[PATCH v1 0/3] ACPI: OSL/EC: Use spin locks without disabling interrupts

[PATCH v1 0/3] ACPI: OSL/EC: Use spin locks without disabling interrupts

[Rafael J. Wysocki]

Hi Everyone,

After

https://patchwork.kernel.org/project/linux-acpi/patch/5745568.DvuYhMxLoT@kreacher/

the SCI interrupt handler is threaded, so ACPICA spin locks can be used without
disabling interrupts, because they cannot be acquired from a hardirq handler
running on the same CPU as any code already holding the spin lock.  This patch
[1/3] removes disabling interrupts from acpi_os_acquire_lock() and updates
acpi_os_release_lock() accordingly.

Patch [2/2] uses the observation that if acpi_handle_interrupt() can run
in a threaded interrupt handler in the GPE case, it can also run in a threaded
interrupt handler in the dedicated IRQ case, so it makes the EC driver use a
threaded handler for the dedicated EC interrupt.

Patch [3/3], in analogy with patch [1/3], uses the observation that after patch
[2/2] all of the EC code runs in thread context, so it need not disable
interrupts on the local CPU before acquiring a spin lock, so the EC driver is
updated to operate its spin lock without disabling interrupts.

Thanks!

[PATCH v1 1/3] ACPI: OSL: Use spin locks without disabling interrupts

[Rafael J. Wysocki]

From: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

After commit 7a36b901a6eb ("ACPI: OSL: Use a threaded interrupt handler
for SCI") any ACPICA code never runs in a hardirq handler, so it need
not dissable interrupts on the local CPU when acquiring a spin lock.

Make it use spin locks without disabling interrupts.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
---
 drivers/acpi/osl.c |   10 ++++------
 1 file changed, 4 insertions(+), 6 deletions(-)

Index: linux-pm/drivers/acpi/osl.c
===================================================================
--- linux-pm.orig/drivers/acpi/osl.c
+++ linux-pm/drivers/acpi/osl.c
@@ -1515,20 +1515,18 @@ void acpi_os_delete_lock(acpi_spinlock h
 acpi_cpu_flags acpi_os_acquire_lock(acpi_spinlock lockp)
 	__acquires(lockp)
 {
-	acpi_cpu_flags flags;
-
-	spin_lock_irqsave(lockp, flags);
-	return flags;
+	spin_lock(lockp);
+	return 0;
 }
 
 /*
  * Release a spinlock. See above.
  */
 
-void acpi_os_release_lock(acpi_spinlock lockp, acpi_cpu_flags flags)
+void acpi_os_release_lock(acpi_spinlock lockp, acpi_cpu_flags not_used)
 	__releases(lockp)
 {
-	spin_unlock_irqrestore(lockp, flags);
+	spin_unlock(lockp);
 }
 
 #ifndef ACPI_USE_LOCAL_CACHE

[PATCH v1 2/3] ACPI: EC: Use a threaded handler for dedicated IRQ

[Rafael J. Wysocki]

From: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

After commit 7a36b901a6eb ("ACPI: OSL: Use a threaded interrupt handler
for SCI") all of the EC code runs in thread context on all systems where
EC events are signaled through a GPE.

It may as well run in thread context on systems using a dedicated IRQ
for EC events signaling, so make it use a threaded handler for that IRQ.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
---
 drivers/acpi/ec.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

Index: linux-pm/drivers/acpi/ec.c
===================================================================
--- linux-pm.orig/drivers/acpi/ec.c
+++ linux-pm/drivers/acpi/ec.c
@@ -1458,8 +1458,8 @@ static bool install_gpe_event_handler(st
 
 static bool install_gpio_irq_event_handler(struct acpi_ec *ec)
 {
-	return request_irq(ec->irq, acpi_ec_irq_handler, IRQF_SHARED,
-			   "ACPI EC", ec) >= 0;
+	return request_threaded_irq(ec->irq, NULL, acpi_ec_irq_handler,
+				    IRQF_SHARED | IRQF_ONESHOT, "ACPI EC", ec) >= 0;
 }
 
 /**

[PATCH v1 3/3] ACPI: EC: Use a spin lock without disabing interrupts

[Rafael J. Wysocki]

From: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

Since all of the ACPI EC driver code runs in thread context after recent
changes, it does not need to disable interrupts on the local CPU when
acquiring a spin lock.

