On Wed, Sep 06, 2017 at 04:19:04PM +0200, David Sterba wrote: > On Fri, Sep 01, 2017 at 04:14:27PM -0600, Liu Bo wrote: > > wake_up() will go to check whether someone is on the waiting list with > > holding spin_lock(). > > > > Around some btrfs code, we don't check waitqueue_active() firstly, so > > the spin_lock() pair in wake_up() is called even if no one is waiting > > on the queue. > > > > There are more wake_up()s without waitqueue_active(), but these two > > are the hottest one I've run into so far. > > > > Signed-off-by: Liu Bo <bo.li.liu@xxxxxxxxxx> > > Can you please split the patch and address both separately, as they are > not affecting the same data structure? It would be good to mention the > other parts of code specifically (not just "around some code"), or > briefly describe the state transitions where it matters for the wake > ups. > OK. > A missed wakeup appears as if the system is hung, but it's not a > deadlock and we don't have much help debugging that when it happens. I'd > like to review that in a way where I can make sure you have checked all > the possible lost wakeups. Good point, but it seems that we could only prove it on code level (like the comments put around the code). -liubo -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
