> -----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 1/2] pci: host: pci-hyperv: Replace GFP_ATOMIC with GFP_KERNEL in > hv_pci_onchannelcallback > > hv_pci_onchannelcallback() is not called in atomic context. > > The call chain ending up at hv_pci_onchannelcallback() is: > [1] hv_pci_onchannelcallback() <- hv_pci_probe() > hv_pci_probe() is only set as ".probe" in hv_driver > structure "hv_pci_drv". > > Despite never getting called from atomic context, Not true. hv_pci_probe() registers hv_pci_onchannelcallback() as a callback function that is invoked from the VMbus interrupt handler. So GFP_ATOMIC is appropriate. Michael > hv_pci_onchannelcallback() calls kmalloc 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> > --- > drivers/pci/host/pci-hyperv.c | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/drivers/pci/host/pci-hyperv.c b/drivers/pci/host/pci-hyperv.c > index 0fe3ea1..c5c8a99 100644 > --- a/drivers/pci/host/pci-hyperv.c > +++ b/drivers/pci/host/pci-hyperv.c > @@ -1887,7 +1887,7 @@ static void hv_pci_onchannelcallback(void *context) > struct pci_dev_incoming *dev_message; > struct hv_pci_dev *hpdev; > > - buffer = kmalloc(bufferlen, GFP_ATOMIC); > + buffer = kmalloc(bufferlen, GFP_KERNEL); > if (!buffer) > return; > > @@ -1899,7 +1899,7 @@ static void hv_pci_onchannelcallback(void *context) > kfree(buffer); > /* Handle large packet */ > bufferlen = bytes_recvd; > - buffer = kmalloc(bytes_recvd, GFP_ATOMIC); > + buffer = kmalloc(bytes_recvd, GFP_KERNEL); > if (!buffer) > return; > continue; > -- > 1.9.1
