Subject: [PATCH] powerpc/powernv/dump: Handle multiple writes to ack attribute

From: Vasant Hegde <[email-masked]>
Date: Sat, 17 Oct 2020 22:12:36 +0530

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: Aneesh Kumar K.V <[email-masked]>
Cc: Mahesh Salgaonkar <[email-masked]>
Signed-off-by: Vasant Hegde <[email-masked]>
---
 arch/powerpc/platforms/powernv/opal-dump.c | 11 ++++++++---
 1 file changed, 8 insertions(+), 3 deletions(-)

diff --git a/arch/powerpc/platforms/powernv/opal-dump.c b/arch/powerpc/platforms/powernv/opal-dump.c
index 0e6693bacb7e..00c5a59d82d9 100644
--- a/arch/powerpc/platforms/powernv/opal-dump.c
+++ b/arch/powerpc/platforms/powernv/opal-dump.c
@@ -88,9 +88,14 @@ static ssize_t dump_ack_store(struct dump_obj *dump_obj,
 			      const char *buf,
 			      size_t count)
 {
-	dump_send_ack(dump_obj->id);
-	sysfs_remove_file_self(&dump_obj->kobj, &attr->attr);
-	kobject_put(&dump_obj->kobj);
+	/*
+	 * Try to self remove this attribute. If we are successful,
+	 * delete the kobject itself.
+	 */
+	if (sysfs_remove_file_self(&dump_obj->kobj, &attr->attr)) {
+		dump_send_ack(dump_obj->id);
+		kobject_put(&dump_obj->kobj);
+	}
 	return count;
 }
 
-- 
2.26.2