[PATCH] r8152: fix lockup when runtime PM is enabled

[PATCH] r8152: fix lockup when runtime PM is enabled

[Peter Wu]

When an interface is brought up which was previously suspended (via
runtime PM), it would hang. This happens because napi_disable is called
before napi_enable.

Solve this by avoiding napi_disable before the device is fully up.

While at it, remove WORK_ENABLE check from rtl8152_open (introduced with
the original change) because it cannot happen:

 - After this patch, runtime resume will not set it during rtl8152_open.
 - When link is up, rtl8152_open is not called.
 - When link is down during system/auto suspend/resume, it is not set.

Fixes: 41cec84cf285 ("r8152: don't enable napi before rx ready")
Link: https://lkml.kernel.org/r/20151205105912.GA1766@al
Signed-off-by: Peter Wu <peter@lekensteyn.nl>
---
 drivers/net/usb/r8152.c | 23 +++++++----------------
 1 file changed, 7 insertions(+), 16 deletions(-)

diff --git a/drivers/net/usb/r8152.c b/drivers/net/usb/r8152.c
index d9427ca..b8b083e 100644
--- a/drivers/net/usb/r8152.c
+++ b/drivers/net/usb/r8152.c
@@ -3067,17 +3067,6 @@ static int rtl8152_open(struct net_device *netdev)
 
 	mutex_lock(&tp->control);
 
-	/* The WORK_ENABLE may be set when autoresume occurs */
-	if (test_bit(WORK_ENABLE, &tp->flags)) {
-		clear_bit(WORK_ENABLE, &tp->flags);
-		usb_kill_urb(tp->intr_urb);
-		cancel_delayed_work_sync(&tp->schedule);
-
-		/* disable the tx/rx, if the workqueue has enabled them. */
-		if (netif_carrier_ok(netdev))
-			tp->rtl_ops.disable(tp);
-	}
-
 	tp->rtl_ops.up(tp);
 
 	rtl8152_set_speed(tp, AUTONEG_ENABLE,
@@ -3516,11 +3505,13 @@ static int rtl8152_resume(struct usb_interface *intf)
 		if (test_bit(SELECTIVE_SUSPEND, &tp->flags)) {
 			rtl_runtime_suspend_enable(tp, false);
 			clear_bit(SELECTIVE_SUSPEND, &tp->flags);
-			napi_disable(&tp->napi);
-			set_bit(WORK_ENABLE, &tp->flags);
-			if (netif_carrier_ok(tp->netdev))
-				rtl_start_rx(tp);
-			napi_enable(&tp->napi);
+			if (tp->netdev->flags & IFF_UP) {
+				napi_disable(&tp->napi);
+				set_bit(WORK_ENABLE, &tp->flags);
+				if (netif_carrier_ok(tp->netdev))
+					rtl_start_rx(tp);
+				napi_enable(&tp->napi);
+			}
 		} else {
 			tp->rtl_ops.up(tp);
 			rtl8152_set_speed(tp, AUTONEG_ENABLE,
-- 
2.6.3

RE: [PATCH] r8152: fix lockup when runtime PM is enabled

[Hayes Wang]

Peter Wu [mailto:peter@lekensteyn.nl]
> Sent: Tuesday, December 08, 2015 12:59 AM
[...]
> +			if (tp->netdev->flags & IFF_UP) {

Maybe you could just replace the checking of netif_running(tp->netdev) with this.

Excuse me. I have a question. Before the open() is finished, the netif_running() would
be true, but the IFF_UP wouldn't be set. Is it right?

Best Regards,
Hayes

Re: [PATCH] r8152: fix lockup when runtime PM is enabled

[Peter Wu]

On Tue, Dec 08, 2015 at 03:18:59AM +0000, Hayes Wang wrote:
> Peter Wu
> > Sent: Tuesday, December 08, 2015 12:59 AM
> [...]
> > +			if (tp->netdev->flags & IFF_UP) {
> 
> Maybe you could just replace the checking of netif_running(tp->netdev)
> with this.

Simply replacing netif_running by IFF_UP does not work, it hangs during
close when the device is suspended. This patch is correct, but I have a
v2 patch that moves rtl_runtime_suspend_enable from close to suspend.

This is the evaluated scenario (run = netif_running, up = IFF_UP set):

    # suspended before open
    suspend (run=0, up=0)
    open    (run=1)
    resume  (run=1, up=0)   <-- fixed by patch
    (open ends)

    # while up
    suspend (run=1, up=1)
    resume  (run=1, up=1)   <-- no issue, values match
    suspend (run=1, up=1)

    # close while suspended
    close   (run=0, up=1)
    resume  (run=0, up=1)   <-- fixed in patch v2
    (close cont and ends)   <-- rtl_runtime_suspend_enable removed in v2
    suspend (run=0, up=0)

    # while down
    resume  (run=0, up=0)
    suspend (run=0, up=0)

    # open while suspended, open fails
    open    (run=1)
    resume  (run=1, up=0)   <-- fixed by patch
    (open fails)
    suspend (run=0, up=0)

> Excuse me. I have a question. Before the open() is finished, the
> netif_running() would be true, but the IFF_UP wouldn't be set. Is it
> right?

That is right, this happens behind the scenes:

    # open
    netif_running = true
    open()
    if open succeeded
        set IFF_UP
    else
        netif_running = false

    # close
    netif_running = false
    close()
    clear IFF_UP
-- 
Kind regards,
Peter Wu
https://lekensteyn.nl