On Fri, May 9, 2014 at 3:14 PM, Lucas De Marchi
<lucas.demarchi@xxxxxxxxx> wrote:
> Since the beginning depmod just warned about dependency loops and upon
> creation of modules.dep{,.bin} it skipped the modules that were part of
> a loop. However just skipping the modules may come as a surprise to
> kernel module developers: they will need to try to load the module (or
> to pay attention to the log messages) to notice thavt the module has not
> been put in the index. Also, differently from module-init-tools we were
> not skipping modules that depend on modules with dependency loops,
> leading to a segfault in depmod.
>
> So this is a summary of the change in behavior with this patch:
>
> Loop 1)
> A -> B -> C -
> ^ |
> '------------
>
> Before:
> depmod: WARNING: found 3 modules in dependency cycles!
> depmod: WARNING: /tmp/test-kmod/lib/modules/3.14.2-1-ARCH/kernel/moduleB.ko in dependency cycle!
> depmod: WARNING: /tmp/test-kmod/lib/modules/3.14.2-1-ARCH/kernel/moduleC.ko in dependency cycle!
> depmod: WARNING: /tmp/test-kmod/lib/modules/3.14.2-1-ARCH/kernel/moduleA.ko in dependency cycle!
>
> return code: 0
>
> After:
> depmod: ERROR: Found 3 modules in dependency cycles!
> depmod: ERROR: /tmp/test-kmod/lib/modules/3.14.2-1-ARCH/kernel/moduleB.ko in dependency cycle!
> depmod: ERROR: /tmp/test-kmod/lib/modules/3.14.2-1-ARCH/kernel/moduleC.ko in dependency cycle!
> depmod: ERROR: /tmp/test-kmod/lib/modules/3.14.2-1-ARCH/kernel/moduleA.ko in dependency cycle!
>
> return code: 2
>
> Loop 2)
> A -> B -> C -
> ^ |
> '-------
>
> Before:
> depmod: WARNING: found 2 modules in dependency cycles!
> depmod: WARNING: /tmp/test-kmod//lib/modules/3.14.2-1-ARCH/kernel/moduleB.ko in dependency cycle!
> depmod: WARNING: /tmp/test-kmod//lib/modules/3.14.2-1-ARCH/kernel/moduleC.ko in dependency cycle!
> Segmentation fault (core dumped)
>
> After:
> depmod: ERROR: Found 2 modules in dependency cycles!
> depmod: ERROR: /tmp/test-kmod/lib/modules/3.14.2-1-ARCH/kernel/moduleB.ko in dependency cycle!
> depmod: ERROR: /tmp/test-kmod/lib/modules/3.14.2-1-ARCH/kernel/moduleC.ko in dependency cycle!
>
> return code: 2
>
> The segfault above could be fixed, but let's just fail everything
> because dependency cycles should be fixed in the modules rather than
> just be skipped in the index.
> ---
> tools/depmod.c | 55 +++++++++----------------------------------------------
> 1 file changed, 9 insertions(+), 46 deletions(-)
This is now applied. It's better to fail the upgrade than to provide
the user a broken setup, that maybe can't even boot successfully. The
old behavior can be achieved by just disabling the module in the
kernel config.
--
Lucas De Marchi
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