linux-kernel - Re: Some -serious- BPF-related litmus tests

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Date:   Wed, 27 May 2020 07:23:24 +0900
From:   Akira Yokosawa <akiyks@...il.com>
To:     Andrii Nakryiko <andrii.nakryiko@...il.com>
Cc:     luc.maranget@...ia.fr, Andrii Nakryiko <andriin@...com>,
        "Paul E . McKenney" <paulmck@...nel.org>,
        Alan Stern <stern@...land.harvard.edu>,
        Peter Zijlstra <peterz@...radead.org>, parri.andrea@...il.com,
        will@...nel.org, Boqun Feng <boqun.feng@...il.com>,
        npiggin@...il.com, dhowells@...hat.com, j.alglave@....ac.uk,
        dlustig@...dia.com, Joel Fernandes <joel@...lfernandes.org>,
        open list <linux-kernel@...r.kernel.org>,
        linux-arch@...r.kernel.org
Subject: Re: Some -serious- BPF-related litmus tests

On Tue, 26 May 2020 13:15:49 -0700, Andrii Nakryiko wrote:
> On Tue, May 26, 2020 at 3:50 AM Akira Yokosawa <akiyks@...il.com> 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@...il.com> 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

Hmm, have you installed kernel-headers on your system?
You are now on Linux 5.7-rc5 based system...

        Thanks, Akira

> 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 ‘litmus_init’:
> /home/andriin/local/linux-trees/tools/memory-model/mymodules/litmus000.c:621:67:
> error: passing argument 4 of ‘proc_create’ 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 ‘const struct proc_ops *’ but argument is of type ‘const
> struct file_operations *’
>  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 ‘zyva’:
>>> /home/andriin/local/linux-trees/tools/memory-model/mymodules/litmus000.c:507:12:
>>> warning: ISO C90 forbids variable length array ‘th’ [-Wvla]
>>>      struct task_struct *th[nth];
>>>             ^~~~~~~~~~~
>>> /home/andriin/local/linux-trees/tools/memory-model/mymodules/litmus000.c:
>>> In function ‘litmus_init’:
>>> /home/andriin/local/linux-trees/tools/memory-model/mymodules/litmus000.c:605:67:
>>> error: passing argument 4 of ‘proc_create’ 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 ‘const struct proc_ops *’ but argument is of type ‘const
>>> struct file_operations *’
>>>  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
>>>>>>
>>>
>>> [...]
>>>
>>