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From: Mitchell Levy via B4 Relay  <devnull+levymitchell0.gmail.com@kernel.org>
To: "K. Y. Srinivasan" <kys@microsoft.com>,
	"Haiyang Zhang" <haiyangz@microsoft.com>,
	"Wei Liu" <wei.liu@kernel.org>,
	"Dexuan Cui" <decui@microsoft.com>,
	"Lorenzo Pieralisi" <lpieralisi@kernel.org>,
	"Krzysztof Wilczyński" <kw@linux.com>,
	"Rob Herring" <robh@kernel.org>,
	"Bjorn Helgaas" <bhelgaas@google.com>
Cc: linux-hyperv@vger.kernel.org, linux-kernel@vger.kernel.org,
	linux-pci@vger.kernel.org,
	Mitchell Levy <levymitchell0@gmail.com>
Subject: [PATCH RFC 1/2] Use raw_spinlock_t for vmbus_channel.sched_lock
Date: Wed, 09 Aug 2023 22:36:32 +0000	[thread overview]
Message-ID: <20230809-b4-rt_preempt-fix-v1-1-7283bbdc8b14@gmail.com> (raw)
In-Reply-To: <20230809-b4-rt_preempt-fix-v1-0-7283bbdc8b14@gmail.com>

From: Mitchell Levy <levymitchell0@gmail.com>

In vmbus_drv.c, vmbus_channel.sched_lock is acquired while holding an
rcu_read_lock. Since this is not a sleepable context, change sched_lock
to be a raw_spinlock_t to avoid sleeping when PREEMPT_RT is enabled.
---
 drivers/hv/channel.c                | 4 ++--
 drivers/hv/channel_mgmt.c           | 2 +-
 drivers/hv/vmbus_drv.c              | 4 ++--
 drivers/pci/controller/pci-hyperv.c | 6 +++---
 include/linux/hyperv.h              | 2 +-
 5 files changed, 9 insertions(+), 9 deletions(-)

diff --git a/drivers/hv/channel.c b/drivers/hv/channel.c
index 56f7e06c673e..00d73ec060ed 100644
--- a/drivers/hv/channel.c
+++ b/drivers/hv/channel.c
@@ -910,9 +910,9 @@ void vmbus_reset_channel_cb(struct vmbus_channel *channel)
 	tasklet_disable(&channel->callback_event);
 
 	/* See the inline comments in vmbus_chan_sched(). */
-	spin_lock_irqsave(&channel->sched_lock, flags);
+	raw_spin_lock_irqsave(&channel->sched_lock, flags);
 	channel->onchannel_callback = NULL;
-	spin_unlock_irqrestore(&channel->sched_lock, flags);
+	raw_spin_unlock_irqrestore(&channel->sched_lock, flags);
 
 	channel->sc_creation_callback = NULL;
 
diff --git a/drivers/hv/channel_mgmt.c b/drivers/hv/channel_mgmt.c
index 2f4d09ce027a..7679e6a3a645 100644
--- a/drivers/hv/channel_mgmt.c
+++ b/drivers/hv/channel_mgmt.c
@@ -348,7 +348,7 @@ static struct vmbus_channel *alloc_channel(void)
 	if (!channel)
 		return NULL;
 
-	spin_lock_init(&channel->sched_lock);
+	raw_spin_lock_init(&channel->sched_lock);
 	init_completion(&channel->rescind_event);
 
 	INIT_LIST_HEAD(&channel->sc_list);
diff --git a/drivers/hv/vmbus_drv.c b/drivers/hv/vmbus_drv.c
index 67f95a29aeca..b865d00c46dc 100644
--- a/drivers/hv/vmbus_drv.c
+++ b/drivers/hv/vmbus_drv.c
@@ -1257,7 +1257,7 @@ static void vmbus_chan_sched(struct hv_per_cpu_context *hv_cpu)
 		 * sched_lock critical section.  See also the inline comments
 		 * in vmbus_reset_channel_cb().
 		 */
-		spin_lock(&channel->sched_lock);
+		raw_spin_lock(&channel->sched_lock);
 
 		callback_fn = channel->onchannel_callback;
 		if (unlikely(callback_fn == NULL))
@@ -1280,7 +1280,7 @@ static void vmbus_chan_sched(struct hv_per_cpu_context *hv_cpu)
 		}
 
 sched_unlock:
-		spin_unlock(&channel->sched_lock);
+		raw_spin_unlock(&channel->sched_lock);
 sched_unlock_rcu:
 		rcu_read_unlock();
 	}
diff --git a/drivers/pci/controller/pci-hyperv.c b/drivers/pci/controller/pci-hyperv.c
index 2d93d0c4f10d..9ede3be05782 100644
--- a/drivers/pci/controller/pci-hyperv.c
+++ b/drivers/pci/controller/pci-hyperv.c
@@ -1995,13 +1995,13 @@ static void hv_compose_msi_msg(struct irq_data *data, struct msi_msg *msg)
 		 * sched_lock critical section.  See also the inline comments
 		 * in vmbus_reset_channel_cb().
 		 */
-		spin_lock_irqsave(&channel->sched_lock, flags);
+		raw_spin_lock_irqsave(&channel->sched_lock, flags);
 		if (unlikely(channel->onchannel_callback == NULL)) {
-			spin_unlock_irqrestore(&channel->sched_lock, flags);
+			raw_spin_unlock_irqrestore(&channel->sched_lock, flags);
 			goto enable_tasklet;
 		}
 		hv_pci_onchannelcallback(hbus);
-		spin_unlock_irqrestore(&channel->sched_lock, flags);
+		raw_spin_unlock_irqrestore(&channel->sched_lock, flags);
 
 		udelay(100);
 	}
diff --git a/include/linux/hyperv.h b/include/linux/hyperv.h
index 3ac3974b3c78..56a1fb1647a4 100644
--- a/include/linux/hyperv.h
+++ b/include/linux/hyperv.h
@@ -873,7 +873,7 @@ struct vmbus_channel {
 	 * Synchronize channel scheduling and channel removal; see the inline
 	 * comments in vmbus_chan_sched() and vmbus_reset_channel_cb().
 	 */
-	spinlock_t sched_lock;
+	raw_spinlock_t sched_lock;
 
 	/*
 	 * A channel can be marked for one of three modes of reading:

-- 
2.25.1


  reply	other threads:[~2023-08-09 22:36 UTC|newest]

Thread overview: 4+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2023-08-09 22:36 [PATCH RFC 0/2] hyperv: Use raw_spinlock_t when not sleepable Mitchell Levy via B4 Relay
2023-08-09 22:36 ` Mitchell Levy via B4 Relay [this message]
2023-08-09 22:36 ` [PATCH RFC 2/2] Use raw_spinlock_t in vmbus_requestor Mitchell Levy via B4 Relay
2023-08-15 18:44 ` [PATCH RFC 0/2] hyperv: Use raw_spinlock_t when not sleepable Michael Kelley (LINUX)

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