[PATCH] ipmi: add timer thread

We must poll for responses to commands when interrupts aren't in use.  The
default poll interval is based on using a kernel timer, which varies with HZ.
For character-based interfaces like KCS and SMIC though, that can be way too
slow (>15 minutes to flash a new firmware with KCS, >20 seconds to retrieve
the sensor list).

This creates a low-priority kernel thread to poll more often.  If the state
machine is idle, so is the kernel thread.  But if there's an active command,
it polls quite rapidly.  This decrease a firmware flash time from 15 minutes
to 1.5 minutes, and the sensor list time to 4.5 seconds, on a Dell PowerEdge
x8x system.

The timer-based polling remains, to ensure some amount of responsiveness even
under high user process CPU load.

Checking for a stopped timer at rmmod now uses atomics and del_timer_sync() to
ensure safe stoppage.

Signed-off-by: Matt Domsch <Matt_Domsch@dell.com>
Signed-off-by: Corey Minyard <minyard@acm.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

diff --git a/drivers/char/ipmi/ipmi_si_intf.c b/drivers/char/ipmi/ipmi_si_intf.c
index d514df7c72830dc018d234db1b6e72fe36946168..fa3be622ca97bbb4796241242126d21c9a825db3 100644 (file)
--- a/drivers/char/ipmi/ipmi_si_intf.c
+++ b/drivers/char/ipmi/ipmi_si_intf.c
@@ -126,6 +126,7 @@ struct ipmi_device_id {
 
 struct smi_info
 {
+       int                    intf_num;
        ipmi_smi_t             intf;
        struct si_sm_data      *si_sm;
        struct si_sm_handlers  *handlers;
@@ -193,8 +194,7 @@ struct smi_info
        unsigned long       last_timeout_jiffies;
 
        /* Used to gracefully stop the timer without race conditions. */
-       volatile int        stop_operation;
-       volatile int        timer_stopped;
+       atomic_t            stop_operation;
 
        /* The driver will disable interrupts when it gets into a
           situation where it cannot handle messages due to lack of
@@ -221,6 +221,9 @@ struct smi_info
        unsigned long events;
        unsigned long watchdog_pretimeouts;
        unsigned long incoming_messages;
+
+        struct completion exiting;
+        long              thread_pid;
 };
 
 static struct notifier_block *xaction_notifier_list;
@@ -779,6 +782,38 @@ static void set_run_to_completion(void *send_info, int i_run_to_completion)
        spin_unlock_irqrestore(&(smi_info->si_lock), flags);
 }
 
+static int ipmi_thread(void *data)
+{
+       struct smi_info *smi_info = data;
+       unsigned long flags, last=1;
+       enum si_sm_result smi_result;
+
+       daemonize("kipmi%d", smi_info->intf_num);
+       allow_signal(SIGKILL);
+       set_user_nice(current, 19);
+       while (!atomic_read(&smi_info->stop_operation)) {
+               schedule_timeout(last);
+               spin_lock_irqsave(&(smi_info->si_lock), flags);
+               smi_result=smi_event_handler(smi_info, 0);
+               spin_unlock_irqrestore(&(smi_info->si_lock), flags);
+               if (smi_result == SI_SM_CALL_WITHOUT_DELAY)
+                       last = 0;
+               else if (smi_result == SI_SM_CALL_WITH_DELAY) {
+                       udelay(1);
+                       last = 0;
+               }
+               else {
+                       /* System is idle; go to sleep */
+                       last = 1;
+                       current->state = TASK_INTERRUPTIBLE;
+               }
+       }
+       smi_info->thread_pid = 0;
+       complete_and_exit(&(smi_info->exiting), 0);
+       return 0;
+}
+
+
 static void poll(void *send_info)
 {
        struct smi_info *smi_info = send_info;
@@ -837,10 +872,8 @@ static void smi_timeout(unsigned long data)
        struct timeval    t;
 #endif
 
-       if (smi_info->stop_operation) {
-               smi_info->timer_stopped = 1;
+       if (atomic_read(&smi_info->stop_operation))
                return;
-       }
 
        spin_lock_irqsave(&(smi_info->si_lock), flags);
 #ifdef DEBUG_TIMING
@@ -913,7 +946,7 @@ static irqreturn_t si_irq_handler(int irq, void *data, struct pt_regs *regs)
        smi_info->interrupts++;
        spin_unlock(&smi_info->count_lock);
 
