linux-kernel - [PATCH 5.15 702/917] dmaengine: idxd: move out percpu_ref

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Date:   Mon, 15 Nov 2021 18:03:17 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Kevin Tian <kevin.tian@...el.com>,
        Dave Jiang <dave.jiang@...el.com>,
        Vinod Koul <vkoul@...nel.org>, Sasha Levin <sashal@...nel.org>
Subject: [PATCH 5.15 702/917] dmaengine: idxd: move out percpu_ref_exit() to ensure its outside submission

From: Dave Jiang <dave.jiang@...el.com>

[ Upstream commit 85f604af9c83a4656b1d07bec73298c3ba7d7c1e ]

percpu_ref_tryget_live() is safe to call as long as ref is between init and
exit according to the function comment. Move percpu_ref_exit() so it is
called after the dma channel is no longer valid to ensure this holds true.

Fixes: 93a40a6d7428 ("dmaengine: idxd: add percpu_ref to descriptor submission path")
Suggested-by: Kevin Tian <kevin.tian@...el.com>
Signed-off-by: Dave Jiang <dave.jiang@...el.com>
Link: https://lore.kernel.org/r/163294293832.914350.10326422026738506152.stgit@djiang5-desk3.ch.intel.com
Signed-off-by: Vinod Koul <vkoul@...nel.org>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/dma/idxd/device.c | 1 -
 drivers/dma/idxd/dma.c    | 2 ++
 2 files changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/dma/idxd/device.c b/drivers/dma/idxd/device.c
index 83a5ff2ecf2a0..cbbfa17d8d11b 100644
--- a/drivers/dma/idxd/device.c
+++ b/drivers/dma/idxd/device.c
@@ -427,7 +427,6 @@ void idxd_wq_quiesce(struct idxd_wq *wq)
 {
 	percpu_ref_kill(&wq->wq_active);
 	wait_for_completion(&wq->wq_dead);
-	percpu_ref_exit(&wq->wq_active);
 }
 
 /* Device control bits */
diff --git a/drivers/dma/idxd/dma.c b/drivers/dma/idxd/dma.c
index e0f056c1d1f56..b90b085d18cff 100644
--- a/drivers/dma/idxd/dma.c
+++ b/drivers/dma/idxd/dma.c
@@ -311,6 +311,7 @@ static int idxd_dmaengine_drv_probe(struct idxd_dev *idxd_dev)
 
 err_dma:
 	idxd_wq_quiesce(wq);
+	percpu_ref_exit(&wq->wq_active);
 err_ref:
 	idxd_wq_free_resources(wq);
 err_res_alloc:
@@ -329,6 +330,7 @@ static void idxd_dmaengine_drv_remove(struct idxd_dev *idxd_dev)
 	idxd_wq_quiesce(wq);
 	idxd_unregister_dma_channel(wq);
 	__drv_disable_wq(wq);
+	percpu_ref_exit(&wq->wq_active);
 	idxd_wq_free_resources(wq);
 	wq->type = IDXD_WQT_NONE;
 	mutex_unlock(&wq->wq_lock);
-- 
2.33.0