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Message-ID: <1271230961.16881.630.camel@edumazet-laptop>
Date: Wed, 14 Apr 2010 09:42:41 +0200
From: Eric Dumazet <eric.dumazet@...il.com>
To: David Miller <davem@...emloft.net>,
"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
Cc: netdev <netdev@...r.kernel.org>,
linux-kernel <linux-kernel@...r.kernel.org>
Subject: [PATCH net-next-2.6] fasync: RCU locking
Paul, could you please check this patch, I am not sure
of the IRQ safety thing...
Is call_rcu() the right method to use in this case ?
Thanks
[PATCH net-next-2.6] fasync: RCU locking
kill_fasync() uses a central rwlock, candidate for RCU conversion.
We can remove __kill_fasync() direct use in net, and rename it to
kill_fasync_rcu()
Signed-off-by: Eric Dumazet <eric.dumazet@...il.com>
---
fs/fcntl.c | 36 +++++++++++++++++++++---------------
include/linux/fs.h | 11 +++++------
net/socket.c | 4 ++--
3 files changed, 28 insertions(+), 23 deletions(-)
diff --git a/fs/fcntl.c b/fs/fcntl.c
index 452d02f..33cb3ee 100644
--- a/fs/fcntl.c
+++ b/fs/fcntl.c
@@ -614,9 +614,15 @@ int send_sigurg(struct fown_struct *fown)
return ret;
}
-static DEFINE_RWLOCK(fasync_lock);
+static DEFINE_SPINLOCK(fasync_lock);
static struct kmem_cache *fasync_cache __read_mostly;
+static void fasync_free_rcu(struct rcu_head *head)
+{
+ kmem_cache_free(fasync_cache,
+ container_of(head, struct fasync_struct, fa_rcu));
+}
+
/*
* Remove a fasync entry. If successfully removed, return
* positive and clear the FASYNC flag. If no entry exists,
@@ -634,17 +640,17 @@ static int fasync_remove_entry(struct file *filp, struct fasync_struct **fapp)
int result = 0;
spin_lock(&filp->f_lock);
- write_lock_irq(&fasync_lock);
+ spin_lock_irq(&fasync_lock);
for (fp = fapp; (fa = *fp) != NULL; fp = &fa->fa_next) {
if (fa->fa_file != filp)
continue;
*fp = fa->fa_next;
- kmem_cache_free(fasync_cache, fa);
+ call_rcu(&fa->fa_rcu, fasync_free_rcu);
filp->f_flags &= ~FASYNC;
result = 1;
break;
}
- write_unlock_irq(&fasync_lock);
+ spin_unlock_irq(&fasync_lock);
spin_unlock(&filp->f_lock);
return result;
}
@@ -666,7 +672,7 @@ static int fasync_add_entry(int fd, struct file *filp, struct fasync_struct **fa
return -ENOMEM;
spin_lock(&filp->f_lock);
- write_lock_irq(&fasync_lock);
+ spin_lock_irq(&fasync_lock);
for (fp = fapp; (fa = *fp) != NULL; fp = &fa->fa_next) {
if (fa->fa_file != filp)
continue;
@@ -679,12 +685,12 @@ static int fasync_add_entry(int fd, struct file *filp, struct fasync_struct **fa
new->fa_file = filp;
new->fa_fd = fd;
new->fa_next = *fapp;
- *fapp = new;
+ rcu_assign_pointer(*fapp, new);
result = 1;
filp->f_flags |= FASYNC;
out:
- write_unlock_irq(&fasync_lock);
+ spin_unlock_irq(&fasync_lock);
spin_unlock(&filp->f_lock);
return result;
}
@@ -704,7 +710,10 @@ int fasync_helper(int fd, struct file * filp, int on, struct fasync_struct **fap
EXPORT_SYMBOL(fasync_helper);
-void __kill_fasync(struct fasync_struct *fa, int sig, int band)
+/*
+ * rcu_read_lock() is held
+ */
+static void kill_fasync_rcu(struct fasync_struct *fa, int sig, int band)
{
while (fa) {
struct fown_struct * fown;
@@ -719,22 +728,19 @@ void __kill_fasync(struct fasync_struct *fa, int sig, int band)
mechanism. */
if (!(sig == SIGURG && fown->signum == 0))
send_sigio(fown, fa->fa_fd, band);
- fa = fa->fa_next;
+ fa = rcu_dereference(fa->fa_next);
}
}
-EXPORT_SYMBOL(__kill_fasync);
-
void kill_fasync(struct fasync_struct **fp, int sig, int band)
{
/* First a quick test without locking: usually
* the list is empty.
*/
if (*fp) {
- read_lock(&fasync_lock);
- /* reread *fp after obtaining the lock */
- __kill_fasync(*fp, sig, band);
- read_unlock(&fasync_lock);
+ rcu_read_lock();
+ kill_fasync_rcu(rcu_dereference(*fp), sig, band);
+ rcu_read_unlock();
}
}
EXPORT_SYMBOL(kill_fasync);
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 39d57bc..158b2cc 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -1280,10 +1280,11 @@ static inline int lock_may_write(struct inode *inode, loff_t start,
struct fasync_struct {
- int magic;
- int fa_fd;
- struct fasync_struct *fa_next; /* singly linked list */
- struct file *fa_file;
+ int magic;
+ int fa_fd;
+ struct fasync_struct *fa_next; /* singly linked list */
+ struct file *fa_file;
+ struct rcu_head fa_rcu;
};
#define FASYNC_MAGIC 0x4601
@@ -1292,8 +1293,6 @@ struct fasync_struct {
extern int fasync_helper(int, struct file *, int, struct fasync_struct **);
/* can be called from interrupts */
extern void kill_fasync(struct fasync_struct **, int, int);
-/* only for net: no internal synchronization */
-extern void __kill_fasync(struct fasync_struct *, int, int);
extern int __f_setown(struct file *filp, struct pid *, enum pid_type, int force);
extern int f_setown(struct file *filp, unsigned long arg, int force);
diff --git a/net/socket.c b/net/socket.c
index 35bc198..846739c 100644
--- a/net/socket.c
+++ b/net/socket.c
@@ -1159,10 +1159,10 @@ 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;
}
--
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