[PATCH] powerpc/opal_elog: Handle multiple writes to ack attribute

["Aneesh Kumar K.V" <aneesh.kumar@linux.ibm.com>]

Even though we use self removing sysfs helper, we still need
to make sure we do the final kobject delete conditionally.
sysfs_remove_file_self() will handle parallel calls to remove
the sysfs attribute file and returns true only in the caller
that removed the attribute file. The other parallel callers
are returned false. Do the final kobject delete checking
the return value of sysfs_remove_file_self().

Cc: Mahesh Salgaonkar <mahesh@linux.ibm.com>
Cc: Oliver O'Halloran <oohall@gmail.com>
Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
---
 arch/powerpc/platforms/powernv/opal-elog.c | 11 ++++++++---
 1 file changed, 8 insertions(+), 3 deletions(-)

diff --git a/arch/powerpc/platforms/powernv/opal-elog.c b/arch/powerpc/platforms/powernv/opal-elog.c
index 5e33b1fc67c2..37b380eef41a 100644
--- a/arch/powerpc/platforms/powernv/opal-elog.c
+++ b/arch/powerpc/platforms/powernv/opal-elog.c
@@ -72,9 +72,14 @@ static ssize_t elog_ack_store(struct elog_obj *elog_obj,
 			      const char *buf,
 			      size_t count)
 {
-	opal_send_ack_elog(elog_obj->id);
-	sysfs_remove_file_self(&elog_obj->kobj, &attr->attr);
-	kobject_put(&elog_obj->kobj);
+	/*
+	 * Try to self remove this attribute. If we are successful,
+	 * delete the kobject itself.
+	 */
+	if (sysfs_remove_file_self(&elog_obj->kobj, &attr->attr)) {
+		opal_send_ack_elog(elog_obj->id);
+		kobject_put(&elog_obj->kobj);
+	}
 	return count;
 }
 
-- 
2.26.2