RE: [PATCH 2/2] pci: host: pci-hyperv: Replace GFP_ATOMIC with GFP_KERNEL in new_pcichild_device

[Michael Kelley (EOSG)]

> -----Original Message-----
> From: linux-kernel-owner@xxxxxxxxxxxxxxx <linux-kernel-owner@xxxxxxxxxxxxxxx> On Behalf
> Of Jia-Ju Bai
> Sent: Sunday, March 18, 2018 7:53 AM
> To: KY Srinivasan <kys@xxxxxxxxxxxxx>; Haiyang Zhang <haiyangz@xxxxxxxxxxxxx>; Stephen
> Hemminger <sthemmin@xxxxxxxxxxxxx>; bhelgaas@xxxxxxxxxx
> Cc: devel@xxxxxxxxxxxxxxxxxxxxxx; linux-pci@xxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx;
> Jia-Ju Bai <baijiaju1990@xxxxxxxxx>
> Subject: [PATCH 2/2] pci: host: pci-hyperv: Replace GFP_ATOMIC with GFP_KERNEL in
> new_pcichild_device
> 
> new_pcichild_device() is not called in atomic context.
> 
> The call chain ending up at new_pcichild_device() is:
> [1] new_pcichild_device() <- pci_devices_present_work()
> pci_devices_present_work() is only set in INIT_WORK().
> 
> Despite never getting called from atomic context,
> new_pcichild_device() calls kzalloc with GFP_ATOMIC,
> which waits busily for allocation.
> GFP_ATOMIC is not necessary and can be replaced with GFP_KERNEL
> to avoid busy waiting.
> 
> This is found by a static analysis tool named DCNS written by myself.
> 
> Signed-off-by: Jia-Ju Bai <baijiaju1990@xxxxxxxxx>

Reviewed-by: Michael Kelley <mikelley@xxxxxxxxxxxxx>

> ---
>  drivers/pci/host/pci-hyperv.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/pci/host/pci-hyperv.c b/drivers/pci/host/pci-hyperv.c
> index 0fe3ea1..289e31d 100644
> --- a/drivers/pci/host/pci-hyperv.c
> +++ b/drivers/pci/host/pci-hyperv.c
> @@ -1500,7 +1500,7 @@ static struct hv_pci_dev *new_pcichild_device(struct
> hv_pcibus_device *hbus,
>  	unsigned long flags;
>  	int ret;
> 
> -	hpdev = kzalloc(sizeof(*hpdev), GFP_ATOMIC);
> +	hpdev = kzalloc(sizeof(*hpdev), GFP_KERNEL);
>  	if (!hpdev)
>  		return NULL;
> 
> --
> 1.9.1