Messages in this thread | | | Date | Sat, 29 Jul 2006 09:55:13 -0400 | From | Neil Horman <> | Subject | Re: [KJ] audit return code handling for kernel_thread [2/11] |
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On Sat, Jul 29, 2006 at 09:14:19AM -0400, Neil Horman wrote: > On Sat, Jul 29, 2006 at 10:37:04AM +0100, Russell King wrote: > > On Fri, Jul 28, 2006 at 04:07:13PM -0400, nhorman@tuxdriver.com 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.) > > > No its, not, but I can see how my comments might be ambiguous. I want zero to be > a valid return code, since we never actually return zero, but we certainly could > if we wanted to. Note that kernel_thread returns an int (not an unsigned int), > and as such assuming that a non-zero return code implies success ignores the > fact that kernel_thread can return a negative value, which indicates failure. > This is what I found, and what my patch fixes. > > > 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. > > > My comments in (2) should be made more clear by changing "assume a non-zero > return was success" to "assume a negative return was success". This is what my > patch fixes. > > Thanks & Regards > Neil >
P.S. - Sorry, Russell, et al. for the double post. My network link went out and I accendentally sent two replies to your note
Neil
> > -- > > Russell King > > Linux kernel 2.6 ARM Linux - http://www.arm.linux.org.uk/ > > maintainer of: 2.6 Serial core > - > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/ - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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