Make it use the spin lock without disabling interrupts.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
---
 drivers/acpi/ec.c |  112 ++++++++++++++++++++++--------------------------------
 1 file changed, 46 insertions(+), 66 deletions(-)

Index: linux-pm/drivers/acpi/ec.c
===================================================================
--- linux-pm.orig/drivers/acpi/ec.c
+++ linux-pm/drivers/acpi/ec.c
@@ -525,12 +525,10 @@ static void acpi_ec_clear(struct acpi_ec
 
 static void acpi_ec_enable_event(struct acpi_ec *ec)
 {
-	unsigned long flags;
-
-	spin_lock_irqsave(&ec->lock, flags);
+	spin_lock(&ec->lock);
 	if (acpi_ec_started(ec))
 		__acpi_ec_enable_event(ec);
-	spin_unlock_irqrestore(&ec->lock, flags);
+	spin_unlock(&ec->lock);
 
 	/* Drain additional events if hardware requires that */
 	if (EC_FLAGS_CLEAR_ON_RESUME)
@@ -546,11 +544,9 @@ static void __acpi_ec_flush_work(void)
 
 static void acpi_ec_disable_event(struct acpi_ec *ec)
 {
-	unsigned long flags;
-
-	spin_lock_irqsave(&ec->lock, flags);
+	spin_lock(&ec->lock);
 	__acpi_ec_disable_event(ec);
-	spin_unlock_irqrestore(&ec->lock, flags);
+	spin_unlock(&ec->lock);
 
 	/*
 	 * When ec_freeze_events is true, we need to flush events in
@@ -571,10 +567,9 @@ void acpi_ec_flush_work(void)
 
 static bool acpi_ec_guard_event(struct acpi_ec *ec)
 {
-	unsigned long flags;
 	bool guarded;
 
-	spin_lock_irqsave(&ec->lock, flags);
+	spin_lock(&ec->lock);
 	/*
 	 * If firmware SCI_EVT clearing timing is "event", we actually
 	 * don't know when the SCI_EVT will be cleared by firmware after
@@ -590,31 +585,29 @@ static bool acpi_ec_guard_event(struct a
 	guarded = ec_event_clearing == ACPI_EC_EVT_TIMING_EVENT &&
 		ec->event_state != EC_EVENT_READY &&
 		(!ec->curr || ec->curr->command != ACPI_EC_COMMAND_QUERY);
-	spin_unlock_irqrestore(&ec->lock, flags);
+	spin_unlock(&ec->lock);
 	return guarded;
 }
 
 static int ec_transaction_polled(struct acpi_ec *ec)
 {
-	unsigned long flags;
 	int ret = 0;
 
-	spin_lock_irqsave(&ec->lock, flags);
+	spin_lock(&ec->lock);
 	if (ec->curr && (ec->curr->flags & ACPI_EC_COMMAND_POLL))
 		ret = 1;
-	spin_unlock_irqrestore(&ec->lock, flags);
+	spin_unlock(&ec->lock);
 	return ret;
 }
 
 static int ec_transaction_completed(struct acpi_ec *ec)
 {
-	unsigned long flags;
 	int ret = 0;
 
-	spin_lock_irqsave(&ec->lock, flags);
+	spin_lock(&ec->lock);
 	if (ec->curr && (ec->curr->flags & ACPI_EC_COMMAND_COMPLETE))
 		ret = 1;
-	spin_unlock_irqrestore(&ec->lock, flags);
+	spin_unlock(&ec->lock);
 	return ret;
 }
 
