ipmi: use a tasklet for handling received messages

The IPMI driver would release a lock, deliver a message, then relock.
This is obviously ugly, and this patch converts the message handler
interface to use a tasklet to schedule work.  This lets the receive
handler be called from an interrupt handler with interrupts enabled.

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>

1 files changed, 86 insertions, 55 deletions

diff --git a/drivers/char/ipmi/ipmi_msghandler.c b/drivers/char/ipmi/ipmi_msghandler.c
index 58c0e6387cf7..289ab506b79b 100644
--- a/drivers/char/ipmi/ipmi_msghandler.c
+++ b/drivers/char/ipmi/ipmi_msghandler.c
@@ -46,6 +46,7 @@
 #include <linux/init.h>
 #include <linux/proc_fs.h>
 #include <linux/rcupdate.h>
+#include <linux/interrupt.h>
 
 #define PFX "IPMI message handler: "
 
@@ -53,6 +54,8 @@
 
 static struct ipmi_recv_msg *ipmi_alloc_recv_msg(void);
 static int ipmi_init_msghandler(void);
+static void smi_recv_tasklet(unsigned long);
+static void handle_new_recv_msgs(ipmi_smi_t intf);
 
 static int initialized;
 
@@ -355,12 +358,15 @@ struct ipmi_smi {
         int curr_seq;
 
         /*
-         * Messages that were delayed for some reason (out of memory,
-         * for instance), will go in here to be processed later in a
-         * periodic timer interrupt.
+         * Messages queued for delivery.  If delivery fails (out of memory
+         * for instance), They will stay in here to be processed later in a
+         * periodic timer interrupt.  The tasklet is for handling received
+         * messages directly from the handler.
          */
         spinlock_t       waiting_msgs_lock;
         struct list_head waiting_msgs;
+        atomic_t         watchdog_pretimeouts_to_deliver;
+        struct tasklet_struct recv_tasklet;
 
         /*
          * The list of command receivers that are registered for commands
@@ -493,6 +499,8 @@ static void clean_up_interface_data(ipmi_smi_t intf)
         struct cmd_rcvr  *rcvr, *rcvr2;
         struct list_head list;
 
+        tasklet_kill(&intf->recv_tasklet);
+
         free_smi_msg_list(&intf->waiting_msgs);
         free_recv_msg_list(&intf->waiting_events);
 
@@ -2792,6 +2800,9 @@ void ipmi_poll_interface(ipmi_user_t user)
 
         if (intf->handlers->poll)
                 intf->handlers->poll(intf->send_info);
+
+        /* In case something came in */
+        handle_new_recv_msgs(intf);
 }
 EXPORT_SYMBOL(ipmi_poll_interface);
 
@@ -2860,6 +2871,10 @@ int ipmi_register_smi(struct ipmi_smi_handlers *handlers,
 #endif
         spin_lock_init(&intf->waiting_msgs_lock);
         INIT_LIST_HEAD(&intf->waiting_msgs);
+        tasklet_init(&intf->recv_tasklet,
+                     smi_recv_tasklet,
+                     (unsigned long) intf);
+        atomic_set(&intf->watchdog_pretimeouts_to_deliver, 0);
         spin_lock_init(&intf->events_lock);
         INIT_LIST_HEAD(&intf->waiting_events);
         intf->waiting_events_count = 0;
@@ -3622,11 +3637,11 @@ static int handle_bmc_rsp(ipmi_smi_t          intf,
 }
 
 /*
- * Handle a new message.  Return 1 if the message should be requeued,
+ * Handle a received message.  Return 1 if the message should be requeued,
  * 0 if the message should be freed, or -1 if the message should not
  * be freed or requeued.
  */
-static int handle_new_recv_msg(ipmi_smi_t          intf,
+static int handle_one_recv_msg(ipmi_smi_t          intf,
                                struct ipmi_smi_msg *msg)
 {
         int requeue;
@@ -3784,12 +3799,72 @@ static int handle_new_recv_msg(ipmi_smi_t          intf,
         return requeue;
 }
 
