linux-kernel - Re: [PATCH] perf bench numa: Fix for loop in do

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Message-ID: <b2a9b1eb-e8a4-31c2-db33-5fa8ecc862da@arm.com>
Date:   Thu, 30 Mar 2023 09:31:31 +0100
From:   James Clark <james.clark@....com>
To:     Andreas Herrmann <aherrmann@...e.de>,
        Arnaldo Carvalho de Melo <acme@...nel.org>
Cc:     linux-kernel@...r.kernel.org, linux-perf-users@...r.kernel.org
Subject: Re: [PATCH] perf bench numa: Fix for loop in do_work



On 30/03/2023 08:42, Andreas Herrmann wrote:
> j is of type int and start/end are of type long. Thus j might become
> negative and cause segfault in access_data(). Fix it by using long for
> j as well.
> 
> Signed-off-by: Andreas Herrmann <aherrmann@...e.de>
> ---
>  tools/perf/bench/numa.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> Example of segfault (with 6.3.0-rc4) is:
> 
> # ./perf bench numa mem -d -m -p 2 -t 12 -P 25425
> ...
>  threads initialized in 6.052135 seconds.
>  #
> perf: bench/numa.c:1654: __bench_numa: Assertion `!(!(((wait_stat) & 0x7f) == 0))' failed.
> Aborted (core dumped)
> # dmesg | grep segfault
> [78812.711311] thread 1/3[43215]: segfault at 7f07936c9ec0 ip 00000000004ab6d0 sp 00007f0acb1f9cb0 error 4
> [78812.711309] thread 1/9[43221]: segfault at 7f08bda71a70 ip 00000000004ab6d0 sp 00007f0ac81f3cb0 error 4
> [78812.711316] thread 1/4[43216]: segfault at 7f07ccf76a08 ip 00000000004ab6d0 sp 00007f0aca9f8cb0 error 4
> [78812.711325] thread 1/2[43214]: segfault at 7f08be2f44b0 ip 00000000004ab6d0 sp 00007f0acb9facb0 error 4
> [78812.711328] thread 1/8[43220]: segfault at 7f06d3096b20 ip 00000000004ab6d0 sp 00007f0ac89f4cb0 error 4
> [78812.711345] thread 1/6[43218]: segfault at 7f0774b46a18 ip 00000000004ab6d0 sp 00007f0ac99f6cb0 error 4 in perf[400000+caa000] likely on CPU 6 (core 8, socket 0)
> [78812.711366] thread 0/0[43224]: segfault at 7f08a936b130 ip 00000000004ab6d0 sp 00007f0acc9fccb0 error 4 in perf[400000+caa000] likely on CPU 1 (core 1, socket 0)
> 
> diff --git a/tools/perf/bench/numa.c b/tools/perf/bench/numa.c
> index 9717c6c17433..1fbd7c947abc 100644
> --- a/tools/perf/bench/numa.c
> +++ b/tools/perf/bench/numa.c
> @@ -847,7 +847,7 @@ static u64 do_work(u8 *__data, long bytes, int nr, int nr_max, int loop, u64 val
>  
>  	if (g->p.data_rand_walk) {
>  		u32 lfsr = nr + loop + val;
> -		int j;
> +		long j;
>  
>  		for (i = 0; i < words/1024; i++) {
>  			long start, end;

Reviewed-by: James Clark <james.clark@....com>