@@ -756,7 +749,6 @@ static int ec_guard(struct acpi_ec *ec)
 
 static int ec_poll(struct acpi_ec *ec)
 {
-	unsigned long flags;
 	int repeat = 5; /* number of command restarts */
 
 	while (repeat--) {
@@ -765,14 +757,14 @@ static int ec_poll(struct acpi_ec *ec)
 		do {
 			if (!ec_guard(ec))
 				return 0;
-			spin_lock_irqsave(&ec->lock, flags);
+			spin_lock(&ec->lock);
 			advance_transaction(ec, false);
-			spin_unlock_irqrestore(&ec->lock, flags);
+			spin_unlock(&ec->lock);
 		} while (time_before(jiffies, delay));
 		pr_debug("controller reset, restart transaction\n");
-		spin_lock_irqsave(&ec->lock, flags);
+		spin_lock(&ec->lock);
 		start_transaction(ec);
-		spin_unlock_irqrestore(&ec->lock, flags);
+		spin_unlock(&ec->lock);
 	}
 	return -ETIME;
 }
@@ -780,11 +772,10 @@ static int ec_poll(struct acpi_ec *ec)
 static int acpi_ec_transaction_unlocked(struct acpi_ec *ec,
 					struct transaction *t)
 {
-	unsigned long tmp;
 	int ret = 0;
 
 	/* start transaction */
-	spin_lock_irqsave(&ec->lock, tmp);
+	spin_lock(&ec->lock);
 	/* Enable GPE for command processing (IBF=0/OBF=1) */
 	if (!acpi_ec_submit_flushable_request(ec)) {
 		ret = -EINVAL;
@@ -795,11 +786,11 @@ static int acpi_ec_transaction_unlocked(
 	ec->curr = t;
 	ec_dbg_req("Command(%s) started", acpi_ec_cmd_string(t->command));
 	start_transaction(ec);
-	spin_unlock_irqrestore(&ec->lock, tmp);
+	spin_unlock(&ec->lock);
 
 	ret = ec_poll(ec);
 
-	spin_lock_irqsave(&ec->lock, tmp);
+	spin_lock(&ec->lock);
 	if (t->irq_count == ec_storm_threshold)
 		acpi_ec_unmask_events(ec);
 	ec_dbg_req("Command(%s) stopped", acpi_ec_cmd_string(t->command));
@@ -808,7 +799,7 @@ static int acpi_ec_transaction_unlocked(
 	acpi_ec_complete_request(ec);
 	ec_dbg_ref(ec, "Decrease command");
 unlock:
-	spin_unlock_irqrestore(&ec->lock, tmp);
+	spin_unlock(&ec->lock);
 	return ret;
 }
 
@@ -936,9 +927,7 @@ EXPORT_SYMBOL(ec_get_handle);
 
 static void acpi_ec_start(struct acpi_ec *ec, bool resuming)
 {
-	unsigned long flags;
-
-	spin_lock_irqsave(&ec->lock, flags);
+	spin_lock(&ec->lock);
 	if (!test_and_set_bit(EC_FLAGS_STARTED, &ec->flags)) {
 		ec_dbg_drv("Starting EC");
 		/* Enable GPE for event processing (SCI_EVT=1) */
@@ -948,31 +937,28 @@ static void acpi_ec_start(struct acpi_ec
 		}
 		ec_log_drv("EC started");
 	}
-	spin_unlock_irqrestore(&ec->lock, flags);
+	spin_unlock(&ec->lock);
 }
 
 static bool acpi_ec_stopped(struct acpi_ec *ec)
 {
-	unsigned long flags;
 	bool flushed;
 
