[MIPS] R2: Implement shadow register allocation without spinlock.

Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

diff --git a/arch/mips/kernel/traps.c b/arch/mips/kernel/traps.c
index 61efc61..081e6ed 100644 (file)
--- a/arch/mips/kernel/traps.c
+++ b/arch/mips/kernel/traps.c
@@ -961,15 +961,19 @@ void *set_except_vector(int n, void *addr)
 
 #ifdef CONFIG_CPU_MIPSR2
 /*
- * Shadow register allocation
+ * MIPSR2 shadow register set allocation
  * FIXME: SMP...
  */
 
-/* MIPSR2 shadow register sets */
-struct shadow_registers {
-       spinlock_t sr_lock;     /*  */
-       int sr_supported;       /* Number of shadow register sets supported */
-       int sr_allocated;       /* Bitmap of allocated shadow registers */
+static struct shadow_registers {
+       /*
+        * Number of shadow register sets supported
+        */
+       unsigned long sr_supported;
+       /*
+        * Bitmap of allocated shadow registers
+        */
+       unsigned long sr_allocated;
 } shadow_registers;
 
 void mips_srs_init(void)
@@ -980,7 +984,6 @@ void mips_srs_init(void)
               shadow_registers.sr_supported);
 #endif
        shadow_registers.sr_allocated = 1;      /* Set 0 used by kernel */
-       spin_lock_init(&shadow_registers.sr_lock);
 }
 
 int mips_srs_max(void)
@@ -991,32 +994,24 @@ int mips_srs_max(void)
 int mips_srs_alloc(void)
 {
        struct shadow_registers *sr = &shadow_registers;
-       unsigned long flags;
        int set;
 
-       spin_lock_irqsave(&sr->sr_lock, flags);
+again:
+       set = find_first_zero_bit(&sr->sr_allocated, sr->sr_supported);
+       if (set >= sr->sr_supported)
+               return -1;
 
-       for (set = 0; set < sr->sr_supported; set++) {
-               if ((sr->sr_allocated & (1 << set)) == 0) {
-                       sr->sr_allocated |= 1 << set;
-                       spin_unlock_irqrestore(&sr->sr_lock, flags);
-                       return set;
-               }
-       }
+       if (test_and_set_bit(set, &sr->sr_allocated))
+               goto again;
 
-       /* None available */
-       spin_unlock_irqrestore(&sr->sr_lock, flags);
-       return -1;
+       return set;
 }
 
 void mips_srs_free (int set)
 {
        struct shadow_registers *sr = &shadow_registers;
-       unsigned long flags;
 
-       spin_lock_irqsave(&sr->sr_lock, flags);
-       sr->sr_allocated &= ~(1 << set);
-       spin_unlock_irqrestore(&sr->sr_lock, flags);
+       clear_bit(set, &sr->sr_allocated);
 }
 
 static void *set_vi_srs_handler(int n, void *addr, int srs)