[KJ] audit return code handling for kernel_thread [3/11]

[KJ] audit return code handling for kernel_thread [3/11]

[nhorman]

Audit/Cleanup of kernel_thread calls, specifically checking of return codes.
    Problems seemed to fall into 3 main categories:
    
    1) callers of kernel_thread were inconsistent about meaning of a zero return
    code.  Some callers considered a zero return code to mean success, others took
    it to mean failure.  a zero return code, while not actually possible in the
    current implementation, should be considered a success (pid 0 is/should be
    valid). fixed all callers to treat zero return as success
    
    2) caller of kernel_thread saved return code of kernel_thread for later use
    without ever checking its value.  Callers who did this tended to assume a
    non-zero return was success, and would often wait for a completion queue to be
    woken up, implying that an error (negative return code) from kernel_thread could
    lead to deadlock.  Repaired by checking return code at call time, and setting
    saved return code to zero in the event of an error.
    
    3) callers of kernel_thread never bothered to check the return code at all.
    This can lead to seemingly unrelated errors later in execution.  Fixed by
    checking return code at call time and printing a warning message on failure.

Regards
Neil
    
Signed-off-by: Neil Horman <nhorman@tuxdriver.com>


 core.c |    6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)
--- a/net/bluetooth/rfcomm/core.c
+++ b/net/bluetooth/rfcomm/core.c
@@ -2052,11 +2052,15 @@ static CLASS_ATTR(rfcomm_dlc, S_IRUGO, r
 /* ---- Initialization ---- */
 static int __init rfcomm_init(void)
 {
+	int ret;
 	l2cap_load();
 
 	hci_register_cb(&rfcomm_cb);
 
-	kernel_thread(rfcomm_run, NULL, CLONE_KERNEL);
+	ret = kernel_thread(rfcomm_run, NULL, CLONE_KERNEL);
+	
+	if (ret < 0)
+		return ret;
 
 	class_create_file(bt_class, &class_attr_rfcomm_dlc);