_rx_action(unsigned long
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static void net_alarm(unsigned long group)
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{
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- tasklet_schedule(&xen_netbk[group].net_rx_tasklet);
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+ if (use_kthreads)
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+ wake_up(&xen_netbk[group].netbk_action_wq);
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+ else
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+ tasklet_schedule(&xen_netbk[group].net_rx_tasklet);
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}
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static void netbk_tx_pending_timeout(unsigned long group)
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{
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- tasklet_schedule(&xen_netbk[group].net_tx_tasklet);
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+ if (use_kthreads)
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+ wake_up(&xen_netbk[group].netbk_action_wq);
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+ else
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+ tasklet_schedule(&xen_netbk[group].net_tx_tasklet);
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}
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struct net_device_stats *netif_be_get_stats(struct net_device *dev)
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@@ -1506,7 +1530,10 @@ static void net_tx_action(unsigned long
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continue;
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}
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- netif_rx(skb);
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+ if (use_kthreads)
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+ netif_rx_ni(skb);
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+ else
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+ netif_rx(skb);
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netif->dev->last_rx = jiffies;
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}
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@@ -1532,7 +1559,10 @@ static void netif_idx_release(struct xen
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netbk->dealloc_prod++;
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spin_unlock_irqrestore(&netbk->release_lock, flags);
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- tasklet_schedule(&netbk->net_tx_tasklet);
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+ if (use_kthreads)
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+ wake_up(&netbk->netbk_action_wq);
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+ else
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+ tasklet_schedule(&netbk->net_tx_tasklet);
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}
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static void netif_page_release(struct page *page, unsigned int order)
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@@ -1670,6 +1700,46 @@ static struct irqaction netif_be_dbg_act
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};
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#endif
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+static inline int rx_work_todo(struct xen_netbk *netbk)
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+{
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+ return !skb_queue_empty(&netbk->rx_queue);
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+}
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+
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+static inline int tx_work_todo(struct xen_netbk *netbk)
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+{
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+ if (netbk->dealloc_cons != netbk->dealloc_prod)
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+ return 1;
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+
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+ if (nr_pending_reqs(netbk) + MAX_SKB_FRAGS < MAX_PENDING_REQS &&
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+ !list_empty(&netbk->net_schedule_list))
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+ return 1;
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+
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+ return 0;
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+}
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+
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+static int netbk_action_thread(void *index)
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+{
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+ unsigned long group = (unsigned long)index;
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+ struct xen_netbk *netbk = &xen_netbk[group];
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+
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+ while (!kthread_should_stop()) {
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+ wait_event_interruptible(netbk->netbk_action_wq,
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+ rx_work_todo(netbk) ||
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+ tx_work_todo(netbk) ||
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+ kthread_should_stop());
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+ cond_resched();
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+
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+ if (rx_work_todo(netbk))
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+ net_rx_action(group);
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+
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+ if (tx_work_todo(netbk))
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+ net_tx_action(group);
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+ }
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+
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+ return 0;
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+}
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+
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+
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static int __init netback_init(void)
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{
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unsigned int i, group;
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@@ -1697,8 +1767,26 @@ static int __init netback_init(void)
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for (group = 0; group < netbk_nr_groups; group++) {
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struct xen_netbk *netbk = &xen_netbk[group];
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- tasklet_init(&netbk->net_tx_tasklet, net_tx_action, group);
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- tasklet_init(&netbk->net_rx_tasklet, net_rx_action, group);
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+ if (use_kthreads) {
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+ init_waitqueue_head(&netbk->netbk_action_wq);
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+ netbk->task = kthread_create(netbk_action_thread,
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+ (void *)(long)group,
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+ "netback/%u", group);
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+
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+ if (!IS_ERR(netbk->task)) {
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+ if (bind_threads)
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+ kthread_bind(netbk->task, group);
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+ wake_up_process(netbk->task);
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+ } else {
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+ printk(KERN_ALERT
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+ "kthread_create() fails at netback\n");
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+ rc = PTR_ERR(netbk->task);
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+ goto failed_init;
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+ }
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+ } else {
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+ tasklet_init(&netbk->net_tx_tasklet, net_tx_action, group);
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+ tasklet_init(&netbk->net_rx_tasklet, net_rx_action, group);
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+ }
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skb_queue_head_init(&netbk->rx_queue);
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skb_queue_head_init(&netbk->tx_queue);
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@@ -1762,8 +1850,11 @@ failed_init:
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while (group-- > 0) {
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struct xen_netbk *netbk = &xen_netbk[group];
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- free_empty_pages_and_pagevec(netbk->mmap_pages,
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- MAX_PENDING_REQS);
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+ if (use_kthreads && netbk->task && !IS_ERR(netbk->task))
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+ kthread_stop(netbk->task);
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+ if (netbk->mmap_pages)
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+ free_empty_pages_and_pagevec(netbk->mmap_pages,
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+ MAX_PENDING_REQS);
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del_timer(&netbk->tx_pending_timer);
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del_timer(&netbk->net_timer);
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}
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