-	spin_lock_irqsave(&ec->lock, flags);
+	spin_lock(&ec->lock);
 	flushed = acpi_ec_flushed(ec);
-	spin_unlock_irqrestore(&ec->lock, flags);
+	spin_unlock(&ec->lock);
 	return flushed;
 }
 
 static void acpi_ec_stop(struct acpi_ec *ec, bool suspending)
 {
-	unsigned long flags;
-
-	spin_lock_irqsave(&ec->lock, flags);
+	spin_lock(&ec->lock);
 	if (acpi_ec_started(ec)) {
 		ec_dbg_drv("Stopping EC");
 		set_bit(EC_FLAGS_STOPPED, &ec->flags);
-		spin_unlock_irqrestore(&ec->lock, flags);
+		spin_unlock(&ec->lock);
 		wait_event(ec->wait, acpi_ec_stopped(ec));
-		spin_lock_irqsave(&ec->lock, flags);
+		spin_lock(&ec->lock);
 		/* Disable GPE for event processing (SCI_EVT=1) */
 		if (!suspending) {
 			acpi_ec_complete_request(ec);
@@ -983,29 +969,25 @@ static void acpi_ec_stop(struct acpi_ec
 		clear_bit(EC_FLAGS_STOPPED, &ec->flags);
 		ec_log_drv("EC stopped");
 	}
-	spin_unlock_irqrestore(&ec->lock, flags);
+	spin_unlock(&ec->lock);
 }
 
 static void acpi_ec_enter_noirq(struct acpi_ec *ec)
 {
-	unsigned long flags;
-
-	spin_lock_irqsave(&ec->lock, flags);
+	spin_lock(&ec->lock);
 	ec->busy_polling = true;
 	ec->polling_guard = 0;
 	ec_log_drv("interrupt blocked");
-	spin_unlock_irqrestore(&ec->lock, flags);
+	spin_unlock(&ec->lock);
 }
 
 static void acpi_ec_leave_noirq(struct acpi_ec *ec)
 {
-	unsigned long flags;
-
-	spin_lock_irqsave(&ec->lock, flags);
+	spin_lock(&ec->lock);
 	ec->busy_polling = ec_busy_polling;
 	ec->polling_guard = ec_polling_guard;
 	ec_log_drv("interrupt unblocked");
-	spin_unlock_irqrestore(&ec->lock, flags);
+	spin_unlock(&ec->lock);
 }
 
 void acpi_ec_block_transactions(void)
@@ -1137,9 +1119,9 @@ static void acpi_ec_event_processor(stru
 
 	ec_dbg_evt("Query(0x%02x) stopped", handler->query_bit);
 
-	spin_lock_irq(&ec->lock);
+	spin_lock(&ec->lock);
 	ec->queries_in_progress--;
-	spin_unlock_irq(&ec->lock);
+	spin_unlock(&ec->lock);
 
 	acpi_ec_put_query_handler(handler);
 	kfree(q);
@@ -1202,12 +1184,12 @@ static int acpi_ec_submit_query(struct a
 	 */
 	ec_dbg_evt("Query(0x%02x) scheduled", value);
 
-	spin_lock_irq(&ec->lock);
+	spin_lock(&ec->lock);
 
 	ec->queries_in_progress++;
 	queue_work(ec_query_wq, &q->work);
 
-	spin_unlock_irq(&ec->lock);
+	spin_unlock(&ec->lock);
 
 	return 0;
 
@@ -1223,14 +1205,14 @@ static void acpi_ec_event_handler(struct
 
 	ec_dbg_evt("Event started");
 
-	spin_lock_irq(&ec->lock);
+	spin_lock(&ec->lock);
 
 	while (ec->events_to_process) {
-		spin_unlock_irq(&ec->lock);
+		spin_unlock(&ec->lock);
 
 		acpi_ec_submit_query(ec);
 
-		spin_lock_irq(&ec->lock);
+		spin_lock(&ec->lock);
 
 		ec->events_to_process--;
 	}
@@ -1247,11 +1229,11 @@ static void acpi_ec_event_handler(struct
 
 		ec_dbg_evt("Event stopped");
 
-		spin_unlock_irq(&ec->lock);
+		spin_unlock(&ec->lock);
 
 		guard_timeout = !!ec_guard(ec);
 
