On Fri, Jul 28, 2006 at 04:07:13PM -0400, [email protected] wrote:
> 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.
This is inconsistent with your assertion that pid 0 "is/should be valid"
above. If you want '0' to mean "not valid" then it's not a valid return
value from kernel_thread() (and arguably that's true, since pid 0 is
permanently allocated to the idle thread.)
I don't particularly care whether you decide to that returning pid 0 from
kernel_thread is valid or not, just that your two points above are at least
consistent with each other.
--
Russell King
Linux kernel 2.6 ARM Linux - http://www.arm.linux.org.uk/
maintainer of: 2.6 Serial core
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