1 files changed, 27 insertions, 24 deletions

diff --git a/arch/mips/kernel/smp.c b/arch/mips/kernel/smp.c
index af5cd3b8a396..fcacf1aae98a 100644
--- a/arch/mips/kernel/smp.c
+++ b/arch/mips/kernel/smp.c
@@ -50,7 +50,6 @@ static void smp_tune_scheduling (void)
 {
         struct cache_desc *cd = &current_cpu_data.scache;
         unsigned long cachesize;       /* kB   */
-        unsigned long bandwidth = 350; /* MB/s */
         unsigned long cpu_khz;
 
         /*
@@ -121,7 +120,19 @@ struct call_data_struct *call_data;
  * or are or have executed.
  *
  * You must not call this function with disabled interrupts or from a
- * hardware interrupt handler or from a bottom half handler.
+ * hardware interrupt handler or from a bottom half handler:
+ *
+ * CPU A                               CPU B
+ * Disable interrupts
+ *                                     smp_call_function()
+ *                                     Take call_lock
+ *                                     Send IPIs
+ *                                     Wait for all cpus to acknowledge IPI
+ *                                     CPU A has not responded, spin waiting
+ *                                     for cpu A to respond, holding call_lock
+ * smp_call_function()
+ * Spin waiting for call_lock
+ * Deadlock                            Deadlock
  */
 int smp_call_function (void (*func) (void *info), void *info, int retry,
                                                                 int wait)
@@ -130,6 +141,11 @@ int smp_call_function (void (*func) (void *info), void *info, int retry,
         int i, cpus = num_online_cpus() - 1;
         int cpu = smp_processor_id();
 
+        /*
+         * Can die spectacularly if this CPU isn't yet marked online
+         */
+        BUG_ON(!cpu_online(cpu));
+
         if (!cpus)
                 return 0;
 
@@ -214,7 +230,6 @@ void __init smp_cpus_done(unsigned int max_cpus)
 /* called from main before smp_init() */
 void __init smp_prepare_cpus(unsigned int max_cpus)
 {
-        cpu_data[0].udelay_val = loops_per_jiffy;
         init_new_context(current, &init_mm);
         current_thread_info()->cpu = 0;
         smp_tune_scheduling();
@@ -236,23 +251,28 @@ void __devinit smp_prepare_boot_cpu(void)
 }
 
 /*
- * Startup the CPU with this logical number
+ * Called once for each "cpu_possible(cpu)".  Needs to spin up the cpu
+ * and keep control until "cpu_online(cpu)" is set.  Note: cpu is
+ * physical, not logical.
  */
-static int __init do_boot_cpu(int cpu)
+int __devinit __cpu_up(unsigned int cpu)
 {
         struct task_struct *idle;
 
         /*
+         * Processor goes to start_secondary(), sets online flag
          * The following code is purely to make sure
          * Linux can schedule processes on this slave.
          */
         idle = fork_idle(cpu);
         if (IS_ERR(idle))
-                panic("failed fork for CPU %d\n", cpu);
+                panic(KERN_ERR "Fork failed for CPU %d", cpu);
 
         prom_boot_secondary(cpu, idle);
 
-        /* XXXKW timeout */
+        /*
+         * Trust is futile.  We should really have timeouts ...
+         */
         while (!cpu_isset(cpu, cpu_callin_map))
                 udelay(100);
 
@@ -261,23 +281,6 @@ static int __init do_boot_cpu(int cpu)
         return 0;
 }
 
-/*
- * Called once for each "cpu_possible(cpu)".  Needs to spin up the cpu
- * and keep control until "cpu_online(cpu)" is set.  Note: cpu is
- * physical, not logical.
- */
-int __devinit __cpu_up(unsigned int cpu)
-{
-        int ret;
-
-        /* Processor goes to start_secondary(), sets online flag */
-        ret = do_boot_cpu(cpu);
-        if (ret < 0)
-                return ret;
-
-        return 0;
-}
-
 /* Not really SMP stuff ... */
 int setup_profiling_timer(unsigned int multiplier)
 {