Re: Some -serious- BPF-related litmus tests
From: Akira Yokosawa
Date: Tue May 26 2020 - 06:50:56 EST
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.
> M=/home/andriin/local/linux-trees/tools/memory-model/mymodules modules
> make: Entering directory `/data/users/andriin/linux-build/fb-config'
> make: Entering directory `/data/users/andriin/linux-build/default-x86_64'
> CC [M] /home/andriin/local/linux-trees/tools/memory-model/mymodules/litmus000.o
> In function âzyvaâ:
> warning: ISO C90 forbids variable length array âthâ [-Wvla]
> struct task_struct *th[nth];
> In function âlitmus_initâ:
> error: passing argument 4 of âproc_createâ from incompatible pointer
> type [-Werror=incompatible-pointer-types]
> struct proc_dir_entry *litmus_pde =
> In file included from
> /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: *** [/home/andriin/local/linux-trees/tools/memory-model/mymodules/litmus000.o]
> Error 1
> make: *** [/home/andriin/local/linux-trees/tools/memory-model/mymodules]
> Error 2
> make: Leaving directory `/data/users/andriin/linux-build/default-x86_64'
> make: *** [sub-make] Error 2
> make: 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?
The up-to-date klitmus7 should generate code compatible with Linux 5.6.x.
Could you try with the latest one?
> 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
>> 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