linux-kernel - [PATCH v2 2/2] PCI: hv: Convert from tasklet to BH workqueue

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Date: Wed,  3 Apr 2024 16:55:42 +0000
From: Allen Pais <apais@...ux.microsoft.com>
To: linux-kernel@...r.kernel.org
Cc: tj@...nel.org,
	keescook@...omium.org,
	kys@...rosoft.com,
	haiyangz@...rosoft.com,
	wei.liu@...nel.org,
	decui@...rosoft.com,
	linux-hyperv@...r.kernel.org
Subject: [PATCH v2 2/2] PCI: hv: 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/pci/pci-hyperv.c 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/pci/controller/pci-hyperv.c | 13 +++++++------
 1 file changed, 7 insertions(+), 6 deletions(-)

diff --git a/drivers/pci/controller/pci-hyperv.c b/drivers/pci/controller/pci-hyperv.c
index 5992280e8110..2823fd50a69c 100644
--- a/drivers/pci/controller/pci-hyperv.c
+++ b/drivers/pci/controller/pci-hyperv.c
@@ -50,6 +50,7 @@
 #include <linux/irqdomain.h>
 #include <linux/acpi.h>
 #include <linux/sizes.h>
+#include <linux/workqueue.h>
 #include <asm/mshyperv.h>
 
 /*
@@ -2000,7 +2001,7 @@ static void hv_compose_msi_msg(struct irq_data *data, struct msi_msg *msg)
 		udelay(100);
 	}
 
-	tasklet_enable(&channel->callback_event);
+	enable_and_queue_work(system_bh_wq, &channel->callback_event);
 
 	if (comp.comp_pkt.completion_status < 0) {
 		dev_err(&hbus->hdev->device,
@@ -2026,7 +2027,7 @@ static void hv_compose_msi_msg(struct irq_data *data, struct msi_msg *msg)
 	return;
 
 enable_tasklet:
-	tasklet_enable(&channel->callback_event);
+	enable_and_queue_work(system_bh_wq, &channel->callback_event);
 	/*
 	 * The completion packet on the stack becomes invalid after 'return';
 	 * remove the ID from the VMbus requestor if the identifier is still
@@ -3890,9 +3891,9 @@ static void hv_pci_remove(struct hv_device *hdev)
 
 	hbus = hv_get_drvdata(hdev);
 	if (hbus->state == hv_pcibus_installed) {
-		tasklet_disable(&hdev->channel->callback_event);
+		disable_work_sync(&hdev->channel->callback_event);
 		hbus->state = hv_pcibus_removing;
-		tasklet_enable(&hdev->channel->callback_event);
+		enable_and_queue_work(system_bh_wq, &hdev->channel->callback_event);
 		destroy_workqueue(hbus->wq);
 		hbus->wq = NULL;
 		/*
@@ -3948,14 +3949,14 @@ static int hv_pci_suspend(struct hv_device *hdev)
 	 * it knows that no new work item can be scheduled, and then it flushes
 	 * hbus->wq and safely closes the vmbus channel.
 	 */
-	tasklet_disable(&hdev->channel->callback_event);
+	disable_work_sync(&hdev->channel->callback_event);
 
 	/* Change the hbus state to prevent new work items. */
 	old_state = hbus->state;
 	if (hbus->state == hv_pcibus_installed)
 		hbus->state = hv_pcibus_removing;
 
-	tasklet_enable(&hdev->channel->callback_event);
+	enable_and_queue_work(system_bh_wq, &hdev->channel->callback_event);
 
 	if (old_state != hv_pcibus_installed)
 		return -EINVAL;
-- 
2.17.1