Re: [RFC] Net vm deadlock fix (take two)
From: Jeff Garzik <hidden>
Date: 2005-08-06 16:07:18
On Sat, Aug 06, 2005 at 05:22:23PM +1000, Daniel Phillips wrote:
quoted hunk ↗ jump to hunk
Daniel diff -up --recursive 2.6.12.3.clean/include/linux/gfp.h 2.6.12.3/include/linux/gfp.h--- 2.6.12.3.clean/include/linux/gfp.h 2005-07-15 17:18:57.000000000 -0400 +++ 2.6.12.3/include/linux/gfp.h 2005-08-05 21:53:09.000000000 -0400@@ -39,6 +39,7 @@ struct vm_area_struct; #define __GFP_COMP 0x4000u /* Add compound page metadata */ #define __GFP_ZERO 0x8000u /* Return zeroed page on success */ #define __GFP_NOMEMALLOC 0x10000u /* Don't use emergency reserves */ +#define __GFP_MEMALLOC 0x20000u /* Use emergency reserves */ #define __GFP_BITS_SHIFT 20 /* Room for 20 __GFP_FOO bits */ #define __GFP_BITS_MASK ((1 << __GFP_BITS_SHIFT) - 1)diff -up --recursive 2.6.12.3.clean/include/linux/netdevice.h 2.6.12.3/include/linux/netdevice.h--- 2.6.12.3.clean/include/linux/netdevice.h 2005-07-15 17:18:57.000000000 -0400 +++ 2.6.12.3/include/linux/netdevice.h 2005-08-06 01:06:18.000000000 -0400@@ -371,6 +371,8 @@ struct net_device struct Qdisc *qdisc_ingress; struct list_head qdisc_list; unsigned long tx_queue_len; /* Max frames per queue allowed */ + int rx_reserve; + int rx_reserve_used; /* ingress path synchronizer */ spinlock_t ingress_lock;@@ -929,6 +931,28 @@ extern void net_disable_timestamp(void) extern char *net_sysctl_strdup(const char *s); #endif +static inline struct sk_buff *__dev_memalloc_skb(struct net_device *dev, + unsigned length, int gfp_mask) +{ + struct sk_buff *skb = __dev_alloc_skb(length, gfp_mask); + if (skb) + goto done; + if (dev->rx_reserve_used >= dev->rx_reserve) + return NULL; + if (!__dev_alloc_skb(length, gfp_mask|__GFP_MEMALLOC)) + return NULL;; + dev->rx_reserve_used++;
why bother with rx_reserve at all? Why not just let the second allocation fail, without the rx_reserve_used test? Additionally, I think the rx_reserve_used accounting is wrong, since I could simply free the skb -- but doing so would cause a rx_reserve_used leak in your code, since you only decrement the counter in the TCP IPv4 path.
+done:
+ skb->dev = dev;
+ return skb;
+}
+
+static inline struct sk_buff *dev_alloc_skb_reserve(struct net_device *dev,
+ unsigned length)
+{
+ return __dev_memalloc_skb(dev, length, GFP_ATOMIC);
+}unused function
quoted hunk ↗ jump to hunk
+ #endif /* __KERNEL__ */ #endif /* _LINUX_DEV_H */ diff -up --recursive 2.6.12.3.clean/include/net/sock.h 2.6.12.3/include/net/sock.h--- 2.6.12.3.clean/include/net/sock.h 2005-07-15 17:18:57.000000000 -0400 +++ 2.6.12.3/include/net/sock.h 2005-08-05 21:53:09.000000000 -0400@@ -382,6 +382,7 @@ enum sock_flags { SOCK_NO_LARGESEND, /* whether to sent large segments or not */ SOCK_LOCALROUTE, /* route locally only, %SO_DONTROUTE setting */ SOCK_QUEUE_SHRUNK, /* write queue has been shrunk recently */ + SOCK_MEMALLOC, /* protocol can use memalloc reserve */ }; static inline void sock_set_flag(struct sock *sk, enum sock_flags flag)@@ -399,6 +400,11 @@ static inline int sock_flag(struct sock return test_bit(flag, &sk->sk_flags); } +static inline int is_memalloc_sock(struct sock *sk) +{ + return sock_flag(sk, SOCK_MEMALLOC); +} + static inline void sk_acceptq_removed(struct sock *sk) { sk->sk_ack_backlog--;diff -up --recursive 2.6.12.3.clean/mm/page_alloc.c 2.6.12.3/mm/page_alloc.c--- 2.6.12.3.clean/mm/page_alloc.c 2005-07-15 17:18:57.000000000 -0400 +++ 2.6.12.3/mm/page_alloc.c 2005-08-05 21:53:09.000000000 -0400@@ -802,8 +802,8 @@ __alloc_pages(unsigned int __nocast gfp_ /* This allocation should allow future memory freeing. */ - if (((p->flags & PF_MEMALLOC) || unlikely(test_thread_flag(TIF_MEMDIE))) - && !in_interrupt()) { + if ((((p->flags & PF_MEMALLOC) || unlikely(test_thread_flag(TIF_MEMDIE))) + && !in_interrupt()) || (gfp_mask & __GFP_MEMALLOC)) { if (!(gfp_mask & __GFP_NOMEMALLOC)) { /* go through the zonelist yet again, ignoring mins */ for (i = 0; (z = zones[i]) != NULL; i++) {diff -up --recursive 2.6.12.3.clean/net/ethernet/eth.c 2.6.12.3/net/ethernet/eth.c--- 2.6.12.3.clean/net/ethernet/eth.c 2005-07-15 17:18:57.000000000 -0400 +++ 2.6.12.3/net/ethernet/eth.c 2005-08-06 02:32:02.000000000 -0400@@ -281,6 +281,7 @@ void ether_setup(struct net_device *dev) dev->mtu = 1500; /* eth_mtu */ dev->addr_len = ETH_ALEN; dev->tx_queue_len = 1000; /* Ethernet wants good queues */ + dev->rx_reserve = 50; dev->flags = IFF_BROADCAST|IFF_MULTICAST; memset(dev->broadcast,0xFF, ETH_ALEN);diff -up --recursive 2.6.12.3.clean/net/ipv4/tcp_ipv4.c 2.6.12.3/net/ipv4/tcp_ipv4.c--- 2.6.12.3.clean/net/ipv4/tcp_ipv4.c 2005-07-15 17:18:57.000000000 -0400 +++ 2.6.12.3/net/ipv4/tcp_ipv4.c 2005-08-06 00:45:07.000000000 -0400@@ -1766,6 +1766,12 @@ int tcp_v4_rcv(struct sk_buff *skb) if (!sk) goto no_tcp_socket; + if (skb->dev->rx_reserve_used) { + skb->dev->rx_reserve_used--; // racy
if its racy, use atomic_t or somesuch :) Jeff -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>