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McKenney" Cc: Amol Grover , 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 Subject: Re: [PATCH v3] drivers: char: ipmi: ipmi_msghandler: Pass lockdep expression to RCU lists Message-ID: <20200213130407.GQ7842@minyard.net> Reply-To: minyard@acm.org References: <20200117132521.31020-1-frextrite@gmail.com> <20200212134552.GN7842@minyard.net> <20200212214956.GT2935@paulmck-ThinkPad-P72> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200212214956.GT2935@paulmck-ThinkPad-P72> 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 Wed, Feb 12, 2020 at 01:49:56PM -0800, Paul E. McKenney wrote: > On Wed, Feb 12, 2020 at 07:45:52AM -0600, Corey Minyard wrote: > > 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. > > Acked-by: Paul E. McKenney > > But note that I did not trace the locking in the case of ipmi_add_smi(). > I did the others, so lockdep can do the last one. ;-) Thanks, it's in my queue for 5.7. -corey > > Thanx, Paul > > > 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 > > >