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 <ta...@ab.jp.nec.com>
---
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
--
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