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

[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@xxxxxxxxxxxxx>


 arch/ia64/sn/kernel/xpc_main.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
--- a/arch/ia64/sn/kernel/xpc_main.c
+++ b/arch/ia64/sn/kernel/xpc_main.c
@@ -583,7 +583,7 @@ xpc_activate_partition(struct xpc_partit
 
 	pid = kernel_thread(xpc_activating, (void *) ((u64) partid), 0);
 
-	if (unlikely(pid <= 0)) {
+	if (unlikely(pid < 0)) {
 		spin_lock_irqsave(&part->act_lock, irq_flags);
 		part->act_state = XPC_P_INACTIVE;
 		XPC_SET_REASON(part, xpcCloneKThreadFailed, __LINE__);
-
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