On 28/02/2020 08:17, Amol Grover wrote:
It is completely safe to traverse ipmi_interfaces and
intf->users under SRCU read lock using list_for_each_entry_rcu().
Tell lockdep about it as well else it will show false-positive
warnings as the one below.
Fixes the following false-positive warning and others that may follow.
[ 29.772408] =============================
[ 29.776863] WARNING: suspicious RCU usage
[ 29.780915] 5.6.0-rc3-00001-g907305ae6618-dirty #1755 Not tainted
[ 29.787046] -----------------------------
[ 29.791100] drivers/char/ipmi/ipmi_msghandler.c:744 RCU-list traversed in
non-reader section!!
Reported-by: John Garry <john.ga...@huawei.com>
Suggested-by: Paul E. McKenney <paul...@kernel.org>
Signed-off-by: Amol Grover <frextr...@gmail.com>
Tested-by: John Garry <john.ga...@huawei.com>
Thanks, the warnings have gone away with this
---
drivers/char/ipmi/ipmi_msghandler.c | 18 ++++++++++++------
1 file changed, 12 insertions(+), 6 deletions(-)
diff --git a/drivers/char/ipmi/ipmi_msghandler.c
b/drivers/char/ipmi/ipmi_msghandler.c
index cad9563f8f48..d202022c69de 100644
--- a/drivers/char/ipmi/ipmi_msghandler.c
+++ b/drivers/char/ipmi/ipmi_msghandler.c
@@ -741,7 +741,8 @@ int ipmi_smi_watcher_register(struct ipmi_smi_watcher
*watcher)
list_add(&watcher->link, &smi_watchers);
index = srcu_read_lock(&ipmi_interfaces_srcu);
- list_for_each_entry_rcu(intf, &ipmi_interfaces, link) {
+ list_for_each_entry_rcu(intf, &ipmi_interfaces, link,
+ srcu_read_lock_held(&ipmi_interfaces_srcu)) {
int intf_num = READ_ONCE(intf->intf_num);
if (intf_num == -1)
@@ -1188,7 +1189,8 @@ int ipmi_create_user(unsigned int if_num,
return -ENOMEM;
index = srcu_read_lock(&ipmi_interfaces_srcu);
- list_for_each_entry_rcu(intf, &ipmi_interfaces, link) {
+ list_for_each_entry_rcu(intf, &ipmi_interfaces, link,
+ srcu_read_lock_held(&ipmi_interfaces_srcu)) {
if (intf->intf_num == if_num)
goto found;
}
@@ -1241,7 +1243,8 @@ int ipmi_get_smi_info(int if_num, struct ipmi_smi_info
*data)
struct ipmi_smi *intf;
index = srcu_read_lock(&ipmi_interfaces_srcu);
- list_for_each_entry_rcu(intf, &ipmi_interfaces, link) {
+ list_for_each_entry_rcu(intf, &ipmi_interfaces, link,
+ srcu_read_lock_held(&ipmi_interfaces_srcu)) {
if (intf->intf_num == if_num)
goto found;
}
@@ -4098,7 +4101,8 @@ static int handle_read_event_rsp(struct ipmi_smi *intf,
* getting events.
*/
index = srcu_read_lock(&intf->users_srcu);
- list_for_each_entry_rcu(user, &intf->users, link) {
+ list_for_each_entry_rcu(user, &intf->users, link,
+ srcu_read_lock_held(&intf->users_srcu)) {
if (!user->gets_events)
continue;
@@ -4453,7 +4457,8 @@ static void handle_new_recv_msgs(struct ipmi_smi *intf)
int index;
index = srcu_read_lock(&intf->users_srcu);
- list_for_each_entry_rcu(user, &intf->users, link) {
+ list_for_each_entry_rcu(user, &intf->users, link,
+ srcu_read_lock_held(&intf->users_srcu))
{
if (user->handler->ipmi_watchdog_pretimeout)
user->handler->ipmi_watchdog_pretimeout(
user->handler_data);
@@ -4746,7 +4751,8 @@ static void ipmi_timeout(struct timer_list *unused)
return;
index = srcu_read_lock(&ipmi_interfaces_srcu);
- list_for_each_entry_rcu(intf, &ipmi_interfaces, link) {
+ list_for_each_entry_rcu(intf, &ipmi_interfaces, link,
+ srcu_read_lock_held(&ipmi_interfaces_srcu)) {
if (atomic_read(&intf->event_waiters)) {
intf->ticks_to_req_ev--;
if (intf->ticks_to_req_ev == 0) {
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