linux-kernel.vger.kernel.org archive mirror
 help / color / mirror / Atom feed
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
> 

  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 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

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20200212134552.GN7842@minyard.net \
    --to=minyard@acm.org \
    --cc=arnd@arndb.de \
    --cc=frextrite@gmail.com \
    --cc=gregkh@linuxfoundation.org \
    --cc=joel@joelfernandes.org \
    --cc=linux-kernel-mentees@lists.linuxfoundation.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=madhuparnabhowmik04@gmail.com \
    --cc=openipmi-developer@lists.sourceforge.net \
    --cc=paulmck@kernel.org \
    --subject='Re: [PATCH v3] drivers: char: ipmi: ipmi_msghandler: Pass lockdep expression to RCU lists' \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).