linux-kernel - Re: [PATCH v2] ACPI: CPPC: Make rmw_lock a raw_spin

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Message-ID: <CAJZ5v0jzDxAe6FmVOigd-EnAOkgOhbtdPp-ZrVGQqjpxAnabRQ@mail.gmail.com>
Date: Tue, 29 Oct 2024 13:03:30 +0100
From: "Rafael J. Wysocki" <rafael@...nel.org>
To: Pierre Gondois <pierre.gondois@....com>
Cc: linux-kernel@...r.kernel.org, "Rafael J. Wysocki" <rafael@...nel.org>, 
	Len Brown <lenb@...nel.org>, Robert Moore <robert.moore@...el.com>, 
	Clément Léger <cleger@...osinc.com>, 
	linux-acpi@...r.kernel.org, acpica-devel@...ts.linux.dev
Subject: Re: [PATCH v2] ACPI: CPPC: Make rmw_lock a raw_spin_lock

On Mon, Oct 28, 2024 at 1:57 PM Pierre Gondois <pierre.gondois@....com> wrote:
>
> The following BUG was triggered. sugov_update_shared() locks a
> raw_spinlock while cpc_write() locks a spinlock. To have a correct
> wait-type order, update rmw_lock to a raw_spinlock.
>
> Also save irq state.
>
> =============================
> [ BUG: Invalid wait context ]
> 6.12.0-rc2-XXX #406 Not tainted
> -----------------------------
> kworker/1:1/62 is trying to lock:
> ffffff8801593030 (&cpc_ptr->rmw_lock){+.+.}-{3:3}, at: cpc_write+0xcc/0x370
> other info that might help us debug this:
> context-{5:5}
> 2 locks held by kworker/1:1/62:
>   #0: ffffff897ef5ec98 (&rq->__lock){-.-.}-{2:2}, at: raw_spin_rq_lock_nested+0x2c/0x50
>   #1: ffffff880154e238 (&sg_policy->update_lock){....}-{2:2}, at: sugov_update_shared+0x3c/0x280
> stack backtrace:
> CPU: 1 UID: 0 PID: 62 Comm: kworker/1:1 Not tainted 6.12.0-rc2-g9654bd3e8806 #406
> Workqueue:  0x0 (events)
> Call trace:
>   dump_backtrace+0xa4/0x130
>   show_stack+0x20/0x38
>   dump_stack_lvl+0x90/0xd0
>   dump_stack+0x18/0x28
>   __lock_acquire+0x480/0x1ad8
>   lock_acquire+0x114/0x310
>   _raw_spin_lock+0x50/0x70
>   cpc_write+0xcc/0x370
>   cppc_set_perf+0xa0/0x3a8
>   cppc_cpufreq_fast_switch+0x40/0xc0
>   cpufreq_driver_fast_switch+0x4c/0x218
>   sugov_update_shared+0x234/0x280
>   update_load_avg+0x6ec/0x7b8
>   dequeue_entities+0x108/0x830
>   dequeue_task_fair+0x58/0x408
>   __schedule+0x4f0/0x1070
>   schedule+0x54/0x130
>   worker_thread+0xc0/0x2e8
>   kthread+0x130/0x148
>   ret_from_fork+0x10/0x20
>
> Fixes: 60949b7b8054 ("ACPI: CPPC: Fix MASK_VAL() usage")
> Signed-off-by: Pierre Gondois <pierre.gondois@....com>
> ---
>
> Notes:
>     v2:
>     - Do the actual changes.
>
>  drivers/acpi/cppc_acpi.c | 9 +++++----
>  include/acpi/cppc_acpi.h | 2 +-
>  2 files changed, 6 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/acpi/cppc_acpi.c b/drivers/acpi/cppc_acpi.c
> index c3fc2c05d868..1a40f0514eaa 100644
> --- a/drivers/acpi/cppc_acpi.c
> +++ b/drivers/acpi/cppc_acpi.c
> @@ -867,7 +867,7 @@ int acpi_cppc_processor_probe(struct acpi_processor *pr)
>
>         /* Store CPU Logical ID */
>         cpc_ptr->cpu_id = pr->id;
> -       spin_lock_init(&cpc_ptr->rmw_lock);
> +       raw_spin_lock_init(&cpc_ptr->rmw_lock);
>
>         /* Parse PSD data for this CPU */
>         ret = acpi_get_psd(cpc_ptr, handle);
> @@ -1087,6 +1087,7 @@ static int cpc_write(int cpu, struct cpc_register_resource *reg_res, u64 val)
>         int pcc_ss_id = per_cpu(cpu_pcc_subspace_idx, cpu);
>         struct cpc_reg *reg = &reg_res->cpc_entry.reg;
>         struct cpc_desc *cpc_desc;
> +       unsigned long flags;
>
>         size = GET_BIT_WIDTH(reg);
>
> @@ -1126,7 +1127,7 @@ static int cpc_write(int cpu, struct cpc_register_resource *reg_res, u64 val)
>                         return -ENODEV;
>                 }
>
> -               spin_lock(&cpc_desc->rmw_lock);
> +               raw_spin_lock_irqsave(&cpc_desc->rmw_lock, flags);
>                 switch (size) {
>                 case 8:
>                         prev_val = readb_relaxed(vaddr);
> @@ -1141,7 +1142,7 @@ static int cpc_write(int cpu, struct cpc_register_resource *reg_res, u64 val)
>                         prev_val = readq_relaxed(vaddr);
>                         break;
>                 default:
> -                       spin_unlock(&cpc_desc->rmw_lock);
> +                       raw_spin_unlock_irqrestore(&cpc_desc->rmw_lock, flags);
>                         return -EFAULT;
>                 }
>                 val = MASK_VAL_WRITE(reg, prev_val, val);
> @@ -1174,7 +1175,7 @@ static int cpc_write(int cpu, struct cpc_register_resource *reg_res, u64 val)
>         }
>
>         if (reg->space_id == ACPI_ADR_SPACE_SYSTEM_MEMORY)
> -               spin_unlock(&cpc_desc->rmw_lock);
> +               raw_spin_unlock_irqrestore(&cpc_desc->rmw_lock, flags);
>
>         return ret_val;
>  }
> diff --git a/include/acpi/cppc_acpi.h b/include/acpi/cppc_acpi.h
> index 76e44e102780..62d368bcd9ec 100644
> --- a/include/acpi/cppc_acpi.h
> +++ b/include/acpi/cppc_acpi.h
> @@ -65,7 +65,7 @@ struct cpc_desc {
>         int write_cmd_status;
>         int write_cmd_id;
>         /* Lock used for RMW operations in cpc_write() */
> -       spinlock_t rmw_lock;
> +       raw_spinlock_t rmw_lock;
>         struct cpc_register_resource cpc_regs[MAX_CPC_REG_ENT];
>         struct acpi_psd_package domain_info;
>         struct kobject kobj;
> --

Applied (with edited changelog) as 6.12-rc material, thanks!