linux-kernel - [PATCH 10/11] drivers/misc/vmw_vmci: convert num guest devices counter to counter

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Message-Id: <df6cafabdf2fe3a0e954be24ad5015c4d95605a4.1601073127.git.skhan@linuxfoundation.org>
Date:   Fri, 25 Sep 2020 17:47:24 -0600
From:   Shuah Khan <skhan@...uxfoundation.org>
To:     arnd@...db.de, gregkh@...uxfoundation.org, keescook@...omium.org
Cc:     Shuah Khan <skhan@...uxfoundation.org>,
        linux-kernel@...r.kernel.org
Subject: [PATCH 10/11] drivers/misc/vmw_vmci: convert num guest devices counter to counter_atomic32

counter_atomic* is introduced to be used when a variable is used as
a simple counter and doesn't guard object lifetimes. This clearly
differentiates atomic_t usages that guard object lifetimes.

counter_atomic* variables will wrap around to 0 when it overflows and
should not be used to guard resource lifetimes, device usage and
open counts that control state changes, and pm states.

atomic_t variable used to count number of vmci guest devices is used
as just as counter and it doesn't control object lifetimes or state
management. Overflow doesn't appear to be problem for this use.

Convert it to use counter_atomic32.

This conversion doesn't change the overflow wrap around behavior.

Reviewed-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Signed-off-by: Shuah Khan <skhan@...uxfoundation.org>
---
 drivers/misc/vmw_vmci/vmci_guest.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/drivers/misc/vmw_vmci/vmci_guest.c b/drivers/misc/vmw_vmci/vmci_guest.c
index cc8eeb361fcd..86ae27b05fc2 100644
--- a/drivers/misc/vmw_vmci/vmci_guest.c
+++ b/drivers/misc/vmw_vmci/vmci_guest.c
@@ -20,6 +20,7 @@
 #include <linux/smp.h>
 #include <linux/io.h>
 #include <linux/vmalloc.h>
+#include <linux/counters.h>
 
 #include "vmci_datagram.h"
 #include "vmci_doorbell.h"
@@ -68,11 +69,11 @@ struct pci_dev *vmci_pdev;
 static struct vmci_guest_device *vmci_dev_g;
 static DEFINE_SPINLOCK(vmci_dev_spinlock);
 
-static atomic_t vmci_num_guest_devices = ATOMIC_INIT(0);
+static struct counter_atomic32 vmci_num_guest_devices = COUNTER_ATOMIC_INIT(0);
 
 bool vmci_guest_code_active(void)
 {
-	return atomic_read(&vmci_num_guest_devices) != 0;
+	return counter_atomic32_read(&vmci_num_guest_devices) != 0;
 }
 
 u32 vmci_get_vm_context_id(void)
@@ -624,7 +625,7 @@ static int vmci_guest_probe_device(struct pci_dev *pdev,
 
 	dev_dbg(&pdev->dev, "Registered device\n");
 
-	atomic_inc(&vmci_num_guest_devices);
+	counter_atomic32_inc(&vmci_num_guest_devices);
 
 	/* Enable specific interrupt bits. */
 	cmd = VMCI_IMR_DATAGRAM;
@@ -684,7 +685,7 @@ static void vmci_guest_remove_device(struct pci_dev *pdev)
 
 	dev_dbg(&pdev->dev, "Removing device\n");
 
-	atomic_dec(&vmci_num_guest_devices);
+	counter_atomic32_dec(&vmci_num_guest_devices);
 
 	vmci_qp_guest_endpoints_exit();
 
-- 
2.25.1