Re: [PATCH V2 3/3] SH: cpuinfo: Fix a warning for CONFIG_CPUMASK_OFFSTACK

[Huacai Chen]

Hi, SuperH maintainers,

On Wed, Feb 8, 2023 at 8:59 PM John Paul Adrian Glaubitz
<glaubitz@xxxxxxxxxxxxxxxxxxx> wrote:
>
> On Thu, 2022-07-14 at 16:41 +0800, Huacai Chen wrote:
> > When CONFIG_CPUMASK_OFFSTACK and CONFIG_DEBUG_PER_CPU_MAPS is selected,
> > cpu_max_bits_warn() generates a runtime warning similar as below while
> > we show /proc/cpuinfo. Fix this by using nr_cpu_ids (the runtime limit)
> > instead of NR_CPUS to iterate CPUs.
> >
> > [    3.052463] ------------[ cut here ]------------
> > [    3.059679] WARNING: CPU: 3 PID: 1 at include/linux/cpumask.h:108 show_cpuinfo+0x5e8/0x5f0
> > [    3.070072] Modules linked in: efivarfs autofs4
> > [    3.076257] CPU: 0 PID: 1 Comm: systemd Not tainted 5.19-rc5+ #1052
> > [    3.099465] Stack : 9000000100157b08 9000000000f18530 9000000000cf846c 9000000100154000
> > [    3.109127]         9000000100157a50 0000000000000000 9000000100157a58 9000000000ef7430
> > [    3.118774]         90000001001578e8 0000000000000040 0000000000000020 ffffffffffffffff
> > [    3.128412]         0000000000aaaaaa 1ab25f00eec96a37 900000010021de80 900000000101c890
> > [    3.138056]         0000000000000000 0000000000000000 0000000000000000 0000000000aaaaaa
> > [    3.147711]         ffff8000339dc220 0000000000000001 0000000006ab4000 0000000000000000
> > [    3.157364]         900000000101c998 0000000000000004 9000000000ef7430 0000000000000000
> > [    3.167012]         0000000000000009 000000000000006c 0000000000000000 0000000000000000
> > [    3.176641]         9000000000d3de08 9000000001639390 90000000002086d8 00007ffff0080286
> > [    3.186260]         00000000000000b0 0000000000000004 0000000000000000 0000000000071c1c
> > [    3.195868]         ...
> > [    3.199917] Call Trace:
> > [    3.203941] [<90000000002086d8>] show_stack+0x38/0x14c
> > [    3.210666] [<9000000000cf846c>] dump_stack_lvl+0x60/0x88
> > [    3.217625] [<900000000023d268>] __warn+0xd0/0x100
> > [    3.223958] [<9000000000cf3c90>] warn_slowpath_fmt+0x7c/0xcc
> > [    3.231150] [<9000000000210220>] show_cpuinfo+0x5e8/0x5f0
> > [    3.238080] [<90000000004f578c>] seq_read_iter+0x354/0x4b4
> > [    3.245098] [<90000000004c2e90>] new_sync_read+0x17c/0x1c4
> > [    3.252114] [<90000000004c5174>] vfs_read+0x138/0x1d0
> > [    3.258694] [<90000000004c55f8>] ksys_read+0x70/0x100
> > [    3.265265] [<9000000000cfde9c>] do_syscall+0x7c/0x94
> > [    3.271820] [<9000000000202fe4>] handle_syscall+0xc4/0x160
> > [    3.281824] ---[ end trace 8b484262b4b8c24c ]---
> >
> > Cc: stable@xxxxxxxxxxxxxxx
> > Signed-off-by: Huacai Chen <chenhuacai@xxxxxxxxxxx>
> > ---
> >  arch/sh/kernel/cpu/proc.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/arch/sh/kernel/cpu/proc.c b/arch/sh/kernel/cpu/proc.c
> > index a306bcd6b341..5f6d0e827bae 100644
> > --- a/arch/sh/kernel/cpu/proc.c
> > +++ b/arch/sh/kernel/cpu/proc.c
> > @@ -132,7 +132,7 @@ static int show_cpuinfo(struct seq_file *m, void *v)
> >
> >  static void *c_start(struct seq_file *m, loff_t *pos)
> >  {
> > -     return *pos < NR_CPUS ? cpu_data + *pos : NULL;
> > +     return *pos < nr_cpu_ids ? cpu_data + *pos : NULL;
> >  }
> >  static void *c_next(struct seq_file *m, void *v, loff_t *pos)
> >  {
>
> I build-tested the patch and also booted the patched kernel successfully
> on my SH-7785LCR board.
>
> Showing the contents of /proc/cpuinfo works fine, too:
>
> root@tirpitz:~> cat /proc/cpuinfo
> machine         : SH7785LCR
> processor       : 0
> cpu family      : sh4a
> cpu type        : SH7785
> cut             : 7.x
> cpu flags       : fpu perfctr llsc
> cache type      : split (harvard)
> icache size     : 32KiB (4-way)
> dcache size     : 32KiB (4-way)
> address sizes   : 32 bits physical
> bogomips        : 599.99
> root@tirpitz:~>
>
> Tested-by: John Paul Adrian Glaubitz <glaubitz@xxxxxxxxxxxxxxxxxxx>
>
> I am not sure yet whether the change is also correct as I don't know whether
> it's possible to change the number of CPUs at runtime on SuperH.
Can this patch be merged? This is the only one still unmerged in the
whole series.

Huacai

>
> Adrian
>
> --
>  .''`.  John Paul Adrian Glaubitz
> : :' :  Debian Developer
> `. `'   Physicist
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