Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]

Groups > linux.kernel > #1607630

Re: deadlock in synchronize_srcu() in debugfs?

Show all headers | View raw

Hi Johannes,

On Thu, Mar 23 2017, Johannes Berg wrote:

> Before I go hunting - has anyone seen a deadlock in synchronize_srcu()
> in debugfs_remove() before?

Not yet. How reproducible is this?


> We're observing that with our (backported, but very recent) driver
> against 4.9 (and 4.10, I think),

Do I understand it correctly that this driver has been backported from
4.11-rcX to 4.9/10 and that there isn't any issue with 4.11-rcX?


> but there are no backports of any debugfs things so the backport
> itself doesn't seem like a likely problem.

Right, there haven't been any SRCU related changes to debugfs after
4.8.


> sysrq-w shows a lot of tasks blocked on various locks (e.g. RTNL), but
> the ultimate problem is the wireless stack getting blocked on
> debugfs_remove_recursive(), in __synchronize_srcu(), in
> wait_for_completion() (while holding lots of locks, hence the other
> tasks getting stuck).

Could you share a complete backtrace? For example, is the
debugfs_remove_recursive() called from any debugfs file's fops and thus,
possibly from within a SRCU read side critical section?


Thanks,

Nicolai

Back to linux.kernel | Previous | Next — Previous in thread | Next in thread | Find similar | Unroll thread

Thread

deadlock in synchronize_srcu() in debugfs? Johannes Berg <johannes@sipsolutions.net> - 2017-03-23 16:00 +0100
  Re: deadlock in synchronize_srcu() in debugfs? Nicolai Stange <nicstange@gmail.com> - 2017-03-23 16:40 +0100
    Re: deadlock in synchronize_srcu() in debugfs? Johannes Berg <johannes@sipsolutions.net> - 2017-03-23 16:50 +0100
    Re: deadlock in synchronize_srcu() in debugfs? Johannes Berg <johannes@sipsolutions.net> - 2017-03-27 14:00 +0200
  Re: deadlock in synchronize_srcu() in debugfs? "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2017-03-23 16:40 +0100
    Re: deadlock in synchronize_srcu() in debugfs? Johannes Berg <johannes@sipsolutions.net> - 2017-03-23 16:50 +0100
  Re: deadlock in synchronize_srcu() in debugfs? Johannes Berg <johannes@sipsolutions.net> - 2017-03-23 16:40 +0100
    Re: deadlock in synchronize_srcu() in debugfs? Johannes Berg <johannes@sipsolutions.net> - 2017-03-24 10:00 +0100
      Re: deadlock in synchronize_srcu() in debugfs? Johannes Berg <johannes@sipsolutions.net> - 2017-03-24 10:30 +0100
        Re: deadlock in synchronize_srcu() in debugfs? "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2017-03-24 18:50 +0100
          Re: deadlock in synchronize_srcu() in debugfs? Johannes Berg <johannes@sipsolutions.net> - 2017-03-24 20:00 +0100
            Re: deadlock in synchronize_srcu() in debugfs? "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2017-03-24 20:40 +0100
              Re: deadlock in synchronize_srcu() in debugfs? "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2017-03-24 21:30 +0100
                Re: deadlock in synchronize_srcu() in debugfs? Johannes Berg <johannes@sipsolutions.net> - 2017-03-27 13:20 +0200

csiph-web