-		spin_lock_irq(&ec->lock);
+		spin_lock(&ec->lock);
 
 		/* Take care of SCI_EVT unless someone else is doing that. */
 		if (guard_timeout && !ec->curr)
@@ -1264,7 +1246,7 @@ static void acpi_ec_event_handler(struct
 
 	ec->events_in_progress--;
 
-	spin_unlock_irq(&ec->lock);
+	spin_unlock(&ec->lock);
 }
 
 static void clear_gpe_and_advance_transaction(struct acpi_ec *ec, bool interrupt)
@@ -1289,13 +1271,11 @@ static void clear_gpe_and_advance_transa
 
 static void acpi_ec_handle_interrupt(struct acpi_ec *ec)
 {
-	unsigned long flags;
-
-	spin_lock_irqsave(&ec->lock, flags);
+	spin_lock(&ec->lock);
 
 	clear_gpe_and_advance_transaction(ec, true);
 
-	spin_unlock_irqrestore(&ec->lock, flags);
+	spin_unlock(&ec->lock);
 }
 
 static u32 acpi_ec_gpe_handler(acpi_handle gpe_device,
@@ -2105,7 +2085,7 @@ bool acpi_ec_dispatch_gpe(void)
 	 * Dispatch the EC GPE in-band, but do not report wakeup in any case
 	 * to allow the caller to process events properly after that.
 	 */
-	spin_lock_irq(&first_ec->lock);
+	spin_lock(&first_ec->lock);
 
 	if (acpi_ec_gpe_status_set(first_ec)) {
 		pm_pr_dbg("ACPI EC GPE status set\n");
@@ -2114,7 +2094,7 @@ bool acpi_ec_dispatch_gpe(void)
 		work_in_progress = acpi_ec_work_in_progress(first_ec);
 	}
 
-	spin_unlock_irq(&first_ec->lock);
+	spin_unlock(&first_ec->lock);
 
 	if (!work_in_progress)
 		return false;
@@ -2127,11 +2107,11 @@ bool acpi_ec_dispatch_gpe(void)
 
 		pm_pr_dbg("ACPI EC work flushed\n");
 
-		spin_lock_irq(&first_ec->lock);
+		spin_lock(&first_ec->lock);
 
 		work_in_progress = acpi_ec_work_in_progress(first_ec);
 
-		spin_unlock_irq(&first_ec->lock);
+		spin_unlock(&first_ec->lock);
 	} while (work_in_progress && !pm_wakeup_pending());
 
 	return false;

Re: [PATCH v1 0/3] ACPI: OSL/EC: Use spin locks without disabling interrupts

[Rafael J. Wysocki]

On Fri, Dec 15, 2023 at 12:34 PM Rafael J. Wysocki <rjw@rjwysocki.net> wrote:
>
> Hi Everyone,
>
> After
>
> https://patchwork.kernel.org/project/linux-acpi/patch/5745568.DvuYhMxLoT@kreacher/
>
> the SCI interrupt handler is threaded, so ACPICA spin locks can be used without
> disabling interrupts, because they cannot be acquired from a hardirq handler
> running on the same CPU as any code already holding the spin lock.  This patch
> [1/3] removes disabling interrupts from acpi_os_acquire_lock() and updates
> acpi_os_release_lock() accordingly.
>
> Patch [2/2] uses the observation that if acpi_handle_interrupt() can run
> in a threaded interrupt handler in the GPE case, it can also run in a threaded
> interrupt handler in the dedicated IRQ case, so it makes the EC driver use a
> threaded handler for the dedicated EC interrupt.
>
> Patch [3/3], in analogy with patch [1/3], uses the observation that after patch
> [2/2] all of the EC code runs in thread context, so it need not disable
> interrupts on the local CPU before acquiring a spin lock, so the EC driver is
> updated to operate its spin lock without disabling interrupts.

I don't see any objections to these patches, so queuing them up for 6.8.

Thanks!