linux-kernel - [PATCH] rapidio/tsi721: Convert from tasklet to BH workqueue

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Date: Wed,  3 Apr 2024 16:36:17 +0000
From: Allen Pais <apais@...ux.microsoft.com>
To: linux-kernel@...r.kernel.org
Cc: tj@...nel.org,
	keescook@...omium.org,
	mporter@...nel.crashing.org,
	alex.bou9@...il.com
Subject: [PATCH] rapidio/tsi721: Convert from tasklet to BH workqueue

The only generic interface to execute asynchronously in the BH context is
tasklet; however, it's marked deprecated and has some design flaws. To
replace tasklets, BH workqueue support was recently added. A BH workqueue
behaves similarly to regular workqueues except that the queued work items
are executed in the BH context.

This patch converts drivers/rapidio/* from tasklet to BH workqueue.

Based on the work done by Tejun Heo <tj@...nel.org>
Branch: https://git.kernel.org/pub/scm/linux/kernel/git/tj/wq.git for-6.10

Signed-off-by: Allen Pais <allen.lkml@...il.com>
---
 drivers/rapidio/devices/tsi721.h     |  2 +-
 drivers/rapidio/devices/tsi721_dma.c | 15 +++++++--------
 2 files changed, 8 insertions(+), 9 deletions(-)

diff --git a/drivers/rapidio/devices/tsi721.h b/drivers/rapidio/devices/tsi721.h
index 4f996ce62725..8fd8127d11d1 100644
--- a/drivers/rapidio/devices/tsi721.h
+++ b/drivers/rapidio/devices/tsi721.h
@@ -704,7 +704,7 @@ struct tsi721_bdma_chan {
 	struct tsi721_tx_desc	*active_tx;
 	struct list_head	queue;
 	struct list_head	free_list;
-	struct tasklet_struct	tasklet;
+	struct work_struct	work;
 	bool			active;
 };
 
diff --git a/drivers/rapidio/devices/tsi721_dma.c b/drivers/rapidio/devices/tsi721_dma.c
index f77f75172bdc..f71cbbacca12 100644
--- a/drivers/rapidio/devices/tsi721_dma.c
+++ b/drivers/rapidio/devices/tsi721_dma.c
@@ -278,7 +278,7 @@ void tsi721_bdma_handler(struct tsi721_bdma_chan *bdma_chan)
 	/* Disable BDMA channel interrupts */
 	iowrite32(0, bdma_chan->regs + TSI721_DMAC_INTE);
 	if (bdma_chan->active)
-		tasklet_hi_schedule(&bdma_chan->tasklet);
+		queue_work(system_bh_highpri_wq, &bdma_chan->work);
 }
 
 #ifdef CONFIG_PCI_MSI
@@ -296,7 +296,7 @@ static irqreturn_t tsi721_bdma_msix(int irq, void *ptr)
 	struct tsi721_bdma_chan *bdma_chan = ptr;
 
 	if (bdma_chan->active)
-		tasklet_hi_schedule(&bdma_chan->tasklet);
+		queue_work(system_bh_highpri_wq, &bdma_chan->work);
 	return IRQ_HANDLED;
 }
 #endif /* CONFIG_PCI_MSI */
@@ -568,9 +568,9 @@ static void tsi721_advance_work(struct tsi721_bdma_chan *bdma_chan,
 		  bdma_chan->id);
 }
 
-static void tsi721_dma_tasklet(unsigned long data)
+static void tsi721_dma_work(struct work_struct *t)
 {
-	struct tsi721_bdma_chan *bdma_chan = (struct tsi721_bdma_chan *)data;
+	struct tsi721_bdma_chan *bdma_chan = from_work(bdma_chan, t, work);
 	u32 dmac_int, dmac_sts;
 
 	dmac_int = ioread32(bdma_chan->regs + TSI721_DMAC_INT);
@@ -790,7 +790,7 @@ static void tsi721_free_chan_resources(struct dma_chan *dchan)
 	tsi721_bdma_interrupt_enable(bdma_chan, 0);
 	bdma_chan->active = false;
 	tsi721_sync_dma_irq(bdma_chan);
-	tasklet_kill(&bdma_chan->tasklet);
+	cancel_work_sync(&bdma_chan->work);
 	INIT_LIST_HEAD(&bdma_chan->free_list);
 	kfree(bdma_chan->tx_desc);
 	tsi721_bdma_ch_free(bdma_chan);
@@ -990,8 +990,7 @@ int tsi721_register_dma(struct tsi721_device *priv)
 		INIT_LIST_HEAD(&bdma_chan->queue);
 		INIT_LIST_HEAD(&bdma_chan->free_list);
 
-		tasklet_init(&bdma_chan->tasklet, tsi721_dma_tasklet,
-			     (unsigned long)bdma_chan);
+		INIT_WORK(&bdma_chan->work, tsi721_dma_work);
 		list_add_tail(&bdma_chan->dchan.device_node,
 			      &mport->dma.channels);
 		nr_channels++;
@@ -1033,7 +1032,7 @@ void tsi721_unregister_dma(struct tsi721_device *priv)
 			tsi721_bdma_interrupt_enable(bdma_chan, 0);
 			bdma_chan->active = false;
 			tsi721_sync_dma_irq(bdma_chan);
-			tasklet_kill(&bdma_chan->tasklet);
+			cancel_work_sync(&bdma_chan->work);
 			INIT_LIST_HEAD(&bdma_chan->free_list);
 			kfree(bdma_chan->tx_desc);
 			tsi721_bdma_ch_free(bdma_chan);
-- 
2.17.1