powerpc/spufs: sputrace: Only enable logging on open(), prevent multiple openers

Currently, sputrace will start logging to the event buffer before the
log buffer has been open()ed. This results in a heap of "lost samples"
warnings if the sputrace file hasn't yet been opened.

Since the buffer is reset on open() anyway, there's no need to enable
logging when no-one has opened the log.

Because open clears the log, make it return EBUSY for mutliple open
calls.

Signed-off-by: Jeremy Kerr <jk@ozlabs.org>

1 files changed, 29 insertions, 3 deletions

diff --git a/arch/powerpc/platforms/cell/spufs/sputrace.c b/arch/powerpc/platforms/cell/spufs/sputrace.c
index 92d20e993ede..50cae0cf0988 100644
--- a/arch/powerpc/platforms/cell/spufs/sputrace.c
+++ b/arch/powerpc/platforms/cell/spufs/sputrace.c
@@ -40,6 +40,7 @@ static DECLARE_WAIT_QUEUE_HEAD(sputrace_wait);
 static ktime_t sputrace_start;
 static unsigned long sputrace_head, sputrace_tail;
 static struct sputrace *sputrace_log;
+static int sputrace_logging;
 
 static int sputrace_used(void)
 {
@@ -109,24 +110,49 @@ static ssize_t sputrace_read(struct file *file, char __user *buf,
 
 static int sputrace_open(struct inode *inode, struct file *file)
 {
+        int rc;
+
         spin_lock(&sputrace_lock);
+        if (sputrace_logging) {
+                rc = -EBUSY;
+                goto out;
+        }
+
+        sputrace_logging = 1;
         sputrace_head = sputrace_tail = 0;
         sputrace_start = ktime_get();
+        rc = 0;
+
+out:
         spin_unlock(&sputrace_lock);
+        return rc;
+}
 
+static int sputrace_release(struct inode *inode, struct file *file)
+{
+        spin_lock(&sputrace_lock);
+        sputrace_logging = 0;
+        spin_unlock(&sputrace_lock);
         return 0;
 }
 
 static const struct file_operations sputrace_fops = {
-        .owner  = THIS_MODULE,
-        .open   = sputrace_open,
-        .read   = sputrace_read,
+        .owner   = THIS_MODULE,
+        .open    = sputrace_open,
+        .read    = sputrace_read,
+        .release = sputrace_release,
 };
 
 static void sputrace_log_item(const char *name, struct spu_context *ctx,
                 struct spu *spu)
 {
         spin_lock(&sputrace_lock);
+
+        if (!sputrace_logging) {
+                spin_unlock(&sputrace_lock);
+                return;
+        }
+
         if (sputrace_avail() > 1) {
                 struct sputrace *t = sputrace_log + sputrace_head;