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[2001:470:b8f6:1b::1]) by smtp.gmail.com with ESMTPSA id 108sm185737oti.1.2020.02.12.05.45.53 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 12 Feb 2020 05:45:53 -0800 (PST) Received: from minyard.net (unknown [IPv6:2001:470:b8f6:1b:e166:6491:dd75:4196]) by serve.minyard.net (Postfix) with ESMTPSA id 5A6DA180053; Wed, 12 Feb 2020 13:45:53 +0000 (UTC) Date: Wed, 12 Feb 2020 07:45:52 -0600 From: Corey Minyard To: Amol Grover Cc: Arnd Bergmann , Greg Kroah-Hartman , openipmi-developer@lists.sourceforge.net, linux-kernel@vger.kernel.org, linux-kernel-mentees@lists.linuxfoundation.org, Joel Fernandes , Madhuparna Bhowmik , "Paul E . McKenney" Subject: Re: [PATCH v3] drivers: char: ipmi: ipmi_msghandler: Pass lockdep expression to RCU lists Message-ID: <20200212134552.GN7842@minyard.net> Reply-To: minyard@acm.org References: <20200117132521.31020-1-frextrite@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200117132521.31020-1-frextrite@gmail.com> User-Agent: Mutt/1.9.4 (2018-02-28) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Jan 17, 2020 at 06:55:22PM +0530, Amol Grover wrote: > intf->cmd_rcvrs is traversed with list_for_each_entry_rcu > outside an RCU read-side critical section but under the > protection of intf->cmd_rcvrs_mutex. > > ipmi_interfaces is traversed using list_for_each_entry_rcu > outside an RCU read-side critical section but under the protection > of ipmi_interfaces_mutex. > > Hence, add the corresponding lockdep expression to the list traversal > primitive to silence false-positive lockdep warnings, and > harden RCU lists. > > Add macro for the corresponding lockdep expression to make the code > clean and concise. > > Signed-off-by: Amol Grover After reading everything, I think this is correct, but I would like Paul's stamp of approval on this. Thanks, -corey > --- > v3: > - Remove rcu_read_lock_held() from lockdep expression since it is > implicitly checked. > - Remove unintended macro usage. > > v2: > - Fix sparse error > CHECK: Alignment should match open parenthesis > > drivers/char/ipmi/ipmi_msghandler.c | 14 ++++++++++---- > 1 file changed, 10 insertions(+), 4 deletions(-) > > diff --git a/drivers/char/ipmi/ipmi_msghandler.c b/drivers/char/ipmi/ipmi_msghandler.c > index cad9563f8f48..64ba16dcb681 100644 > --- a/drivers/char/ipmi/ipmi_msghandler.c > +++ b/drivers/char/ipmi/ipmi_msghandler.c > @@ -618,6 +618,8 @@ static DEFINE_MUTEX(ipmidriver_mutex); > > static LIST_HEAD(ipmi_interfaces); > static DEFINE_MUTEX(ipmi_interfaces_mutex); > +#define ipmi_interfaces_mutex_held() \ > + lockdep_is_held(&ipmi_interfaces_mutex) > static struct srcu_struct ipmi_interfaces_srcu; > > /* > @@ -1321,7 +1323,8 @@ static void _ipmi_destroy_user(struct ipmi_user *user) > * synchronize_srcu()) then free everything in that list. > */ > mutex_lock(&intf->cmd_rcvrs_mutex); > - list_for_each_entry_rcu(rcvr, &intf->cmd_rcvrs, link) { > + list_for_each_entry_rcu(rcvr, &intf->cmd_rcvrs, link, > + lockdep_is_held(&intf->cmd_rcvrs_mutex)) { > if (rcvr->user == user) { > list_del_rcu(&rcvr->link); > rcvr->next = rcvrs; > @@ -1599,7 +1602,8 @@ static struct cmd_rcvr *find_cmd_rcvr(struct ipmi_smi *intf, > { > struct cmd_rcvr *rcvr; > > - list_for_each_entry_rcu(rcvr, &intf->cmd_rcvrs, link) { > + list_for_each_entry_rcu(rcvr, &intf->cmd_rcvrs, link, > + lockdep_is_held(&intf->cmd_rcvrs_mutex)) { > if ((rcvr->netfn == netfn) && (rcvr->cmd == cmd) > && (rcvr->chans & (1 << chan))) > return rcvr; > @@ -1614,7 +1618,8 @@ static int is_cmd_rcvr_exclusive(struct ipmi_smi *intf, > { > struct cmd_rcvr *rcvr; > > - list_for_each_entry_rcu(rcvr, &intf->cmd_rcvrs, link) { > + list_for_each_entry_rcu(rcvr, &intf->cmd_rcvrs, link, > + lockdep_is_held(&intf->cmd_rcvrs_mutex)) { > if ((rcvr->netfn == netfn) && (rcvr->cmd == cmd) > && (rcvr->chans & chans)) > return 0; > @@ -3450,7 +3455,8 @@ int ipmi_add_smi(struct module *owner, > /* Look for a hole in the numbers. */ > i = 0; > link = &ipmi_interfaces; > - list_for_each_entry_rcu(tintf, &ipmi_interfaces, link) { > + list_for_each_entry_rcu(tintf, &ipmi_interfaces, link, > + ipmi_interfaces_mutex_held()) { > if (tintf->intf_num != i) { > link = &tintf->link; > break; > -- > 2.24.1 >