[PATCH] alpha fp-emu vs module refcounting

From: Ivan Kokshaysky <ink@jurassic.park.msu.ru>

This allows building the math-emu code as a module only when
CONFIG_SMP is not set. The fp trap handler cannot be preempted
on a single-CPU (as CONFIG_PREEMPT is not going to be supported
on alpha), so the module can be safely unloaded at any time.

arch/alpha/Kconfig

@@ -626,8 +626,8 @@ config DEBUG_KERNEL
 	  identify kernel problems.
 
 config MATHEMU
-	tristate "Kernel FP software completion" if DEBUG_KERNEL
-	default y if !DEBUG_KERNEL
+	tristate "Kernel FP software completion" if DEBUG_KERNEL && !SMP
+	default y if !DEBUG_KERNEL || SMP
 	help
 	  This option is required for IEEE compliant floating point arithmetic
 	  on the Alpha. The only time you would ever not say Y is to say M in

arch/alpha/math-emu/Makefile

@@ -4,4 +4,6 @@
 
 EXTRA_CFLAGS := -w
 
-obj-$(CONFIG_MATHEMU) += math.o qrnnd.o
+obj-$(CONFIG_MATHEMU) += math-emu.o
+
+math-emu-objs := math.o qrnnd.o

arch/alpha/math-emu/math.c

@@ -106,8 +106,6 @@ alpha_fp_emul (unsigned long pc)
 	__u32 insn;
 	long si_code;
 
-	MOD_INC_USE_COUNT;
-
 	get_user(insn, (__u32*)pc);
 	fc     = (insn >>  0) & 0x1f;	/* destination register */
 	fb     = (insn >> 16) & 0x1f;
@@ -320,7 +318,6 @@ alpha_fp_emul (unsigned long pc)
 			if (_fex & IEEE_TRAP_ENABLE_INV) si_code = FPE_FLTINV;
 		}
 
-		MOD_DEC_USE_COUNT;
 		return si_code;
 	}
 
@@ -328,13 +325,11 @@ alpha_fp_emul (unsigned long pc)
 	   requires that the result *always* be written... so we do the write
 	   immediately after the operations above.  */
 
-	MOD_DEC_USE_COUNT;
 	return 0;
 
 bad_insn:
 	printk(KERN_ERR "alpha_fp_emul: Invalid FP insn %#x at %#lx\n",
 	       insn, pc);
-	MOD_DEC_USE_COUNT;
 	return -1;
 }
 
@@ -344,8 +339,6 @@ alpha_fp_emul_imprecise (struct pt_regs *regs, unsigned long write_mask)
 	unsigned long trigger_pc = regs->pc - 4;
 	unsigned long insn, opcode, rc, si_code = 0;
 
-	MOD_INC_USE_COUNT;
-
 	/*
 	 * Turn off the bits corresponding to registers that are the
 	 * target of instructions that set bits in the exception
@@ -403,6 +396,5 @@ alpha_fp_emul_imprecise (struct pt_regs *regs, unsigned long write_mask)
 	}
 
 egress:
-	MOD_DEC_USE_COUNT;
 	return si_code;
 }