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net: sock_def_readable() and friends RCU conversion

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sk_callback_lock rwlock actually protects sk->sk_sleep pointer, so we
need two atomic operations (and associated dirtying) per incoming
packet.

RCU conversion is pretty much needed :

1) Add a new structure, called "struct socket_wq" to hold all fields
that will need rcu_read_lock() protection (currently: a
wait_queue_head_t and a struct fasync_struct pointer).

[Future patch will add a list anchor for wakeup coalescing]

2) Attach one of such structure to each "struct socket" created in
sock_alloc_inode().

3) Respect RCU grace period when freeing a "struct socket_wq"

4) Change sk_sleep pointer in "struct sock" by sk_wq, pointer to "struct
socket_wq"

5) Change sk_sleep() function to use new sk->sk_wq instead of
sk->sk_sleep

6) Change sk_has_sleeper() to wq_has_sleeper() that must be used inside
a rcu_read_lock() section.

7) Change all sk_has_sleeper() callers to :
  - Use rcu_read_lock() instead of read_lock(&sk->sk_callback_lock)
  - Use wq_has_sleeper() to eventually wakeup tasks.
  - Use rcu_read_unlock() instead of read_unlock(&sk->sk_callback_lock)

8) sock_wake_async() is modified to use rcu protection as well.

9) Exceptions :
  macvtap, drivers/net/tun.c, af_unix use integrated "struct socket_wq"
instead of dynamically allocated ones. They dont need rcu freeing.

Some cleanups or followups are probably needed, (possible
sk_callback_lock conversion to a spinlock for example...).

Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Eric Dumazet
2010-04-29 11:01:49 +00:00
committed by David S. Miller
parent 83d7eb2979
commit 4381548237
16 changed files with 181 additions and 114 deletions
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20
include/net/af_unix.h
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@@ -30,7 +30,7 @@ struct unix_skb_parms {
#endif
};
#define UNIXCB(skb) (*(struct unix_skb_parms*)&((skb)->cb))
#define UNIXCB(skb) (*(struct unix_skb_parms *)&((skb)->cb))
#define UNIXCREDS(skb) (&UNIXCB((skb)).creds)
#define UNIXSID(skb) (&UNIXCB((skb)).secid)
@@ -45,21 +45,23 @@ struct unix_skb_parms {
struct unix_sock {
/* WARNING: sk has to be the first member */
struct sock sk;
struct unix_address *addr;
struct dentry *dentry;
struct vfsmount *mnt;
struct unix_address *addr;
struct dentry *dentry;
struct vfsmount *mnt;
struct mutex readlock;
struct sock *peer;
struct sock *other;
struct sock *peer;
struct sock *other;
struct list_head link;
atomic_long_t inflight;
spinlock_t lock;
atomic_long_t inflight;
spinlock_t lock;
unsigned int gc_candidate : 1;
unsigned int gc_maybe_cycle : 1;
wait_queue_head_t peer_wait;
struct socket_wq peer_wq;
};
#define unix_sk(__sk) ((struct unix_sock *)__sk)
#define peer_wait peer_wq.wait
#ifdef CONFIG_SYSCTL
extern int unix_sysctl_register(struct net *net);
extern void unix_sysctl_unregister(struct net *net);