linux-kernel - [PATCH v9 12/13] powerpc/vas: Display process stuck message

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Date:   Wed, 01 Apr 2020 14:31:34 -0700
From:   Haren Myneni <haren@...ux.ibm.com>
To:     mpe@...erman.id.au
Cc:     npiggin@...il.com, mikey@...ling.org, herbert@...dor.apana.org.au,
        frederic.barrat@...ibm.com, srikar@...ux.vnet.ibm.com,
        linux-kernel@...r.kernel.org, hch@...radead.org, oohall@...il.com,
        clg@...d.org, sukadev@...ux.vnet.ibm.com,
        linuxppc-dev@...ts.ozlabs.org, ajd@...ux.ibm.com
Subject: [PATCH v9 12/13] powerpc/vas: Display process stuck message


Process can not close send window until all requests are processed.
Means wait until window state is not busy and send credits are
returned. Display debug messages in case taking longer to close the
window.

Signed-off-by: Haren Myneni <haren@...ux.ibm.com>
---
 arch/powerpc/platforms/powernv/vas-window.c | 28 ++++++++++++++++++++++++++++
 1 file changed, 28 insertions(+)

diff --git a/arch/powerpc/platforms/powernv/vas-window.c b/arch/powerpc/platforms/powernv/vas-window.c
index 084e76b..c8644c3 100644
--- a/arch/powerpc/platforms/powernv/vas-window.c
+++ b/arch/powerpc/platforms/powernv/vas-window.c
@@ -1182,6 +1182,7 @@ static void poll_window_credits(struct vas_window *window)
 {
 	u64 val;
 	int creds, mode;
+	int count = 0;
 
 	val = read_hvwc_reg(window, VREG(WINCTL));
 	if (window->tx_win)
@@ -1200,10 +1201,27 @@ static void poll_window_credits(struct vas_window *window)
 		creds = GET_FIELD(VAS_LRX_WCRED, val);
 	}
 
+	/*
+	 * Takes around few milliseconds to complete all pending requests
+	 * and return credits.
+	 * TODO: Scan fault FIFO and invalidate CRBs points to this window
+	 *       and issue CRB Kill to stop all pending requests. Need only
+	 *       if there is a bug in NX or fault handling in kernel.
+	 */
 	if (creds < window->wcreds_max) {
 		val = 0;
 		set_current_state(TASK_UNINTERRUPTIBLE);
 		schedule_timeout(msecs_to_jiffies(10));
+		count++;
+		/*
+		 * Process can not close send window until all credits are
+		 * returned.
+		 */
+		if (!(count % 10000))
+			pr_debug("VAS: pid %d stuck. Waiting for credits returned for Window(%d). creds %d, Retries %d\n",
+				vas_window_pid(window), window->winid,
+				creds, count);
+
 		goto retry;
 	}
 }
@@ -1217,6 +1235,7 @@ static void poll_window_busy_state(struct vas_window *window)
 {
 	int busy;
 	u64 val;
+	int count = 0;
 
 retry:
 	val = read_hvwc_reg(window, VREG(WIN_STATUS));
@@ -1225,6 +1244,15 @@ static void poll_window_busy_state(struct vas_window *window)
 		val = 0;
 		set_current_state(TASK_UNINTERRUPTIBLE);
 		schedule_timeout(msecs_to_jiffies(5));
+		count++;
+		/*
+		 * Takes around few milliseconds to process all pending
+		 * requests.
+		 */
+		if (!(count % 10000))
+			pr_debug("VAS: pid %d stuck. Window (ID=%d) is in busy state. Retries %d\n",
+				vas_window_pid(window), window->winid, count);
+
 		goto retry;
 	}
 }
-- 
1.8.3.1