[KJ] audit return code handling for kernel_thread [8/11]

[KJ] audit return code handling for kernel_thread [8/11]

[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>


 drivers/ieee1394/nodemgr.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)
--- a/drivers/ieee1394/nodemgr.c
+++ b/drivers/ieee1394/nodemgr.c
@@ -426,7 +426,8 @@ static ssize_t fw_set_rescan(struct bus_
 	 * something stupid and spawn this a lot of times, but that's
 	 * root's fault. */
 	if (state == 1)
-		kernel_thread(nodemgr_rescan_bus_thread, NULL, CLONE_KERNEL);
+		if (kernel_thread(nodemgr_rescan_bus_thread, NULL, CLONE_KERNEL) < 0)
+			printk(KERN_WARNING "Could not start 1394 bus rescan thread\n");
 
 	return count;
 }

Re: [KJ] audit return code handling for kernel_thread [8/11]

[Stefan Richter]

nhorman@tuxdriver.com wrote:
> --- a/drivers/ieee1394/nodemgr.c
> +++ b/drivers/ieee1394/nodemgr.c
> @@ -426,7 +426,8 @@ static ssize_t fw_set_rescan(struct bus_
>  	 * something stupid and spawn this a lot of times, but that's
>  	 * root's fault. */
>  	if (state == 1)
> -		kernel_thread(nodemgr_rescan_bus_thread, NULL, CLONE_KERNEL);
> +		if (kernel_thread(nodemgr_rescan_bus_thread, NULL, CLONE_KERNEL) < 0)
> +			printk(KERN_WARNING "Could not start 1394 bus rescan thread\n");
>  
>  	return count;
>  }

Thanks, but (a) we don't need the warnig and (b) we even don't need to 
spawn a thread at this point. This call to kernel_thread has been 
removed from git-ieee1394 and -mm earlier this month.
http://www.kernel.org/git/?p=linux/kernel/git/bcollins/linux1394-2.6.git;a=commitdiff_plain;h=40fd89cc54a8a67c81b5aa40b22c4f40b39e47b9
http://marc.theaimsgroup.com/?l=linux-mm-commits&m=115189722112717
-- 
Stefan Richter
-=====-=-==- -=== ===-=
http://arcgraph.de/sr/