[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>

1 files changed, 63 insertions, 21 deletions

diff --git a/drivers/char/ipmi/ipmi_si_intf.c b/drivers/char/ipmi/ipmi_si_intf.c
index d514df7c7283..fa3be622ca97 100644
--- 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. */