On 10/09/2015 02:35 AM, Kosuke Tatsukawa wrote: > brcmf_msgbuf_ioctl_resp_wake() seems to be missing a memory barrier > which might cause the waker to not notice the waiter and miss sending a > wake_up as in the following figure. My mail reader treats this as HTML format or so. Can you resend it in plain text please? Regards, Arend > > brcmf_msgbuf_ioctl_resp_wake brcmf_msgbuf_ioctl_resp_wait > ------------------------------------------------------------------------ > if (waitqueue_active(&msgbuf->ioctl_resp_wait)) > /* The CPU might reorder the test for > the waitqueue up here, before > prior writes complete */ > /* wait_event_timeout */ > /* __wait_event_timeout */ > /* ___wait_event */ > prepare_to_wait_event(&wq, &__wait, > state); > if (msgbuf->ctl_completed) > ... > msgbuf->ctl_completed = true; > schedule_timeout(__ret)) > ------------------------------------------------------------------------ > > There are three other place in drivers/net/wireless/brcm80211/brcmfmac/ > which have similar code. The attached patch removes the call to > waitqueue_active() leaving just wake_up() behind. This fixes the > problem because the call to spin_lock_irqsave() in wake_up() will be an > ACQUIRE operation. > > I found this issue when I was looking through the linux source code > for places calling waitqueue_active() before wake_up*(), but without > preceding memory barriers, after sending a patch to fix a similar > issue in drivers/tty/n_tty.c (Details about the original issue can be > found here: https://lkml.org/lkml/2015/9/28/849). > > Signed-off-by: Kosuke Tatsukawa <tatsu@xxxxxxxxxxxxx> > --- > drivers/net/wireless/brcm80211/brcmfmac/msgbuf.c | 3 +-- > drivers/net/wireless/brcm80211/brcmfmac/sdio.c | 6 ++---- > drivers/net/wireless/brcm80211/brcmfmac/usb.c | 3 +-- > 3 files changed, 4 insertions(+), 8 deletions(-) > > diff --git a/drivers/net/wireless/brcm80211/brcmfmac/msgbuf.c b/drivers/net/wireless/brcm80211/brcmfmac/msgbuf.c > index 7b2136c..648151e 100644 > --- a/drivers/net/wireless/brcm80211/brcmfmac/msgbuf.c > +++ b/drivers/net/wireless/brcm80211/brcmfmac/msgbuf.c > @@ -473,8 +473,7 @@ static int brcmf_msgbuf_ioctl_resp_wait(struct brcmf_msgbuf *msgbuf) > static void brcmf_msgbuf_ioctl_resp_wake(struct brcmf_msgbuf *msgbuf) > { > msgbuf->ctl_completed = true; > - if (waitqueue_active(&msgbuf->ioctl_resp_wait)) > - wake_up(&msgbuf->ioctl_resp_wait); > + wake_up(&msgbuf->ioctl_resp_wait); > } > > > diff --git a/drivers/net/wireless/brcm80211/brcmfmac/sdio.c b/drivers/net/wireless/brcm80211/brcmfmac/sdio.c > index f990e3d..332c4c8 100644 > --- a/drivers/net/wireless/brcm80211/brcmfmac/sdio.c > +++ b/drivers/net/wireless/brcm80211/brcmfmac/sdio.c > @@ -1785,8 +1785,7 @@ static int brcmf_sdio_dcmd_resp_wait(struct brcmf_sdio *bus, uint *condition, > > static int brcmf_sdio_dcmd_resp_wake(struct brcmf_sdio *bus) > { > - if (waitqueue_active(&bus->dcmd_resp_wait)) > - wake_up_interruptible(&bus->dcmd_resp_wait); > + wake_up_interruptible(&bus->dcmd_resp_wait); > > return 0; > } > @@ -2110,8 +2109,7 @@ static uint brcmf_sdio_readframes(struct brcmf_sdio *bus, uint maxframes) > static void > brcmf_sdio_wait_event_wakeup(struct brcmf_sdio *bus) > { > - if (waitqueue_active(&bus->ctrl_wait)) > - wake_up_interruptible(&bus->ctrl_wait); > + wake_up_interruptible(&bus->ctrl_wait); > return; > } > > diff --git a/drivers/net/wireless/brcm80211/brcmfmac/usb.c b/drivers/net/wireless/brcm80211/brcmfmac/usb.c > index daba86d..7f5889c 100644 > --- a/drivers/net/wireless/brcm80211/brcmfmac/usb.c > +++ b/drivers/net/wireless/brcm80211/brcmfmac/usb.c > @@ -184,8 +184,7 @@ static int brcmf_usb_ioctl_resp_wait(struct brcmf_usbdev_info *devinfo) > > static void brcmf_usb_ioctl_resp_wake(struct brcmf_usbdev_info *devinfo) > { > - if (waitqueue_active(&devinfo->ioctl_resp_wait)) > - wake_up(&devinfo->ioctl_resp_wait); > + wake_up(&devinfo->ioctl_resp_wait); > } > > static void > -- To unsubscribe from this list: send the line "unsubscribe linux-wireless" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
