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Mckenney" , Amol Grover Subject: [PATCH] ipmi: Fix RCU list lockdep debugging warnings Date: Fri, 28 Feb 2020 13:47:33 +0530 Message-Id: <20200228081731.18149-1-frextrite@gmail.com> X-Mailer: git-send-email 2.25.0 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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 Suggested-by: Paul E. McKenney Signed-off-by: Amol Grover --- 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) { -- 2.25.0