linux-kernel - [PATCH 2/2] habanalabs: flush EQ workers in hard reset

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Message-Id: <20191117192620.27639-2-oded.gabbay@gmail.com>
Date:   Sun, 17 Nov 2019 21:26:20 +0200
From:   Oded Gabbay <oded.gabbay@...il.com>
To:     linux-kernel@...r.kernel.org, oshpigelman@...ana.ai,
        ttayar@...ana.ai
Cc:     gregkh@...uxfoundation.org
Subject: [PATCH 2/2] habanalabs: flush EQ workers in hard reset

During hard-reset, there can be multiple events received from the H/W. For
each event, the driver opens a worker thread to handle it. For some of the
events, the driver will read/write registers in the code that handles the
event.

In case of hard-reset, we must prevent reads/writes to the registers during
the reset operation because the device might get stuck if that happens.

Therefore, flush the EQ workers before resetting the device (in hard-reset
only). Additional events won't arrive as we synced and disabled the
interrupts.

Signed-off-by: Oded Gabbay <oded.gabbay@...il.com>
Reviewed-by: Tomer Tayar <ttayar@...ana.ai>
---
 drivers/misc/habanalabs/device.c | 16 +++++++++++-----
 1 file changed, 11 insertions(+), 5 deletions(-)

diff --git a/drivers/misc/habanalabs/device.c b/drivers/misc/habanalabs/device.c
index 80205d8584ce..b155e9549076 100644
--- a/drivers/misc/habanalabs/device.c
+++ b/drivers/misc/habanalabs/device.c
@@ -887,13 +887,19 @@ int hl_device_reset(struct hl_device *hdev, bool hard_reset,
 	/* Go over all the queues, release all CS and their jobs */
 	hl_cs_rollback_all(hdev);
 
-	/* Kill processes here after CS rollback. This is because the process
-	 * can't really exit until all its CSs are done, which is what we
-	 * do in cs rollback
-	 */
-	if (hard_reset)
+	if (hard_reset) {
+		/* Kill processes here after CS rollback. This is because the
+		 * process can't really exit until all its CSs are done, which
+		 * is what we do in cs rollback
+		 */
 		device_kill_open_processes(hdev);
 
+		/* Flush the Event queue workers to make sure no other thread is
+		 * reading or writing to registers during the reset
+		 */
+		flush_workqueue(hdev->eq_wq);
+	}
+
 	/* Release kernel context */
 	if ((hard_reset) && (hl_ctx_put(hdev->kernel_ctx) == 1))
 		hdev->kernel_ctx = NULL;
-- 
2.17.1