Date: Wed,  3 Apr 2024 14:45:58 +0000
From: Allen Pais <apais@...ux.microsoft.com>
To: linux-kernel@...r.kernel.org
Cc: tj@...nel.org,
	keescook@...omium.org,
	o-takashi@...amocchi.jp,
	linux1394-devel@...ts.sourceforge.net
Subject: [PATCH] firewire: 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/firewire/* 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 disable_work-v1

Changes are tested by: @recallmenot
(https://github.com/allenpais/for-6.9-bh-conversions/issues/1)

Signed-off-by: Allen Pais <allen.lkml@...il.com>
---
 drivers/firewire/ohci.c | 54 ++++++++++++++++++++---------------------
 1 file changed, 26 insertions(+), 28 deletions(-)

diff --git a/drivers/firewire/ohci.c b/drivers/firewire/ohci.c
index 7bc71f4be64a..0c8e73e894e8 100644
--- a/drivers/firewire/ohci.c
+++ b/drivers/firewire/ohci.c
@@ -93,7 +93,7 @@ struct ar_context {
 	void *pointer;
 	unsigned int last_buffer_index;
 	u32 regs;
-	struct tasklet_struct tasklet;
+	struct work_struct work;
 };
 
 struct context;
@@ -150,7 +150,7 @@ struct context {
 
 	descriptor_callback_t callback;
 
-	struct tasklet_struct tasklet;
+	struct work_struct work;
 };
 
 #define IT_HEADER_SY(v)          ((v) <<  0)
@@ -968,9 +968,9 @@ static void ar_recycle_buffers(struct ar_context *ctx, unsigned int end_buffer)
 	}
 }
 
-static void ar_context_tasklet(unsigned long data)
+static void ar_context_work(struct work_struct *w)
 {
-	struct ar_context *ctx = (struct ar_context *)data;
+	struct ar_context *ctx = from_work(ctx, w, work);
 	unsigned int end_buffer_index, end_buffer_offset;
 	void *p, *end;
 
@@ -1025,7 +1025,7 @@ static int ar_context_init(struct ar_context *ctx, struct fw_ohci *ohci,
 
 	ctx->regs        = regs;
 	ctx->ohci        = ohci;
-	tasklet_init(&ctx->tasklet, ar_context_tasklet, (unsigned long)ctx);
+	INIT_WORK(&ctx->work, ar_context_work);
 
 	for (i = 0; i < AR_BUFFERS; i++) {
 		ctx->pages[i] = dma_alloc_pages(dev, PAGE_SIZE, &dma_addr,
@@ -1093,9 +1093,9 @@ static struct descriptor *find_branch_descriptor(struct descriptor *d, int z)
 		return d + z - 1;
 }
 
-static void context_tasklet(unsigned long data)
+static void context_work(struct work_struct *w)
 {
-	struct context *ctx = (struct context *) data;
+	struct context *ctx = from_work(ctx, w, work);
 	struct descriptor *d, *last;
 	u32 address;
 	int z;
@@ -1188,7 +1188,7 @@ static int context_init(struct context *ctx, struct fw_ohci *ohci,
 	ctx->buffer_tail = list_entry(ctx->buffer_list.next,
 			struct descriptor_buffer, list);
 
-	tasklet_init(&ctx->tasklet, context_tasklet, (unsigned long)ctx);
+	INIT_WORK(&ctx->work, context_work);
 	ctx->callback = callback;
 
 	/*
@@ -1460,13 +1460,12 @@ static int at_context_queue_packet(struct context *ctx,
 
 static void at_context_flush(struct context *ctx)
 {
-	tasklet_disable(&ctx->tasklet);
+	disable_work_sync(&ctx->work);
 
 	ctx->flushing = true;
-	context_tasklet((unsigned long)ctx);
 	ctx->flushing = false;
 
-	tasklet_enable(&ctx->tasklet);
+	enable_and_queue_work(system_bh_wq, &ctx->work);
 }
 
 static int handle_at_packet(struct context *context,
@@ -2136,16 +2135,16 @@ static irqreturn_t irq_handler(int irq, void *data)
 		queue_work(selfid_workqueue, &ohci->bus_reset_work);
 
 	if (event & OHCI1394_RQPkt)
-		tasklet_schedule(&ohci->ar_request_ctx.tasklet);
+		queue_work(system_bh_wq, &ohci->ar_request_ctx.work);
 
 	if (event & OHCI1394_RSPkt)
-		tasklet_schedule(&ohci->ar_response_ctx.tasklet);
+		queue_work(system_bh_wq, &ohci->ar_response_ctx.work);
 
 	if (event & OHCI1394_reqTxComplete)
-		tasklet_schedule(&ohci->at_request_ctx.tasklet);
+		queue_work(system_bh_wq, &ohci->at_request_ctx.work);
 
