1 files changed, 12 insertions, 11 deletions

diff --git a/arch/powerpc/platforms/pseries/dtl.c b/arch/powerpc/platforms/pseries/dtl.c
index ab5de985a787..2b87480f2837 100644
--- a/arch/powerpc/platforms/pseries/dtl.c
+++ b/arch/powerpc/platforms/pseries/dtl.c
@@ -27,13 +27,7 @@ struct dtl {
 };
 static DEFINE_PER_CPU(struct dtl, cpu_dtl);
 
-/*
- * Dispatch trace log event mask:
- * 0x7: 0x1: voluntary virtual processor waits
- *      0x2: time-slice preempts
- *      0x4: virtual partition memory page faults
- */
-static u8 dtl_event_mask = 0x7;
+static u8 dtl_event_mask = DTL_LOG_ALL;
 
 
 /*
@@ -48,7 +42,6 @@ struct dtl_ring {
 	struct dtl_entry *write_ptr;
 	struct dtl_entry *buf;
 	struct dtl_entry *buf_end;
-	u8	saved_dtl_mask;
 };
 
 static DEFINE_PER_CPU(struct dtl_ring, dtl_rings);
@@ -98,7 +91,6 @@ static int dtl_start(struct dtl *dtl)
 	dtlr->write_ptr = dtl->buf;
 
 	/* enable event logging */
-	dtlr->saved_dtl_mask = lppaca_of(dtl->cpu).dtl_enable_mask;
 	lppaca_of(dtl->cpu).dtl_enable_mask |= dtl_event_mask;
 
 	dtl_consumer = consume_dtle;
@@ -116,7 +108,7 @@ static void dtl_stop(struct dtl *dtl)
 	dtlr->buf = NULL;
 
 	/* restore dtl_enable_mask */
-	lppaca_of(dtl->cpu).dtl_enable_mask = dtlr->saved_dtl_mask;
+	lppaca_of(dtl->cpu).dtl_enable_mask = DTL_LOG_PREEMPT;
 
 	if (atomic_dec_and_test(&dtl_count))
 		dtl_consumer = NULL;
@@ -188,11 +180,16 @@ static int dtl_enable(struct dtl *dtl)
 	if (dtl->buf)
 		return -EBUSY;
 
+	/* ensure there are no other conflicting dtl users */
+	if (!read_trylock(&dtl_access_lock))
+		return -EBUSY;
+
 	n_entries = dtl_buf_entries;
 	buf = kmem_cache_alloc_node(dtl_cache, GFP_KERNEL, cpu_to_node(dtl->cpu));
 	if (!buf) {
 		printk(KERN_WARNING "%s: buffer alloc failed for cpu %d\n",
 				__func__, dtl->cpu);
+		read_unlock(&dtl_access_lock);
 		return -ENOMEM;
 	}
 
@@ -209,8 +206,11 @@ static int dtl_enable(struct dtl *dtl)
 	}
 	spin_unlock(&dtl->lock);
 
-	if (rc)
+	if (rc) {
+		read_unlock(&dtl_access_lock);
 		kmem_cache_free(dtl_cache, buf);
+	}
+
 	return rc;
 }
 
@@ -222,6 +222,7 @@ static void dtl_disable(struct dtl *dtl)
 	dtl->buf = NULL;
 	dtl->buf_entries = 0;
 	spin_unlock(&dtl->lock);
+	read_unlock(&dtl_access_lock);
 }
 
 /* file interface */