linux-kernel - [KJ] audit return code handling for kernel

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Date:	Fri, 28 Jul 2006 16:08:12 -0400
From:	nhorman@...driver.com
To:	kernel-janitors@...l.org, linux-kernel@...r.kernel.org,
	nhorman@...driver.com, paulus@...ibm.com
Subject: [KJ] audit return code handling for kernel_thread [10/11]

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.

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


 drivers/macintosh/therm_pm72.c |    4 ++++
 1 file changed, 4 insertions(+)
--- a/drivers/macintosh/therm_pm72.c
+++ b/drivers/macintosh/therm_pm72.c
@@ -1769,6 +1769,10 @@ static void start_control_loops(void)
 	init_completion(&ctrl_complete);
 
 	ctrl_task = kernel_thread(main_control_loop, NULL, SIGCHLD | CLONE_KERNEL);
+	if (ctrl_task < 0) {
+		printk(KERN_CRIT "could not start control thread\n");
+		ctrl_task = 0;
+	}
 }
 
 /*
-
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