linux-kernel - Re: [Patch v2] lib: test get_count_order/long in test

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Date:   Thu, 4 Jun 2020 14:51:40 +0200
From:   Geert Uytterhoeven <geert@...ux-m68k.org>
To:     Wei Yang <richard.weiyang@...il.com>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Christian Brauner <christian.brauner@...ntu.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [Patch v2] lib: test get_count_order/long in test_bitops.c

Hi Wei,

On Thu, Jun 4, 2020 at 2:28 PM Wei Yang <richard.weiyang@...il.com> wrote:
> On Thu, Jun 04, 2020 at 01:50:13PM +0200, Geert Uytterhoeven wrote:
> >On Wed, Jun 3, 2020 at 1:11 AM Wei Yang <richard.weiyang@...il.com> wrote:
> >> Add some test for get_count_order/long in test_bitops.c.
> >>
> >> Signed-off-by: Wei Yang <richard.weiyang@...il.com>
> >
> >Thanks for your patch, which is now commit 7851d6639caeea40 ("lib:
> >test get_count_order/long in test_bitops.c") in linux-next.
> >
> >> --- a/lib/test_bitops.c
> >> +++ b/lib/test_bitops.c
> >
> >> @@ -24,6 +28,26 @@ enum bitops_fun {
> >>
> >>  static DECLARE_BITMAP(g_bitmap, BITOPS_LENGTH);
> >>
> >> +unsigned int order_comb[][2] = {
> >> +       {0x00000003,  2},
> >> +       {0x00000004,  2},
> >> +       {0x00001fff, 13},
> >> +       {0x00002000, 13},
> >> +       {0x50000000, 31},
> >> +       {0x80000000, 31},
> >> +       {0x80003000, 32},
> >> +};
> >> +
> >> +unsigned long order_comb_long[][2] = {
> >> +       {0x0000000300000000, 34},
> >> +       {0x0000000400000000, 34},
> >> +       {0x00001fff00000000, 45},
> >> +       {0x0000200000000000, 45},
> >> +       {0x5000000000000000, 63},
> >> +       {0x8000000000000000, 63},
> >> +       {0x8000300000000000, 64},
> >> +};
> >
> >noreply@...erman.id.au reported for m68k-allmodconfig:
> >
> >lib/test_bitops.c:42:3: error: unsigned conversion from 'long long
> >int' to 'long unsigned int' changes value from '12884901888' to '0'
> >[-Werror=overflow]
> >lib/test_bitops.c:43:3: error: unsigned conversion from 'long long
> >int' to 'long unsigned int' changes value from '17179869184' to '0'
> >[-Werror=overflow]
> >lib/test_bitops.c:44:3: error: unsigned conversion from 'long long
> >int' to 'long unsigned int' changes value from '35180077121536' to '0'
> >[-Werror=overflow]
> >lib/test_bitops.c:45:3: error: unsigned conversion from 'long long
> >int' to 'long unsigned int' changes value from '35184372088832' to '0'
> >[-Werror=overflow]
> >lib/test_bitops.c:46:3: error: unsigned conversion from 'long long
> >int' to 'long unsigned int' changes value from '5764607523034234880'
> >to '0' [-Werror=overflow]
> >lib/test_bitops.c:47:3: error: conversion from 'long long unsigned
> >int' to 'long unsigned int' changes value from '9223372036854775808'
> >to '0' [-Werror=overflow]
> >lib/test_bitops.c:48:3: error: conversion from 'long long unsigned
> >int' to 'long unsigned int' changes value from '9223424813412909056'
> >to '0' [-Werror=overflow]
> >
> >Indeed, on 32-bit, none of these values fit in unsigned long.
> >
>
> Hmm... I didn't test on 32bit platform. Sorry for that.
>
> >>  static int __init test_bitops_startup(void)
> >>  {
> >>         pr_warn("Loaded test module\n");
> >> @@ -32,6 +56,18 @@ static int __init test_bitops_startup(void)
> >>         set_bit(BITOPS_11, g_bitmap);
> >>         set_bit(BITOPS_31, g_bitmap);
> >>         set_bit(BITOPS_88, g_bitmap);
> >> +
> >> +       for (i = 0; i < ARRAY_SIZE(order_comb); i++) {
> >> +               if (order_comb[i][1] != get_count_order(order_comb[i][0]))
> >> +                       pr_warn("get_count_order wrong for %x\n",
> >> +                                      order_comb[i][0]); }
> >> +
> >> +       for (i = 0; i < ARRAY_SIZE(order_comb_long); i++) {
> >> +               if (order_comb_long[i][1] !=
> >> +                              get_count_order_long(order_comb_long[i][0]))
> >> +                       pr_warn("get_count_order_long wrong for %lx\n",
> >> +                                      order_comb_long[i][0]); }
> >> +
> >>         return 0;
> >
> >BTW, shouldn't get_count_order_long() be tested with the values in
> >order_comb[], too?
> >
>
> You mean
>
>        {0x0000000000000003,  2},
>        {0x0000000000000004,  2},
>        {0x0000000000001fff, 13},
>        {0x0000000000002000, 13},
>        {0x0000000050000000, 31},
>        {0x0000000080000000, 31},
>        {0x0000000080003000, 32},

Yes, those values.  And those should work with get_count_order_long()
on both 32-bit and 64-bit.

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds