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SubjectRe: [KJ] audit return code handling for kernel_thread [1/11]
On Sat, Jul 29, 2006 at 09:49:01AM +1000, Nick Piggin wrote:
> nhorman@tuxdriver.com wrote:
> >Audit/Cleanup of kernel_thread calls, specifically checking of return
> >codes.
> > Problems seemed to fall into 3 main categories:
> >
>
> Thanks for doing this. Nitpick: this should be all one patch, or at most 3
> patches (then each of the below 3 items would become individual changelogs).
>
You're welcome. I specifically split it into multiple little patches, as each file has a
different maintainer, but if the consensus is for one patch (or three), so be it, I'll do
that in the future.

> Each patch should have a unique changelog, each should have a unique subject
> (sans the sequence number).
>
> cc'ing Andrew is also a good idea, if you want them to get merged ;)
>
I can do that :)

> One coding style comment:
> if (...)
> multi line
> statement
>
> Could use braces around the outermost if statement, for clarity.
>
If you ack this, I'll post a follow on patch to clean that up next week. I've already
received a suggestion to use the same failure to start thread warning message to
save string table space, so I've got some extra clean up to do anyway.

Regards
Neil

>
> > 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.
>
> --
> SUSE Labs, Novell Inc.
> Send instant messages to your online friends http://au.messenger.yahoo.com

--
/***************************************************
*Neil Horman
*Software Engineer
*gpg keyid: 1024D / 0x92A74FA1 - http://pgp.mit.edu
***************************************************/
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