xiaomi-sm8450/android_kernel_xiaomi_sm8450
1
0
Fork 0
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity

fasync: RCU and fine grained locking

Browse Source 
kill_fasync() uses a central rwlock, candidate for RCU conversion, to
avoid cache line ping pongs on SMP.

fasync_remove_entry() and fasync_add_entry() can disable IRQS on a short
section instead during whole list scan.

Use a spinlock per fasync_struct to synchronize kill_fasync_rcu() and
fasync_{remove|add}_entry(). This spinlock is IRQ safe, so sock_fasync()
doesnt need its own implementation and can use fasync_helper(), to
reduce code size and complexity.

We can remove __kill_fasync() direct use in net/socket.c, and rename it
to kill_fasync_rcu().

Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Lai Jiangshan <laijs@cn.fujitsu.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Eric Dumazet
2010-04-14 09:55:35 +00:00
committed by David S. Miller
parent e5700aff14
commit 989a297920
3 changed files with 59 additions and 92 deletions
Download Patch File Download Diff File Expand all files Collapse all files

73
net/socket.c
View File

@@ -1067,78 +1067,27 @@ static int sock_close(struct inode *inode, struct file *filp)
* 1. fasync_list is modified only under process context socket lock
* i.e. under semaphore.
* 2. fasync_list is used under read_lock(&sk->sk_callback_lock)
* or under socket lock.
* 3. fasync_list can be used from softirq context, so that
* modification under socket lock have to be enhanced with
* write_lock_bh(&sk->sk_callback_lock).
* --ANK (990710)
* or under socket lock
*/
static int sock_fasync(int fd, struct file *filp, int on)
{
struct fasync_struct *fa, *fna = NULL, **prev;
struct socket *sock;
struct sock *sk;
struct socket *sock = filp->private_data;
struct sock *sk = sock->sk;
if (on) {
fna = kmalloc(sizeof(struct fasync_struct), GFP_KERNEL);
if (fna == NULL)
return -ENOMEM;
}
sock = filp->private_data;
sk = sock->sk;
if (sk == NULL) {
kfree(fna);
if (sk == NULL)
return -EINVAL;
}
lock_sock(sk);
spin_lock(&filp->f_lock);
if (on)
filp->f_flags |= FASYNC;
fasync_helper(fd, filp, on, &sock->fasync_list);
if (!sock->fasync_list)
sock_reset_flag(sk, SOCK_FASYNC);
else
filp->f_flags &= ~FASYNC;
spin_unlock(&filp->f_lock);
prev = &(sock->fasync_list);
for (fa = *prev; fa != NULL; prev = &fa->fa_next, fa = *prev)
if (fa->fa_file == filp)
break;
if (on) {
if (fa != NULL) {
write_lock_bh(&sk->sk_callback_lock);
fa->fa_fd = fd;
write_unlock_bh(&sk->sk_callback_lock);
kfree(fna);
goto out;
}
fna->fa_file = filp;
fna->fa_fd = fd;
fna->magic = FASYNC_MAGIC;
fna->fa_next = sock->fasync_list;
write_lock_bh(&sk->sk_callback_lock);
sock->fasync_list = fna;
sock_set_flag(sk, SOCK_FASYNC);
write_unlock_bh(&sk->sk_callback_lock);
} else {
if (fa != NULL) {
write_lock_bh(&sk->sk_callback_lock);
*prev = fa->fa_next;
if (!sock->fasync_list)
sock_reset_flag(sk, SOCK_FASYNC);
write_unlock_bh(&sk->sk_callback_lock);
kfree(fa);
}
}
out:
release_sock(sock->sk);
release_sock(sk);
return 0;
}
@@ -1159,10 +1108,10 @@ int sock_wake_async(struct socket *sock, int how, int band)
/* fall through */
case SOCK_WAKE_IO:
call_kill:
__kill_fasync(sock->fasync_list, SIGIO, band);
kill_fasync(&sock->fasync_list, SIGIO, band);
break;
case SOCK_WAKE_URG:
__kill_fasync(sock->fasync_list, SIGURG, band);
kill_fasync(&sock->fasync_list, SIGURG, band);
}
return 0;
}