[PATCH v3 08/10] powerpc/opal: Add opal_async_wait_response_interruptible() to opal-async

[Cyril Bur]

This patch adds an _interruptible version of opal_async_wait_response().
This is useful when a long running OPAL call is performed on behalf of a
userspace thread, for example, the opal_flash_{read,write,erase}
functions performed by the powernv-flash MTD driver.

It is foreseeable that these functions would take upwards of two minutes
causing the wait_event() to block long enough to cause hung task
warnings. Furthermore, wait_event_interruptible() is preferable as
otherwise there is no way for signals to stop the process which is going
to be confusing in userspace.

Signed-off-by: Cyril Bur <cyrilbur at gmail.com>
---
 arch/powerpc/include/asm/opal.h             |  2 +
 arch/powerpc/platforms/powernv/opal-async.c | 87 +++++++++++++++++++++++++++--
 2 files changed, 85 insertions(+), 4 deletions(-)

diff --git a/arch/powerpc/include/asm/opal.h b/arch/powerpc/include/asm/opal.h
index 5553ad2f3e53..6e9e53d744f3 100644
--- a/arch/powerpc/include/asm/opal.h
+++ b/arch/powerpc/include/asm/opal.h
@@ -294,6 +294,8 @@ extern void opal_notifier_update_evt(uint64_t evt_mask, uint64_t evt_val);
 extern int opal_async_get_token_interruptible(void);
 extern int opal_async_release_token(int token);
 extern int opal_async_wait_response(uint64_t token, struct opal_msg *msg);
+extern int opal_async_wait_response_interruptible(uint64_t token,
+		struct opal_msg *msg);
 extern int opal_get_sensor_data(u32 sensor_hndl, u32 *sensor_data);
 
 struct rtc_time;
diff --git a/arch/powerpc/platforms/powernv/opal-async.c b/arch/powerpc/platforms/powernv/opal-async.c
index d692372a0363..f6b30cfceb8f 100644
--- a/arch/powerpc/platforms/powernv/opal-async.c
+++ b/arch/powerpc/platforms/powernv/opal-async.c
@@ -26,6 +26,8 @@
 enum opal_async_token_state {
 	ASYNC_TOKEN_FREE,
 	ASYNC_TOKEN_ALLOCATED,
+	ASYNC_TOKEN_DISPATCHED,
+	ASYNC_TOKEN_ABANDONED,
 	ASYNC_TOKEN_COMPLETED
 };
 
@@ -59,8 +61,10 @@ static int __opal_async_get_token(void)
 }
 
 /*
- * Note: If the returned token is used in an opal call and opal returns
- * OPAL_ASYNC_COMPLETION you MUST opal_async_wait_response() before
+ * Note: If the returned token is used in an opal call and opal
+ * returns OPAL_ASYNC_COMPLETION you MUST one of
+ * opal_async_wait_response() or
+ * opal_async_wait_response_interruptible() at least once before
  * calling another other opal_async_* function
  */
 int opal_async_get_token_interruptible(void)
@@ -97,6 +101,16 @@ static int __opal_async_release_token(int token)
 		opal_async_tokens[token].state = ASYNC_TOKEN_FREE;
 		rc = 0;
 		break;
+	/*
+	 * DISPATCHED and ABANDONED tokens must wait for OPAL to
+	 * respond.
+	 * Mark a DISPATCHED token as ABANDONED so that the response
+	 * response handling code knows no one cares and that it can
+	 * free it then.
+	 */
+	case ASYNC_TOKEN_DISPATCHED:
+		opal_async_tokens[token].state = ASYNC_TOKEN_ABANDONED;
+		/* Fall through */
 	default:
 		rc = 1;
 	}
@@ -129,7 +143,11 @@ int opal_async_wait_response(uint64_t token, struct opal_msg *msg)
 		return -EINVAL;
 	}
 
-	/* Wakeup the poller before we wait for events to speed things
+	/*
+	 * There is no need to mark the token as dispatched, wait_event()
+	 * will block until the token completes.
+	 *
+	 * Wakeup the poller before we wait for events to speed things
 	 * up on platforms or simulators where the interrupts aren't
 	 * functional.
 	 */
@@ -142,11 +160,66 @@ int opal_async_wait_response(uint64_t token, struct opal_msg *msg)
 }
 EXPORT_SYMBOL_GPL(opal_async_wait_response);
 
+int opal_async_wait_response_interruptible(uint64_t token, struct opal_msg *msg)
+{
+	unsigned long flags;
+	int ret;
+
+	if (token >= opal_max_async_tokens) {
+		pr_err("%s: Invalid token passed\n", __func__);
+		return -EINVAL;
+	}
+
+	if (!msg) {
+		pr_err("%s: Invalid message pointer passed\n", __func__);
+		return -EINVAL;
+	}
+
+	/*
+	 * The first time this gets called we mark the token as DISPATCHED
+	 * so that if wait_event_interruptible() returns not zero and the
+	 * caller frees the token, we know not to actually free the token
+	 * until the response comes.
+	 *
+	 * Only change if the token is ALLOCATED - it may have been
+	 * completed even before the caller gets around to calling this
+	 * the first time.
+	 *
+	 * There is also a dirty great comment at the token allocation
+	 * function that if the opal call returns OPAL_ASYNC_COMPLETION to
+	 * the caller then the caller *must* call this or the not
+	 * interruptible version before doing anything else with the
+	 * token.
+	 */
+	if (opal_async_tokens[token].state == ASYNC_TOKEN_ALLOCATED) {
+		spin_lock_irqsave(&opal_async_comp_lock, flags);
+		if (opal_async_tokens[token].state == ASYNC_TOKEN_ALLOCATED)
+			opal_async_tokens[token].state = ASYNC_TOKEN_DISPATCHED;
+		spin_unlock_irqrestore(&opal_async_comp_lock, flags);
+	}
+
+	/*
+	 * Wakeup the poller before we wait for events to speed things
+	 * up on platforms or simulators where the interrupts aren't
+	 * functional.
+	 */
+	opal_wake_poller();
+	ret = wait_event_interruptible(opal_async_wait,
+			opal_async_tokens[token].state ==
+			ASYNC_TOKEN_COMPLETED);
+	if (!ret)
+		memcpy(msg, &opal_async_tokens[token].response, sizeof(*msg));
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(opal_async_wait_response_interruptible);
+
 /* Called from interrupt context */
 static int opal_async_comp_event(struct notifier_block *nb,
 		unsigned long msg_type, void *msg)
 {
 	struct opal_msg *comp_msg = msg;
+	enum opal_async_token_state state;
 	unsigned long flags;
 	uint64_t token;
 
@@ -154,11 +227,17 @@ static int opal_async_comp_event(struct notifier_block *nb,
 		return 0;
 
 	token = be64_to_cpu(comp_msg->params[0]);
-	memcpy(&opal_async_tokens[token].response, comp_msg, sizeof(*comp_msg));
 	spin_lock_irqsave(&opal_async_comp_lock, flags);
+	state = opal_async_tokens[token].state;
 	opal_async_tokens[token].state = ASYNC_TOKEN_COMPLETED;
 	spin_unlock_irqrestore(&opal_async_comp_lock, flags);
 
+	if (state == ASYNC_TOKEN_ABANDONED) {
+		/* Free the token, no one else will */
+		opal_async_release_token(token);
+		return 0;
+	}
+	memcpy(&opal_async_tokens[token].response, comp_msg, sizeof(*comp_msg));
 	wake_up(&opal_async_wait);
 
 	return 0;
-- 
2.13.2