[PATCH] fix oprofile on x86 > 1 counter

Without this we have a choice between dropping lots of counter events
for counters > 0, or getting dazed and confused.  This brings it inline
with the 2.4 module code.  Tested on my 2-way.

Also fix a typo from Steven Cole, and remove some unnecessary code

arch/alpha/oprofile/op_model_ev4.c

@@ -34,7 +34,7 @@ ev4_reg_setup(struct op_register_config *reg,
 	   for these "disabled" counter overflows are ignored by the
 	   interrupt handler.
 
-	   This is most irritating, becuase the hardware *can* enable and
+	   This is most irritating, because the hardware *can* enable and
 	   disable the interrupts for these counters independently, but the
 	   wrperfmon interface doesn't allow it.  */
 

arch/i386/oprofile/op_model_athlon.c

@@ -104,10 +104,11 @@ static int athlon_check_ctrs(unsigned int const cpu,
 		if (CTR_OVERFLOWED(low)) {
 			oprofile_add_sample(eip, is_kernel, i, cpu);
 			CTR_WRITE(reset_value[i], msrs, i);
-			return 1;
 		}
 	}
-	return 0;
+
+	/* See op_model_ppro.c */
+	return 1;
 }
 
  

arch/i386/oprofile/op_model_p4.c

@@ -608,13 +608,14 @@ static int p4_check_ctrs(unsigned int const cpu,
  			CTR_WRITE(reset_value[i], real);
 			/* P4 quirk: you have to re-unmask the apic vector */
 			apic_write(APIC_LVTPC, apic_read(APIC_LVTPC) & ~APIC_LVT_MASKED);
-			return 1;
 		}
 	}
 
 	/* P4 quirk: you have to re-unmask the apic vector */
 	apic_write(APIC_LVTPC, apic_read(APIC_LVTPC) & ~APIC_LVT_MASKED);
-	return 0;
+
+	/* See op_model_ppro.c */
+	return 1;
 }
 
 

arch/i386/oprofile/op_model_ppro.c

@@ -98,10 +98,17 @@ static int ppro_check_ctrs(unsigned int const cpu,
 		if (CTR_OVERFLOWED(low)) {
 			oprofile_add_sample(eip, is_kernel, i, cpu);
 			CTR_WRITE(reset_value[i], msrs, i);
-			return 1;
 		}
 	}
-	return 0;
+
+	/* We can't work out if we really handled an interrupt. We
+	 * might have caught a *second* counter just after overflowing
+	 * the interrupt for this counter then arrives
+	 * and we don't find a counter that's overflowed, so we
+	 * would return 0 and get dazed + confused. Instead we always
+	 * assume we found an overflow. This sucks.
+	 */
+	return 1;
 }
 
  

drivers/oprofile/cpu_buffer.c

@@ -85,9 +85,6 @@ static unsigned long nr_available_slots(struct oprofile_cpu_buffer const * b)
 	unsigned long head = b->head_pos;
 	unsigned long tail = b->tail_pos;
 
-	if (tail == head)
-		return b->buffer_size;
-
 	if (tail > head)
 		return tail - head;