+/*
+ * If there are messages in the queue or pretimeouts, handle them.
+ */
+static void handle_new_recv_msgs(ipmi_smi_t intf)
+{
+        struct ipmi_smi_msg  *smi_msg;
+        unsigned long        flags = 0;
+        int                  rv;
+        int                  run_to_completion = intf->run_to_completion;
+
+        /* See if any waiting messages need to be processed. */
+        if (!run_to_completion)
+                spin_lock_irqsave(&intf->waiting_msgs_lock, flags);
+        while (!list_empty(&intf->waiting_msgs)) {
+                smi_msg = list_entry(intf->waiting_msgs.next,
+                                     struct ipmi_smi_msg, link);
+                list_del(&smi_msg->link);
+                if (!run_to_completion)
+                        spin_unlock_irqrestore(&intf->waiting_msgs_lock, flags);
+                rv = handle_one_recv_msg(intf, smi_msg);
+                if (!run_to_completion)
+                        spin_lock_irqsave(&intf->waiting_msgs_lock, flags);
+                if (rv == 0) {
+                        /* Message handled */
+                        ipmi_free_smi_msg(smi_msg);
+                } else if (rv < 0) {
+                        /* Fatal error on the message, del but don't free. */
+                } else {
+                        /*
+                         * To preserve message order, quit if we
+                         * can't handle a message.
+                         */
+                        list_add(&smi_msg->link, &intf->waiting_msgs);
+                        break;
+                }
+        }
+        if (!run_to_completion)
+                spin_unlock_irqrestore(&intf->waiting_msgs_lock, flags);
+
+        /*
+         * If the pretimout count is non-zero, decrement one from it and
+         * deliver pretimeouts to all the users.
+         */
+        if (atomic_add_unless(&intf->watchdog_pretimeouts_to_deliver, -1, 0)) {
+                ipmi_user_t user;
+
+                rcu_read_lock();
+                list_for_each_entry_rcu(user, &intf->users, link) {
+                        if (user->handler->ipmi_watchdog_pretimeout)
+                                user->handler->ipmi_watchdog_pretimeout(
+                                        user->handler_data);
+                }
+                rcu_read_unlock();
+        }
+}
+
+static void smi_recv_tasklet(unsigned long val)
+{
+        handle_new_recv_msgs((ipmi_smi_t) val);
+}
+
 /* Handle a new message from the lower layer. */
 void ipmi_smi_msg_received(ipmi_smi_t          intf,
                            struct ipmi_smi_msg *msg)
 {
         unsigned long flags = 0; /* keep us warning-free. */
-        int           rv;
         int           run_to_completion;
 
 
@@ -3843,31 +3918,11 @@ void ipmi_smi_msg_received(ipmi_smi_t          intf,
         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);
-                if (!run_to_completion)
-                        spin_unlock_irqrestore(&intf->waiting_msgs_lock, flags);
-                goto out;
-        }
+        list_add_tail(&msg->link, &intf->waiting_msgs);
         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.
-                 */
-                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);
-                if (!run_to_completion)
-                        spin_unlock_irqrestore(&intf->waiting_msgs_lock, flags);
-        } else if (rv == 0) {
-                ipmi_free_smi_msg(msg);
-        }
-
+        tasklet_schedule(&intf->recv_tasklet);
  out:
         return;
 }
@@ -3875,16 +3930,8 @@ EXPORT_SYMBOL(ipmi_smi_msg_received);
 
 void ipmi_smi_watchdog_pretimeout(ipmi_smi_t intf)
 {
-        ipmi_user_t user;
-
-        rcu_read_lock();
-        list_for_each_entry_rcu(user, &intf->users, link) {
-                if (!user->handler->ipmi_watchdog_pretimeout)
-                        continue;
-
-                user->handler->ipmi_watchdog_pretimeout(user->handler_data);
-        }
-        rcu_read_unlock();
+        atomic_set(&intf->watchdog_pretimeouts_to_deliver, 1);
+        tasklet_schedule(&intf->recv_tasklet);
 }
 EXPORT_SYMBOL(ipmi_smi_watchdog_pretimeout);
 
@@ -3998,28 +4045,12 @@ static void ipmi_timeout_handler(long timeout_period)
         ipmi_smi_t           intf;
         struct list_head     timeouts;
         struct ipmi_recv_msg *msg, *msg2;
-        struct ipmi_smi_msg  *smi_msg, *smi_msg2;
         unsigned long        flags;
         int                  i;
 
         rcu_read_lock();
         list_for_each_entry_rcu(intf, &ipmi_interfaces, link) {
-                /* See if any waiting messages need to be processed. */
-                spin_lock_irqsave(&intf->waiting_msgs_lock, flags);
-                list_for_each_entry_safe(smi_msg, smi_msg2,
-                                         &intf->waiting_msgs, link) {
-                        if (!handle_new_recv_msg(intf, smi_msg)) {
-                                list_del(&smi_msg->link);
-                                ipmi_free_smi_msg(smi_msg);
-                        } else {
-                                /*
-                                 * To preserve message order, quit if we
-                                 * can't handle a message.
-                                 */
-                                break;
-                        }
-                }
-                spin_unlock_irqrestore(&intf->waiting_msgs_lock, flags);
+                tasklet_schedule(&intf->recv_tasklet);
 
                 /*
                  * Go through the seq table and find any messages that