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Subject[KJ] audit return code handling for kernel_thread [2/11]
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.


Signed-off-by: Neil Horman <>

arch/s390/mm/cmm.c | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)
--- a/arch/s390/mm/cmm.c
+++ b/arch/s390/mm/cmm.c
@@ -161,7 +161,10 @@ cmm_thread(void *dummy)
static void
- kernel_thread(cmm_thread, NULL, 0);
+ if (kernel_thread(cmm_thread, NULL, 0) < 0) {
+ printk(KERN_WARNING "Could not start cmm thread\n");
+ clear_bit(0,&cmm_thread_active);
+ }

static void
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