From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753950Ab0DNHmu (ORCPT ); Wed, 14 Apr 2010 03:42:50 -0400 Received: from mail-bw0-f225.google.com ([209.85.218.225]:34924 "EHLO mail-bw0-f225.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753151Ab0DNHms (ORCPT ); Wed, 14 Apr 2010 03:42:48 -0400 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=subject:from:to:cc:content-type:date:message-id:mime-version :x-mailer:content-transfer-encoding; b=DUL+jQHy/2SCpzgO0rpdt9RlUycP4GRpQy0VxPwO1/w9DjVswK0FJKSfe/xhWwN77Y xyfTsPokjGENKN02mrNCA+a2TjaRDQ6n2FmE55ITn6a6ljcttin16I35OPSd291nCcr2 9IueBIiHWcO9TlzNCc8MbVaW1RDKUUY9xKpfk= Subject: [PATCH net-next-2.6] fasync: RCU locking From: Eric Dumazet To: David Miller , "Paul E. McKenney" Cc: netdev , linux-kernel Content-Type: text/plain; charset="UTF-8" Date: Wed, 14 Apr 2010 09:42:41 +0200 Message-ID: <1271230961.16881.630.camel@edumazet-laptop> Mime-Version: 1.0 X-Mailer: Evolution 2.28.3 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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 --- 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; }