-       if (smi_info->stop_operation)
+       if (atomic_read(&smi_info->stop_operation))
                goto out;
 
 #ifdef DEBUG_TIMING
@@ -1432,7 +1465,7 @@ static u32 ipmi_acpi_gpe(void *context)
        smi_info->interrupts++;
        spin_unlock(&smi_info->count_lock);
 
-       if (smi_info->stop_operation)
+       if (atomic_read(&smi_info->stop_operation))
                goto out;
 
 #ifdef DEBUG_TIMING
@@ -2177,6 +2210,16 @@ static void setup_xaction_handlers(struct smi_info *smi_info)
        setup_dell_poweredge_bt_xaction_handler(smi_info);
 }
 
+static inline void wait_for_timer_and_thread(struct smi_info *smi_info)
+{
+       if (smi_info->thread_pid > 0) {
+               /* wake the potentially sleeping thread */
+               kill_proc(smi_info->thread_pid, SIGKILL, 0);
+               wait_for_completion(&(smi_info->exiting));
+       }
+       del_timer_sync(&smi_info->si_timer);
+}
+
 /* Returns 0 if initialized, or negative on an error. */
 static int init_one_smi(int intf_num, struct smi_info **smi)
 {
@@ -2284,8 +2327,8 @@ static int init_one_smi(int intf_num, struct smi_info **smi)
        new_smi->run_to_completion = 0;
 
        new_smi->interrupt_disabled = 0;
-       new_smi->timer_stopped = 0;
-       new_smi->stop_operation = 0;
+       atomic_set(&new_smi->stop_operation, 0);
+       new_smi->intf_num = intf_num;
 
        /* Start clearing the flags before we enable interrupts or the
           timer to avoid racing with the timer. */
@@ -2303,7 +2346,14 @@ static int init_one_smi(int intf_num, struct smi_info **smi)
        new_smi->si_timer.function = smi_timeout;
        new_smi->last_timeout_jiffies = jiffies;
        new_smi->si_timer.expires = jiffies + SI_TIMEOUT_JIFFIES;
+
        add_timer(&(new_smi->si_timer));
+       if (new_smi->si_type != SI_BT) {
+               init_completion(&(new_smi->exiting));
+               new_smi->thread_pid = kernel_thread(ipmi_thread, new_smi,
+                                                   CLONE_FS|CLONE_FILES|
+                                                   CLONE_SIGHAND);
+       }
 
        rv = ipmi_register_smi(&handlers,
                               new_smi,
@@ -2345,12 +2395,8 @@ static int init_one_smi(int intf_num, struct smi_info **smi)
        return 0;
 
  out_err_stop_timer:
-       new_smi->stop_operation = 1;
-
-       /* Wait for the timer to stop.  This avoids problems with race
-          conditions removing the timer here. */
-       while (!new_smi->timer_stopped)
-               schedule_timeout_uninterruptible(1);
+       atomic_inc(&new_smi->stop_operation);
+       wait_for_timer_and_thread(new_smi);
 
  out_err:
        if (new_smi->intf)
@@ -2456,8 +2502,7 @@ static void __exit cleanup_one_si(struct smi_info *to_clean)
        spin_lock_irqsave(&(to_clean->si_lock), flags);
        spin_lock(&(to_clean->msg_lock));
 
-       to_clean->stop_operation = 1;
-
+       atomic_inc(&to_clean->stop_operation);
        to_clean->irq_cleanup(to_clean);
 
        spin_unlock(&(to_clean->msg_lock));
@@ -2468,10 +2513,7 @@ static void __exit cleanup_one_si(struct smi_info *to_clean)
           interrupt. */
        synchronize_sched();
 
-       /* Wait for the timer to stop.  This avoids problems with race
-          conditions removing the timer here. */
-       while (!to_clean->timer_stopped)
-               schedule_timeout_uninterruptible(1);
+       wait_for_timer_and_thread(to_clean);
 
        /* Interrupts and timeouts are stopped, now make sure the
           interface is in a clean state. */