[PATCH] asm-generic/mmiowb: Get cpu in mmiowb_set_pending

[Guo Ren]

Hi Emil,

On Sun, Jul 5, 2020 at 10:27 PM Emil Renner Berthing <kernel at esmil.dk> wrote:
>
> Without this enabling CONFIG_PREEMPT and CONFIG_DEBUG_PREEMPT
> results in many errors like this on the HiFive Unleashed
> RISC-V board:
>
> BUG: using smp_processor_id() in preemptible [00000000] code: swapper/0/1
> caller is regmap_mmio_write32le+0x1c/0x46
> CPU: 3 PID: 1 Comm: swapper/0 Not tainted 5.8.0-rc3-hfu+ #1
> Call Trace:
> [<ffffffe000201f6e>] walk_stackframe+0x0/0x7a
> [<ffffffe0005b290e>] dump_stack+0x6e/0x88
> [<ffffffe00047365e>] regmap_mmio_write32le+0x18/0x46
> [<ffffffe0005c4c26>] check_preemption_disabled+0xa4/0xaa
> [<ffffffe00047365e>] regmap_mmio_write32le+0x18/0x46
> [<ffffffe0004737c8>] regmap_mmio_write+0x26/0x44
> [<ffffffe0004715c4>] regmap_write+0x28/0x48
> [<ffffffe00043dccc>] sifive_gpio_probe+0xc0/0x1da
> [<ffffffe00000113e>] rdinit_setup+0x22/0x26
> [<ffffffe000469054>] platform_drv_probe+0x24/0x52
> [<ffffffe000467e16>] really_probe+0x92/0x21a
> [<ffffffe0004683a8>] device_driver_attach+0x42/0x4a
> [<ffffffe0004683ac>] device_driver_attach+0x46/0x4a
> [<ffffffe0004683f0>] __driver_attach+0x40/0xac
> [<ffffffe0004683ac>] device_driver_attach+0x46/0x4a
> [<ffffffe000466a3e>] bus_for_each_dev+0x3c/0x64
> [<ffffffe000467118>] bus_add_driver+0x11e/0x184
> [<ffffffe00046889a>] driver_register+0x32/0xc6
> [<ffffffe00000e5ac>] gpiolib_sysfs_init+0xaa/0xae
> [<ffffffe0000019ec>] do_one_initcall+0x50/0xfc
> [<ffffffe00000113e>] rdinit_setup+0x22/0x26
> [<ffffffe000001bea>] kernel_init_freeable+0x152/0x1da
> [<ffffffe0005c4d28>] rest_init+0xde/0xe2
> [<ffffffe0005c4d36>] kernel_init+0xa/0x11a
> [<ffffffe0005c4d28>] rest_init+0xde/0xe2
> [<ffffffe000200ff6>] ret_from_syscall_rejected+0x8/0xc
>
> Signed-off-by: Emil Renner Berthing <kernel at esmil.dk>
> ---
> This patch fixes it, but my guess is that it's not the right
> fix. Do anyone have a better idea?
>
>  include/asm-generic/mmiowb.h | 6 +++++-
>  1 file changed, 5 insertions(+), 1 deletion(-)
>
> diff --git a/include/asm-generic/mmiowb.h b/include/asm-generic/mmiowb.h
> index 9439ff037b2d..31a21cdfbbcf 100644
> --- a/include/asm-generic/mmiowb.h
> +++ b/include/asm-generic/mmiowb.h
> @@ -34,8 +34,12 @@ DECLARE_PER_CPU(struct mmiowb_state, __mmiowb_state);
>
>  static inline void mmiowb_set_pending(void)
>  {
> -       struct mmiowb_state *ms = __mmiowb_state();
> +       struct mmiowb_state *ms;
> +
> +       get_cpu();
> +       ms = __mmiowb_state();
>         ms->mmiowb_pending = ms->nesting_count;
> +       put_cpu();
>  }

#define __mmiowb_state()        this_cpu_ptr(&__mmiowb_state)

The ptr is a fixed address, so don't worry about the change, and just
use an atomic_read is enough.
static inline void mmiowb_set_pending(void)
{
        struct mmiowb_state *ms = __mmiowb_state();
-       ms->mmiowb_pending = ms->nesting_count;
+      ms->mmiowb_pending = atomic_read(ms->nesting_count);
}


-- 
Best Regards
 Guo Ren

ML: https://lore.kernel.org/linux-csky/