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

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

1 files changed, 18 insertions, 23 deletions

diff --git a/arch/mips/kernel/traps.c b/arch/mips/kernel/traps.c
index 61efc61c45e2..081e6ed5bb62 100644
--- 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)