[nrf fromtree] pm: device_runtime: Fix managing the device from multiple contexts

Add early exist to the suspend function if suspending client is
not the last one. It fixes the case where user calls put function
from the thread context and it gets interrupted by the device
interrupt where another asynchronous put is called. In that case,
in the interrupt context the call will return error as semaphore
cannot be taken and reference counting gets broken. By adding
an early exit if context is not the last one, we ensure that only
last client executes suspending procedure.

Signed-off-by: Krzysztof Chruściński <krzysztof.chruscinski@nordicsemi.no>
(cherry picked from commit 46e5ba3732f48ee9a903239a854079fc04f7b3fa)

Author: nordic-krch

subsys/pm/device_runtime.c

@@ -21,6 +21,7 @@ LOG_MODULE_DECLARE(pm_device, CONFIG_PM_DEVICE_LOG_LEVEL);
 #define PM_DOMAIN(_pm) NULL
 #endif
 
+static struct k_spinlock lock;
 #ifdef CONFIG_PM_DEVICE_RUNTIME_ASYNC
 #ifdef CONFIG_PM_DEVICE_RUNTIME_USE_DEDICATED_WQ
 K_THREAD_STACK_DEFINE(pm_device_runtime_stack, CONFIG_PM_DEVICE_RUNTIME_DEDICATED_WQ_STACK_SIZE);
@@ -57,6 +58,7 @@ static int runtime_suspend(const struct device *dev, bool async,
 {
 	int ret = 0;
 	struct pm_device *pm = dev->pm;
+	bool early_exit = false;
 
 	/*
 	 * Early return if device runtime is not enabled.
@@ -65,6 +67,18 @@ static int runtime_suspend(const struct device *dev, bool async,
 		return 0;
 	}
 
+	K_SPINLOCK(&lock) {
+		/* If we are not the last user, return. */
+		if (pm->base.usage > 1U) {
+			pm->base.usage--;
+			early_exit = true;
+		}
+	}
+
+	if (early_exit == true) {
+		return 0;
+	}
+
 	if (k_is_pre_kernel()) {
 		async = false;
 	} else {
@@ -219,6 +233,21 @@ int pm_device_runtime_get(const struct device *dev)
 	}
 
 	if (!k_is_pre_kernel()) {
+		bool early_exit = false;
+
+		K_SPINLOCK(&lock) {
+			/* If we are not the first user and device is active, return. */
+			if ((pm->base.usage > 0U) && (pm->base.state == PM_DEVICE_STATE_ACTIVE)) {
+				pm->base.usage++;
+				early_exit = true;
+			}
+		}
+
+		if (early_exit == true) {
+			ret = 0;
+			goto end;
+		}
+
 		ret = k_sem_take(&pm->lock, k_is_in_isr() ? K_NO_WAIT : K_FOREVER);
 		if (ret < 0) {
 			return -EWOULDBLOCK;