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.
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 <[email protected]>
---
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
--
1.7.1
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.
>
> 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).
I prefer to add proper barriers instead of removing waitqueue_active()
check. We will review your patch and submit it through our upstream process.
Regards,
Arend
> Signed-off-by: Kosuke Tatsukawa <[email protected]>
> ---
> 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
>
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 <[email protected]>
> ---
> 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
>