From: Corey Minyard <minyard@acm.org>
To: Amol Grover <frextrite@gmail.com>
Cc: Arnd Bergmann <arnd@arndb.de>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
openipmi-developer@lists.sourceforge.net,
linux-kernel@vger.kernel.org,
linux-kernel-mentees@lists.linuxfoundation.org,
Joel Fernandes <joel@joelfernandes.org>,
Madhuparna Bhowmik <madhuparnabhowmik04@gmail.com>,
"Paul E . McKenney" <paulmck@kernel.org>
Subject: Re: [PATCH v3] drivers: char: ipmi: ipmi_msghandler: Pass lockdep expression to RCU lists
Date: Wed, 12 Feb 2020 07:45:52 -0600 [thread overview]
Message-ID: <20200212134552.GN7842@minyard.net> (raw)
In-Reply-To: <20200117132521.31020-1-frextrite@gmail.com>
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 <frextrite@gmail.com>
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
>
next prev parent reply other threads:[~2020-02-12 13:46 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-01-17 13:25 [PATCH v3] drivers: char: ipmi: ipmi_msghandler: Pass lockdep expression to RCU lists Amol Grover
2020-02-12 13:45 ` Corey Minyard [this message]
2020-02-12 21:49 ` Paul E. McKenney
2020-02-13 13:04 ` Corey Minyard
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