ipmi: don't grab locks in run-to-completion mode

This patch prevents deadlocks in IPMI panic handler caused by msg_lock
in smi_info structure and waiting_msgs_lock in ipmi_smi structure.

[cminyard@mvista.com: remove unnecessary memory barriers]
Signed-off-by: Konstantin Baydarov <kbaidarov@ru.mvista.com>
Signed-off-by: Corey Minyard <cminyard@mvista.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

2 files changed, 28 insertions, 8 deletions

diff --git a/drivers/char/ipmi/ipmi_msghandler.c b/drivers/char/ipmi/ipmi_msghandler.c
index 9f0075ca34ba..8b71f5638b60 100644
--- a/drivers/char/ipmi/ipmi_msghandler.c
+++ b/drivers/char/ipmi/ipmi_msghandler.c
@@ -351,8 +351,16 @@ struct ipmi_smi
 
         /* Invalid data in an event. */
         unsigned int invalid_events;
+
         /* Events that were received with the proper format. */
         unsigned int events;
+
+        /*
+         * run_to_completion duplicate of smb_info, smi_info
+         * and ipmi_serial_info structures. Used to decrease numbers of
+         * parameters passed by "low" level IPMI code.
+         */
+        int run_to_completion;
 };
 #define to_si_intf_from_dev(device) container_of(device, struct ipmi_smi, dev)
 
@@ -3451,8 +3459,9 @@ static int handle_new_recv_msg(ipmi_smi_t          intf,
 void ipmi_smi_msg_received(ipmi_smi_t          intf,
                            struct ipmi_smi_msg *msg)
 {
-        unsigned long flags;
+        unsigned long flags = 0; /* keep us warning-free. */
         int           rv;
+        int           run_to_completion;
 
 
         if ((msg->data_size >= 2)
@@ -3501,21 +3510,28 @@ void ipmi_smi_msg_received(ipmi_smi_t          intf,
 
         /* To preserve message order, if the list is not empty, we
            tack this message onto the end of the list. */
-        spin_lock_irqsave(&intf->waiting_msgs_lock, flags);
+        run_to_completion = intf->run_to_completion;
+        if (!run_to_completion)
+                spin_lock_irqsave(&intf->waiting_msgs_lock, flags);
         if (!list_empty(&intf->waiting_msgs)) {
                 list_add_tail(&msg->link, &intf->waiting_msgs);
-                spin_unlock_irqrestore(&intf->waiting_msgs_lock, flags);
+                if (!run_to_completion)
+                        spin_unlock_irqrestore(&intf->waiting_msgs_lock, flags);
                 goto out;
         }
-        spin_unlock_irqrestore(&intf->waiting_msgs_lock, flags);
+        if (!run_to_completion)
+                spin_unlock_irqrestore(&intf->waiting_msgs_lock, flags);
                 
         rv = handle_new_recv_msg(intf, msg);
         if (rv > 0) {
                 /* Could not handle the message now, just add it to a
                    list to handle later. */
-                spin_lock_irqsave(&intf->waiting_msgs_lock, flags);
+                run_to_completion = intf->run_to_completion;
+                if (!run_to_completion)
+                        spin_lock_irqsave(&intf->waiting_msgs_lock, flags);
                 list_add_tail(&msg->link, &intf->waiting_msgs);
-                spin_unlock_irqrestore(&intf->waiting_msgs_lock, flags);
+                if (!run_to_completion)
+                        spin_unlock_irqrestore(&intf->waiting_msgs_lock, flags);
         } else if (rv == 0) {
                 ipmi_free_smi_msg(msg);
         }
@@ -3884,6 +3900,7 @@ static void send_panic_events(char *str)
                         /* Interface is not ready. */
                         continue;
 
+                intf->run_to_completion = 1;
                 /* Send the event announcing the panic. */
                 intf->handlers->set_run_to_completion(intf->send_info, 1);
                 i_ipmi_request(NULL,
@@ -4059,6 +4076,7 @@ static int panic_event(struct notifier_block *this,
                         /* Interface is not ready. */
                         continue;
 
+                intf->run_to_completion = 1;
                 intf->handlers->set_run_to_completion(intf->send_info, 1);
         }
 
diff --git a/drivers/char/ipmi/ipmi_si_intf.c b/drivers/char/ipmi/ipmi_si_intf.c
index 30f535657342..657034febdaf 100644
--- a/drivers/char/ipmi/ipmi_si_intf.c
+++ b/drivers/char/ipmi/ipmi_si_intf.c
@@ -289,7 +289,8 @@ static enum si_sm_result start_next_msg(struct smi_info *smi_info)
 
         /* No need to save flags, we aleady have interrupts off and we
            already hold the SMI lock. */
-        spin_lock(&(smi_info->msg_lock));
+        if (!smi_info->run_to_completion)
+                spin_lock(&(smi_info->msg_lock));
 
         /* Pick the high priority queue first. */
         if (!list_empty(&(smi_info->hp_xmit_msgs))) {
@@ -329,7 +330,8 @@ static enum si_sm_result start_next_msg(struct smi_info *smi_info)
                 rv = SI_SM_CALL_WITHOUT_DELAY;
         }
         out:
-        spin_unlock(&(smi_info->msg_lock));
+        if (!smi_info->run_to_completion)
+                spin_unlock(&(smi_info->msg_lock));
 
         return rv;
 }