From: Greg KH <gregkh@linuxfoundation.org>
To: Shuah Khan <skhan@linuxfoundation.org>
Cc: arnd@arndb.de, keescook@chromium.org, linux-kernel@vger.kernel.org
Subject: Re: [RFC PATCH 10/11] drivers/misc/vmw_vmci: convert num guest devices counter to counter_atomic
Date: Wed, 23 Sep 2020 12:29:57 +0200 [thread overview]
Message-ID: <20200923102957.GF3154647@kroah.com> (raw)
In-Reply-To: <e53dcdeb280bd90e074f214f8f292e89dedb36df.1600816121.git.skhan@linuxfoundation.org>
On Tue, Sep 22, 2020 at 07:43:39PM -0600, Shuah Khan wrote:
> 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_atomic.
>
> This conversion doesn't change the oveflow wrap around behavior.
>
> Signed-off-by: Shuah Khan <skhan@linuxfoundation.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..2c21448af730 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_atomic vmci_num_guest_devices = COUNTER_ATOMIC_INIT(0);
>
> bool vmci_guest_code_active(void)
> {
> - return atomic_read(&vmci_num_guest_devices) != 0;
> + return counter_atomic_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_atomic_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_atomic_dec(&vmci_num_guest_devices);
>
> vmci_qp_guest_endpoints_exit();
>
While this conversion looks fine to me, wow, the code does not really
seem to be doing the right thing. So that's something to fix up
independantly of this change, not your fault at all :)
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
next prev parent reply other threads:[~2020-09-23 10:29 UTC|newest]
Thread overview: 31+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-09-23 1:43 [RFC PATCH 00/11] Introduce Simple atomic and non-atomic counters Shuah Khan
2020-09-23 1:43 ` [RFC PATCH 01/11] counters: Introduce counter and counter_atomic Shuah Khan
2020-09-23 10:35 ` Greg KH
2020-09-23 19:04 ` Kees Cook
2020-09-23 19:34 ` Greg KH
2020-09-23 20:54 ` Kees Cook
2020-09-23 20:48 ` Shuah Khan
2020-09-23 20:58 ` Kees Cook
2020-09-23 21:19 ` Shuah Khan
2020-09-23 22:04 ` Kees Cook
2020-09-23 1:43 ` [RFC PATCH 02/11] selftests:lib: add new test for counters Shuah Khan
2020-09-23 1:43 ` [RFC PATCH 03/11] drivers/base: convert deferred_trigger_count and probe_count to counter_atomic Shuah Khan
2020-09-23 10:30 ` Greg KH
2020-09-23 1:43 ` [RFC PATCH 04/11] drivers/base/devcoredump: convert devcd_count " Shuah Khan
2020-09-23 10:31 ` Greg KH
2020-09-23 1:43 ` [RFC PATCH 05/11] drivers/acpi: convert seqno counter_atomic Shuah Khan
2020-09-24 11:13 ` Rafael J. Wysocki
2020-09-24 15:08 ` Shuah Khan
2020-09-24 15:32 ` Rafael J. Wysocki
2020-09-23 1:43 ` [RFC PATCH 06/11] drivers/acpi/apei: " Shuah Khan
2020-09-23 1:43 ` [RFC PATCH 07/11] drivers/android/binder: convert stats, transaction_log to counter_atomic Shuah Khan
2020-09-23 5:10 ` Greg KH
2020-09-23 19:04 ` Kees Cook
2020-09-23 19:31 ` Greg KH
2020-09-23 20:51 ` Kees Cook
2020-09-23 1:43 ` [RFC PATCH 08/11] drivers/base/test/test_async_driver_probe: convert to use counter_atomic Shuah Khan
2020-09-23 10:33 ` Greg KH
2020-09-23 1:43 ` [RFC PATCH 09/11] drivers/char/ipmi: convert stats " Shuah Khan
2020-09-23 1:43 ` [RFC PATCH 10/11] drivers/misc/vmw_vmci: convert num guest devices counter to counter_atomic Shuah Khan
2020-09-23 10:29 ` Greg KH [this message]
2020-09-23 1:43 ` [RFC PATCH 11/11] drivers/edac: convert pci counters " Shuah Khan
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