Re: Some -serious- BPF-related litmus tests

[Andrii Nakryiko]

On Tue, May 26, 2020 at 3:50 AM Akira Yokosawa <akiyks@xxxxxxxxx> wrote:
>
> On Mon, 25 May 2020 16:31:05 -0700, Andrii Nakryiko wrote:
> > On Mon, May 25, 2020 at 3:01 PM Akira Yokosawa <akiyks@xxxxxxxxx> wrote:
> >>
> [...]
> >> Yes, that should work.
> >
> > Ok, assigning to zero didn't work (it still complained about
> > uninitialized read), but using a separate int *lenFail to assign to
> > rLenPtr worked. Curiously, if I used rLenPtr = len1; in error case, it
> > actually takes a bit more time to verify.
> >
> > So I've converted everything else as you suggested. I compiled latest
> > herd7 and it doesn't produce any warnings. But it's also extremely
> > slow, compared to the herd7 that I get by default. Validating simple
> > 1p1c cases takes about 2.5x times longer (0.03s vs 0.07), but trying
> > to validate 2p1c case, which normally validates in 42s (unbounded) and
> > 110s (bounded), it took more than 20 minutes and hasn't finished,
> > before I gave up. So I don't know what's going on there...
>
> herdtools7 has recently been heavily restructured.
> On the performance regression, I must defer to Luc.
>
> Luc, do you have any idea?
>
> >
> > As for klitmus7, I managed to generate everything without warnings,
> > but couldn't make it build completely due to:
> >
> > $ make
> > make -C /lib/modules/5.6.13-01802-g938d64da97c6/build/
>
> So you are on Linux 5.6.x which requires cutting-edge klitmus7.
>

Right, so I retried with the klitmus7 built from sources:

$ klitmus7 -version

                                    7.55+01(dev)

Still can't compile, though task_struct problem went away, proc_ops
error is still present:

$ make
grep: /lib/modules/5.7.0-rc5-02014-gb16540c748e9/build/include/linux/proc_fs.h:
No such file or directory
make -C /lib/modules/5.7.0-rc5-02014-gb16540c748e9/build/
M=/home/andriin/local/linux-trees/tools/memory-model/mymodules modules
make[1]: Entering directory `/data/users/andriin/linux-build/fb-config'
make[2]: Entering directory `/data/users/andriin/linux-build/default-x86_64'
grep: /lib/modules/5.7.0-rc5-02014-gb16540c748e9/build/include/linux/proc_fs.h:
No such file or directory
  CC [M]  /home/andriin/local/linux-trees/tools/memory-model/mymodules/litmus000.o
/home/andriin/local/linux-trees/tools/memory-model/mymodules/litmus000.c:
In function âlitmus_initâ:
/home/andriin/local/linux-trees/tools/memory-model/mymodules/litmus000.c:621:67:
error: passing argument 4 of âproc_createâ from incompatible pointer
type [-Werror=incompatible-pointer-types]
   struct proc_dir_entry *litmus_pde =
proc_create("litmus",0,NULL,&litmus_proc_ops);

^~~~~~~~~~~~~~~~
In file included from
/home/andriin/local/linux-trees/tools/memory-model/mymodules/litmus000.c:15:
/data/users/andriin/linux/include/linux/proc_fs.h:79:24: note:
expected âconst struct proc_ops *â but argument is of type âconst
struct file_operations *â
 struct proc_dir_entry *proc_create(const char *name, umode_t mode,
struct proc_dir_entry *parent, const struct proc_ops *proc_ops);
                        ^~~~~~~~~~~
cc1: some warnings being treated as errors
make[3]: *** [/home/andriin/local/linux-trees/tools/memory-model/mymodules/litmus000.o]
Error 1
make[2]: *** [/home/andriin/local/linux-trees/tools/memory-model/mymodules]
Error 2
make[2]: Leaving directory `/data/users/andriin/linux-build/default-x86_64'
make[1]: *** [sub-make] Error 2
make[1]: Leaving directory `/data/users/andriin/linux-build/fb-config'
make: *** [all] Error 2

Don't know if I'm missing some headers or whatever.

> > M=/home/andriin/local/linux-trees/tools/memory-model/mymodules modules
> > make[1]: Entering directory `/data/users/andriin/linux-build/fb-config'
> > make[2]: Entering directory `/data/users/andriin/linux-build/default-x86_64'
> >   CC [M]  /home/andriin/local/linux-trees/tools/memory-model/mymodules/litmus000.o
> > /home/andriin/local/linux-trees/tools/memory-model/mymodules/litmus000.c:
> > In function âzyvaâ:
> > /home/andriin/local/linux-trees/tools/memory-model/mymodules/litmus000.c:507:12:
> > warning: ISO C90 forbids variable length array âthâ [-Wvla]
> >      struct task_struct *th[nth];
> >             ^~~~~~~~~~~
> > /home/andriin/local/linux-trees/tools/memory-model/mymodules/litmus000.c:
> > In function âlitmus_initâ:
> > /home/andriin/local/linux-trees/tools/memory-model/mymodules/litmus000.c:605:67:
> > error: passing argument 4 of âproc_createâ from incompatible pointer
> > type [-Werror=incompatible-pointer-types]
> >    struct proc_dir_entry *litmus_pde =
> > proc_create("litmus",0,NULL,&litmus_proc_fops);
> >
> > ^~~~~~~~~~~~~~~~~
> > In file included from
> > /home/andriin/local/linux-trees/tools/memory-model/mymodules/litmus000.c:15:
> > /data/users/andriin/linux-fb/include/linux/proc_fs.h:64:24: note:
> > expected âconst struct proc_ops *â but argument is of type âconst
> > struct file_operations *â
> >  struct proc_dir_entry *proc_create(const char *name, umode_t mode,
> > struct proc_dir_entry *parent, const struct proc_ops *proc_ops);
> >                         ^~~~~~~~~~~
> > cc1: some warnings being treated as errors
> > make[3]: *** [/home/andriin/local/linux-trees/tools/memory-model/mymodules/litmus000.o]
> > Error 1
> > make[2]: *** [/home/andriin/local/linux-trees/tools/memory-model/mymodules]
> > Error 2
> > make[2]: Leaving directory `/data/users/andriin/linux-build/default-x86_64'
> > make[1]: *** [sub-make] Error 2
> > make[1]: Leaving directory `/data/users/andriin/linux-build/fb-config'
> > make: *** [all] Error 2
> >
>
> These errors suggest the klitmus7 you used is version 7.52 or some such.
> You said you have built herd7 from the source.  Have you also built klitmus7?

I did, but it wasn't in the PATH. I retried with latest klitmus7 and
still run into problems.

>
> The up-to-date klitmus7 should generate code compatible with Linux 5.6.x.
>
> Could you try with the latest one?
>
>         Thanks, Akira
>
> >
> > But at least it doesn't complain about atomic_t anymore. So anyways,
> > I'm going to post updated litmus tests separately from BPF ringbuf
> > patches, because Documentation/litmus-tests is not yet present in
> > bpf-next.
> >
> >>
> >> You can find a basic introduction of klitmus7 in tools/memory-model/README.
> >>
> >>         Thanks, Akira
> >>
> >>>
> >>>>
> >>>> Please note that if you are on Linux 5.6 (or later), you need an up-to-date
> >>>> klitmus7 due to a change in kernel API.
> >>>>
> >>>> Any question is welcome!
> >>>>
> >>>>         Thanks, Akira
> >>>>
> >
> > [...]
> >
>