[PATCH] ARM: 2664/2: add support for atomic ops on pre-ARMv6 SMP systems

[GitHub/mt8127/android_kernel_alcatel_ttab.git] / arch / arm / kernel / entry-armv.S

diff --git a/arch/arm/kernel/entry-armv.S b/arch/arm/kernel/entry-armv.S
index 4eb36155dc93fa169b8853a75cd746566a31da49..e14278d59882367dc579f1dabeb5f2d191772ee2 100644 (file)
--- a/arch/arm/kernel/entry-armv.S
+++ b/arch/arm/kernel/entry-armv.S
@@ -269,7 +269,7 @@ __pabt_svc:
        add     r5, sp, #S_PC
        ldmia   r7, {r2 - r4}                   @ Get USR pc, cpsr
 
-#if __LINUX_ARM_ARCH__ < 6
+#if __LINUX_ARM_ARCH__ < 6 && !defined(CONFIG_NEEDS_SYSCALL_FOR_CMPXCHG)
        @ make sure our user space atomic helper is aborted
        cmp     r2, #VIRT_OFFSET
        bichs   r3, r3, #PSR_Z_BIT
@@ -616,11 +616,17 @@ __kuser_helper_start:
 
 __kuser_cmpxchg:                               @ 0xffff0fc0
 
-#if __LINUX_ARM_ARCH__ < 6
+#if defined(CONFIG_NEEDS_SYSCALL_FOR_CMPXCHG)
 
-#ifdef CONFIG_SMP  /* sanity check */
-#error "CONFIG_SMP on a machine supporting pre-ARMv6 processors?"
-#endif
+       /*
+        * Poor you.  No fast solution possible...
+        * The kernel itself must perform the operation.
+        * A special ghost syscall is used for that (see traps.c).
+        */
+       swi     #0x9ffff0
+       mov     pc, lr
+
+#elif __LINUX_ARM_ARCH__ < 6
 
        /*
         * Theory of operation: