netdev - Re: concurrent rhashtable test failure

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Message-ID: <20161026073337.GM5640@orbyte.nwl.cc>
Date:   Wed, 26 Oct 2016 09:33:37 +0200
From:   Phil Sutter <phil@....cc>
To:     Geert Uytterhoeven <geert@...ux-m68k.org>
Cc:     Thomas Graf <tgraf@...g.ch>,
        Herbert Xu <herbert@...dor.apana.org.au>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        linux-m68k <linux-m68k@...ts.linux-m68k.org>
Subject: Re: concurrent rhashtable test failure

Hi Geert,

On Mon, Oct 24, 2016 at 02:11:32PM +0200, Geert Uytterhoeven wrote:
> On m68k/ARAnyM, test_rhashtable fails with:
> 
>     Test failed: thread 0 returned: -4
> 
> (-4 = -EINTR)

How reproducible is this? I wonder why out of the ten threads only the
first one fails.

> I traced this back to your commit f4a3e90ba5739cfd ("rhashtable-test: extend
> to test concurrency"), which added that part of the test.
> 
> Diff of the test output between the failing commit and its parent:
> 
>  Running rhashtable test nelem=8, max_size=65536, shrinking=0
>  Test 00:
>    Adding 50000 keys
>    Traversal complete: counted=50000, nelems=50000, entries=50000, table-jumps=0
>    Traversal complete: counted=50000, nelems=50000, entries=50000, table-jumps=0
>    Deleting 50000 keys
> -  Duration of test: 1029960000 ns
> +  Duration of test: 990000000 ns
>  Test 01:
>    Adding 50000 keys
>    Traversal complete: counted=50000, nelems=50000, entries=50000, table-jumps=0
>    Traversal complete: counted=50000, nelems=50000, entries=50000, table-jumps=0
>    Deleting 50000 keys
> -  Duration of test: 990000000 ns
> +  Duration of test: 720000000 ns
>  Test 02:
>    Adding 50000 keys
>    Traversal complete: counted=50000, nelems=50000, entries=50000, table-jumps=0
>    Traversal complete: counted=50000, nelems=50000, entries=50000, table-jumps=0
>    Deleting 50000 keys
> -  Duration of test: 1130000000 ns
> +  Duration of test: 700000000 ns
>  Test 03:
>    Adding 50000 keys
>    Traversal complete: counted=50000, nelems=50000, entries=50000, table-jumps=0
>    Traversal complete: counted=50000, nelems=50000, entries=50000, table-jumps=0
>    Deleting 50000 keys
> -  Duration of test: 1080000000 ns
> -Average test time: 1057490000
> +  Duration of test: 700000000 ns
> +Average test time: 777500000
> +Testing concurrent rhashtable access from 10 threads
> +Test failed: thread 0 returned: -4
> +Started 10 threads, 1 failed
> 
> Do you have any clue?

Not really, I merely implemented the test.

Thanks, Phil