 	if (event & OHCI1394_respTxComplete)
-		tasklet_schedule(&ohci->at_response_ctx.tasklet);
+		queue_work(system_bh_wq, &ohci->at_response_ctx.work);
 
 	if (event & OHCI1394_isochRx) {
 		iso_event = reg_read(ohci, OHCI1394_IsoRecvIntEventClear);
@@ -2153,8 +2152,8 @@ static irqreturn_t irq_handler(int irq, void *data)
 
 		while (iso_event) {
 			i = ffs(iso_event) - 1;
-			tasklet_schedule(
-				&ohci->ir_context_list[i].context.tasklet);
+			queue_work(system_bh_wq,
+				&ohci->ir_context_list[i].context.work);
 			iso_event &= ~(1 << i);
 		}
 	}
@@ -2165,8 +2164,8 @@ static irqreturn_t irq_handler(int irq, void *data)
 
 		while (iso_event) {
 			i = ffs(iso_event) - 1;
-			tasklet_schedule(
-				&ohci->it_context_list[i].context.tasklet);
+			queue_work(system_bh_wq,
+				&ohci->it_context_list[i].context.work);
 			iso_event &= ~(1 << i);
 		}
 	}
@@ -2431,7 +2430,7 @@ static int ohci_enable(struct fw_card *card,
 	 * They shouldn't do that in this initial case where the link
 	 * isn't enabled.  This means we have to use the same
 	 * workaround here, setting the bus header to 0 and then write
-	 * the right values in the bus reset tasklet.
+	 * the right values in the bus reset work.
 	 */
 
 	if (config_rom) {
@@ -2521,7 +2520,7 @@ static int ohci_set_config_rom(struct fw_card *card,
 	 * during the atomic update, even on litte endian
 	 * architectures.  The workaround we use is to put a 0 in the
 	 * header quadlet; 0 is endian agnostic and means that the
-	 * config rom isn't ready yet.  In the bus reset tasklet we
+	 * config rom isn't ready yet.  In the bus reset work we
 	 * then set up the real values for the two registers.
 	 *
 	 * We use ohci->lock to avoid racing with the code that sets
@@ -2570,7 +2569,7 @@ static int ohci_set_config_rom(struct fw_card *card,
 	/*
 	 * Now initiate a bus reset to have the changes take
 	 * effect. We clean up the old config rom memory and DMA
-	 * mappings in the bus reset tasklet, since the OHCI
+	 * mappings in the bus reset work, since the OHCI
 	 * controller could need to access it before the bus reset
 	 * takes effect.
 	 */
@@ -2601,7 +2600,7 @@ static int ohci_cancel_packet(struct fw_card *card, struct fw_packet *packet)
 	struct driver_data *driver_data = packet->driver_data;
 	int ret = -ENOENT;
 
-	tasklet_disable_in_atomic(&ctx->tasklet);
+	disable_work_sync(&ctx->work);
 
 	if (packet->ack != 0)
 		goto out;
@@ -2620,7 +2619,7 @@ static int ohci_cancel_packet(struct fw_card *card, struct fw_packet *packet)
 	packet->callback(packet, &ohci->card, packet->ack);
 	ret = 0;
  out:
-	tasklet_enable(&ctx->tasklet);
+	enable_and_queue_work(system_bh_wq, &ctx->work);
 
 	return ret;
 }
@@ -3153,7 +3152,7 @@ static int ohci_stop_iso(struct fw_iso_context *base)
 	}
 	flush_writes(ohci);
 	context_stop(&ctx->context);
-	tasklet_kill(&ctx->context.tasklet);
+	cancel_work_sync(&ctx->context.work);
 
 	return 0;
 }
@@ -3525,10 +3524,9 @@ static int ohci_flush_iso_completions(struct fw_iso_context *base)
 	struct iso_context *ctx = container_of(base, struct iso_context, base);
 	int ret = 0;
 
-	tasklet_disable_in_atomic(&ctx->context.tasklet);
+	disable_work_sync(&ctx->context.work);
 
 	if (!test_and_set_bit_lock(0, &ctx->flushing_completions)) {
-		context_tasklet((unsigned long)&ctx->context);
 
 		switch (base->type) {
 		case FW_ISO_CONTEXT_TRANSMIT:
@@ -3548,7 +3546,7 @@ static int ohci_flush_iso_completions(struct fw_iso_context *base)
 		smp_mb__after_atomic();
 	}
 
-	tasklet_enable(&ctx->context.tasklet);
+	enable_and_queue_work(system_bh_wq, &ctx->context.work);
 
 	return ret;
 }
-- 
2.17.1

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