[PATCH] ia64: perfmon fix

This patch allows users to set the PMC to their default value, even
though the value might conflict with the type of monitoring
session. This is fine because default values ensure the monitor is not
active.

arch/ia64/kernel/perfmon.c

@@ -1364,8 +1364,9 @@ pfm_write_pmcs(struct task_struct *task, pfm_context_t *ctx, void *arg, int coun
 	pfarg_reg_t tmp, *req = (pfarg_reg_t *)arg;
 	unsigned long value, reset_pmds;
 	unsigned int cnum, reg_flags, flags;
-	int i;
-	int ret = -EINVAL;
+	int is_monitor, is_counting;
+	int i, ret = -EINVAL;
+#define PFM_CHECK_PMC_PM(x, y, z) ((x)->ctx_fl_system ^ PMC_PM(y, z))
 
 	/* we don't quite support this right now */
 	if (task != current) return -EINVAL;
@@ -1384,6 +1385,9 @@ pfm_write_pmcs(struct task_struct *task, pfm_context_t *ctx, void *arg, int coun
 		reset_pmds = tmp.reg_reset_pmds[0];
 		flags      = 0;
 
+		is_counting = PMC_IS_COUNTING(cnum);
+		is_monitor  = PMC_IS_MONITOR(cnum);
+
 		/* 
 		 * we reject all non implemented PMC as well
 		 * as attempts to modify PMC[0-3] which are used
@@ -1394,21 +1398,19 @@ pfm_write_pmcs(struct task_struct *task, pfm_context_t *ctx, void *arg, int coun
 			goto error;
 		}
 		/*
-		 * A PMC used to configure monitors must be:
-		 * 	- system-wide session: privileged monitor
-		 * 	- per-task : user monitor
-		 * any other configuration is rejected.
+		 * If the PMC is a monitor, then if the value is not the default:
+		 * 	- system-wide session: PMCx.pm=1 (privileged monitor)
+		 * 	- per-task           : PMCx.pm=0 (user monitor)
 		 */
-		if (PMC_IS_MONITOR(cnum) || PMC_IS_COUNTING(cnum)) {
-			DBprintk(("pmc[%u].pm=%ld\n", cnum, PMC_PM(cnum, value))); 
-
-			if (ctx->ctx_fl_system ^ PMC_PM(cnum, value)) {
-				DBprintk(("pmc_pm=%ld fl_system=%d\n", PMC_PM(cnum, value), ctx->ctx_fl_system));
+		if ((is_monitor || is_counting) && value != PMC_DFL_VAL(i) && PFM_CHECK_PMC_PM(ctx, cnum, value)) {
+			DBprintk(("pmc%u pmc_pm=%ld fl_system=%d\n", 
+				cnum, 
+				PMC_PM(cnum, value), 
+				ctx->ctx_fl_system));
 			goto error;
 		}
-		}
 
-		if (PMC_IS_COUNTING(cnum)) {
+		if (is_counting) {
 			pfm_monitor_t *p = (pfm_monitor_t *)&value;
 			/*
 		 	 * enforce generation of overflow interrupt. Necessary on all
@@ -1471,7 +1473,7 @@ pfm_write_pmcs(struct task_struct *task, pfm_context_t *ctx, void *arg, int coun
 		 */
 		ctx->ctx_soft_pmds[cnum].flags = flags;
 
-		if (PMC_IS_COUNTING(cnum)) {
+		if (is_counting) {
 			ctx->ctx_soft_pmds[cnum].reset_pmds[0] = reset_pmds;
 
 			/* mark all PMDS to be accessed as used */