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

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Message-Id: <20241028125657.1271512-1-pierre.gondois@arm.com>
Date: Mon, 28 Oct 2024 13:56:56 +0100
From: Pierre Gondois <pierre.gondois@....com>
To: linux-kernel@...r.kernel.org
Cc: Pierre Gondois <pierre.gondois@....com>,
	"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: [PATCH v2] ACPI: CPPC: Make rmw_lock a raw_spin_lock

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;
-- 
2.25.1