Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S262910AbVCWU1O (ORCPT ); Wed, 23 Mar 2005 15:27:14 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S262891AbVCWUZB (ORCPT ); Wed, 23 Mar 2005 15:25:01 -0500 Received: from mx1.redhat.com ([66.187.233.31]:54919 "EHLO mx1.redhat.com") by vger.kernel.org with ESMTP id S262902AbVCWUTy (ORCPT ); Wed, 23 Mar 2005 15:19:54 -0500 From: David Howells In-Reply-To: <29204.1111608899@redhat.com> References: <29204.1111608899@redhat.com> To: torvalds@osdl.org, akpm@osdl.org, Michael A Halcrow Cc: linux-kernel@vger.kernel.org Subject: Re: [PATCH 2/3] Keys: Use RCU to manage session keyring pointer X-Mailer: MH-E 7.82; nmh 1.0.4; GNU Emacs 21.3.50.1 Date: Wed, 23 Mar 2005 20:19:45 +0000 Message-ID: <29285.1111609185@redhat.com> Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 5103 Lines: 138 The attached patch uses RCU to manage the session keyring pointer in struct signal_struct. This means that searching need not disable interrupts and get a the sighand spinlock to access this pointer. Furthermore, by judicious use of rcu_read_(un)lock(), this patch also avoids the need to take and put refcounts on the session keyring itself, thus saving on even more atomic ops. Signed-Off-By: David Howells --- warthog>diffstat -p1 keys-rcu-session-2612rc1mm1.diff security/keys/process_keys.c | 42 +++++++++++++++++++++--------------------- security/keys/request_key.c | 7 +++---- 2 files changed, 24 insertions(+), 25 deletions(-) diff -uNrp linux-2.6.12-rc1-mm1-keys-umhelper/security/keys/process_keys.c linux-2.6.12-rc1-mm1-keys-rcu-session/security/keys/process_keys.c --- linux-2.6.12-rc1-mm1-keys-umhelper/security/keys/process_keys.c 2005-03-23 17:22:46.000000000 +0000 +++ linux-2.6.12-rc1-mm1-keys-rcu-session/security/keys/process_keys.c 2005-03-23 18:27:12.055768099 +0000 @@ -1,6 +1,6 @@ /* process_keys.c: management of a process's keyrings * - * Copyright (C) 2004 Red Hat, Inc. All Rights Reserved. + * Copyright (C) 2004-5 Red Hat, Inc. All Rights Reserved. * Written by David Howells (dhowells@redhat.com) * * This program is free software; you can redistribute it and/or @@ -181,7 +181,7 @@ static int install_process_keyring(struc goto error; } - /* attach or swap keyrings */ + /* attach keyring */ spin_lock_irqsave(&tsk->sighand->siglock, flags); if (!tsk->signal->process_keyring) { tsk->signal->process_keyring = keyring; @@ -227,12 +227,14 @@ static int install_session_keyring(struc /* install the keyring */ spin_lock_irqsave(&tsk->sighand->siglock, flags); - old = tsk->signal->session_keyring; - tsk->signal->session_keyring = keyring; + old = rcu_dereference(tsk->signal->session_keyring); + rcu_assign_pointer(tsk->signal->session_keyring, keyring); spin_unlock_irqrestore(&tsk->sighand->siglock, flags); ret = 0; + /* we're using RCU on the pointer */ + synchronize_kernel(); key_put(old); error: return ret; @@ -245,8 +247,6 @@ static int install_session_keyring(struc */ int copy_thread_group_keys(struct task_struct *tsk) { - unsigned long flags; - key_check(current->thread_group->session_keyring); key_check(current->thread_group->process_keyring); @@ -254,10 +254,10 @@ int copy_thread_group_keys(struct task_s tsk->signal->process_keyring = NULL; /* same session keyring */ - spin_lock_irqsave(¤t->sighand->siglock, flags); + rcu_read_lock(); tsk->signal->session_keyring = - key_get(current->signal->session_keyring); - spin_unlock_irqrestore(¤t->sighand->siglock, flags); + key_get(rcu_dereference(current->signal->session_keyring)); + rcu_read_unlock(); return 0; @@ -381,8 +381,7 @@ struct key *search_process_keyrings_aux( key_match_func_t match) { struct task_struct *tsk = current; - unsigned long flags; - struct key *key, *ret, *err, *tmp; + struct key *key, *ret, *err; /* we want to return -EAGAIN or -ENOKEY if any of the keyrings were * searchable, but we failed to find a key or we found a negative key; @@ -436,17 +435,18 @@ struct key *search_process_keyrings_aux( } /* search the session keyring last */ - spin_lock_irqsave(&tsk->sighand->siglock, flags); - - tmp = tsk->signal->session_keyring; - if (!tmp) - tmp = tsk->user->session_keyring; - atomic_inc(&tmp->usage); - - spin_unlock_irqrestore(&tsk->sighand->siglock, flags); + if (tsk->signal->session_keyring) { + rcu_read_lock(); + key = keyring_search_aux( + rcu_dereference(tsk->signal->session_keyring), + type, description, match); + rcu_read_unlock(); + } + else { + key = keyring_search_aux(tsk->user->session_keyring, + type, description, match); + } - key = keyring_search_aux(tmp, type, description, match); - key_put(tmp); if (!IS_ERR(key)) goto found; diff -uNrp linux-2.6.12-rc1-mm1-keys-umhelper/security/keys/request_key.c linux-2.6.12-rc1-mm1-keys-rcu-session/security/keys/request_key.c --- linux-2.6.12-rc1-mm1-keys-umhelper/security/keys/request_key.c 2005-03-23 17:35:16.000000000 +0000 +++ linux-2.6.12-rc1-mm1-keys-rcu-session/security/keys/request_key.c 2005-03-23 18:14:13.908029567 +0000 @@ -175,13 +175,12 @@ static struct key *__request_key_constru key->expiry = now.tv_sec + key_negative_timeout; if (current->signal->session_keyring) { - unsigned long flags; struct key *keyring; - spin_lock_irqsave(¤t->sighand->siglock, flags); - keyring = current->signal->session_keyring; + rcu_read_lock(); + keyring = rcu_dereference(current->signal->session_keyring); atomic_inc(&keyring->usage); - spin_unlock_irqrestore(¤t->sighand->siglock, flags); + rcu_read_unlock(); key_link(keyring, key); key_put(keyring); - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/