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From:   Oded Gabbay <oded.gabbay@gmail.com>
To:     linux-kernel@vger.kernel.org, oshpigelman@habana.ai,
        ttayar@habana.ai
Cc:     gregkh@linuxfoundation.org
Subject: [PATCH] habanalabs: rate limit error msg on waiting for CS
Date:   Tue,  3 Dec 2019 22:27:50 +0200
Message-Id: <20191203202750.9498-1-oded.gabbay@gmail.com>
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

In case a user submits a CS, and the submission fails, and the user doesn't
check the return value and instead use the error return value as a valid
sequence number of a CS and ask to wait on it, the driver will print an
error and return an error code for that wait.

The real problem happens if now the user ignores the error of the wait, and
try to wait again and again. This can lead to a flood of error messages
from the driver and even soft lockup event.

Signed-off-by: Oded Gabbay <oded.gabbay@gmail.com>
---
 drivers/misc/habanalabs/command_submission.c | 5 +++--
 drivers/misc/habanalabs/context.c            | 2 +-
 2 files changed, 4 insertions(+), 3 deletions(-)

diff --git a/drivers/misc/habanalabs/command_submission.c b/drivers/misc/habanalabs/command_submission.c
index 8850f475a413..0bf08678431b 100644
--- a/drivers/misc/habanalabs/command_submission.c
+++ b/drivers/misc/habanalabs/command_submission.c
@@ -824,8 +824,9 @@ int hl_cs_wait_ioctl(struct hl_fpriv *hpriv, void *data)
 	memset(args, 0, sizeof(*args));
 
 	if (rc < 0) {
-		dev_err(hdev->dev, "Error %ld on waiting for CS handle %llu\n",
-			rc, seq);
+		dev_err_ratelimited(hdev->dev,
+				"Error %ld on waiting for CS handle %llu\n",
+				rc, seq);
 		if (rc == -ERESTARTSYS) {
 			args->out.status = HL_WAIT_CS_STATUS_INTERRUPTED;
 			rc = -EINTR;
diff --git a/drivers/misc/habanalabs/context.c b/drivers/misc/habanalabs/context.c
index 17db7b3dfb4c..2df6fb87e7ff 100644
--- a/drivers/misc/habanalabs/context.c
+++ b/drivers/misc/habanalabs/context.c
@@ -176,7 +176,7 @@ struct dma_fence *hl_ctx_get_fence(struct hl_ctx *ctx, u64 seq)
 	spin_lock(&ctx->cs_lock);
 
 	if (seq >= ctx->cs_sequence) {
-		dev_notice(hdev->dev,
+		dev_notice_ratelimited(hdev->dev,
 			"Can't wait on seq %llu because current CS is at seq %llu\n",
 			seq, ctx->cs_sequence);
 		spin_unlock(&ctx->cs_lock);
-- 
2.17.1