From: "Michael S. Tsirkin" <mst@redhat.com>
To: Joel Fernandes <joel@joelfernandes.org>
Cc: "Paul E. McKenney" <paulmck@linux.ibm.com>,
Matthew Wilcox <willy@infradead.org>,
aarcange@redhat.com, akpm@linux-foundation.org,
christian@brauner.io, davem@davemloft.net, ebiederm@xmission.com,
elena.reshetova@intel.com, guro@fb.com, hch@infradead.org,
james.bottomley@hansenpartnership.com, jasowang@redhat.com,
jglisse@redhat.com, keescook@chromium.org, ldv@altlinux.org,
linux-arm-kernel@lists.infradead.org,
linux-kernel@vger.kernel.org, linux-mm@kvack.org,
linux-parisc@vger.kernel.org, luto@amacapital.net,
mhocko@suse.com, mingo@kernel.org, namit@vmware.com,
peterz@infradead.org, syzkaller-bugs@googlegroups.com,
viro@zeniv.linux.org.uk, wad@chromium.org
Subject: Re: RFC: call_rcu_outstanding (was Re: WARNING in __mmdrop)
Date: Mon, 22 Jul 2019 11:47:24 -0400 [thread overview]
Message-ID: <20190722114612-mutt-send-email-mst@kernel.org> (raw)
In-Reply-To: <20190722151439.GA247639@google.com>
On Mon, Jul 22, 2019 at 11:14:39AM -0400, Joel Fernandes wrote:
> [snip]
> > > Would it make sense to have call_rcu() check to see if there are many
> > > outstanding requests on this CPU and if so process them before returning?
> > > That would ensure that frequent callers usually ended up doing their
> > > own processing.
>
> Other than what Paul already mentioned about deadlocks, I am not sure if this
> would even work for all cases since call_rcu() has to wait for a grace
> period.
>
> So, if the number of outstanding requests are higher than a certain amount,
> then you *still* have to wait for some RCU configurations for the grace
> period duration and cannot just execute the callback in-line. Did I miss
> something?
>
> Can waiting in-line for a grace period duration be tolerated in the vhost case?
>
> thanks,
>
> - Joel
No, but it has many other ways to recover (try again later, drop a
packet, use a slower copy to/from user).
--
MST
next prev parent reply other threads:[~2019-07-22 15:47 UTC|newest]
Thread overview: 87+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <0000000000008dd6bb058e006938@google.com>
2019-07-20 10:08 ` WARNING in __mmdrop syzbot
2019-07-21 10:02 ` Michael S. Tsirkin
2019-07-21 12:18 ` Michael S. Tsirkin
2019-07-22 5:24 ` Jason Wang
2019-07-22 8:08 ` Michael S. Tsirkin
2019-07-23 4:01 ` Jason Wang
2019-07-23 5:01 ` Michael S. Tsirkin
2019-07-23 5:47 ` Jason Wang
2019-07-23 7:23 ` Michael S. Tsirkin
2019-07-23 7:53 ` Jason Wang
2019-07-23 8:10 ` Michael S. Tsirkin
2019-07-23 8:49 ` Jason Wang
2019-07-23 9:26 ` Michael S. Tsirkin
2019-07-23 13:31 ` Jason Wang
2019-07-25 5:52 ` Michael S. Tsirkin
2019-07-25 7:43 ` Jason Wang
2019-07-25 8:28 ` Michael S. Tsirkin
2019-07-25 13:21 ` Jason Wang
2019-07-25 13:26 ` Michael S. Tsirkin
2019-07-25 14:25 ` Jason Wang
2019-07-26 11:49 ` Michael S. Tsirkin
2019-07-26 12:00 ` Jason Wang
2019-07-26 12:38 ` Michael S. Tsirkin
2019-07-26 12:53 ` Jason Wang
2019-07-26 13:36 ` Jason Wang
2019-07-26 13:49 ` Michael S. Tsirkin
2019-07-29 5:54 ` Jason Wang
2019-07-29 8:59 ` Michael S. Tsirkin
2019-07-29 14:24 ` Jason Wang
2019-07-29 14:44 ` Michael S. Tsirkin
2019-07-30 7:44 ` Jason Wang
2019-07-30 8:03 ` Jason Wang
2019-07-30 15:08 ` Michael S. Tsirkin
2019-07-31 8:49 ` Jason Wang
2019-07-31 23:00 ` Jason Gunthorpe
2019-07-26 13:47 ` Michael S. Tsirkin
2019-07-26 14:00 ` Jason Wang
2019-07-26 14:10 ` Michael S. Tsirkin
2019-07-26 15:03 ` Jason Gunthorpe
2019-07-29 5:56 ` Jason Wang
2019-07-21 12:28 ` RFC: call_rcu_outstanding (was Re: WARNING in __mmdrop) Michael S. Tsirkin
2019-07-21 13:17 ` Paul E. McKenney
2019-07-21 17:53 ` Michael S. Tsirkin
2019-07-21 19:28 ` Paul E. McKenney
2019-07-22 7:56 ` Michael S. Tsirkin
2019-07-22 11:57 ` Paul E. McKenney
2019-07-21 21:08 ` Matthew Wilcox
2019-07-21 23:31 ` Paul E. McKenney
2019-07-22 7:52 ` Michael S. Tsirkin
2019-07-22 11:51 ` Paul E. McKenney
2019-07-22 13:41 ` Jason Gunthorpe
2019-07-22 15:52 ` Paul E. McKenney
2019-07-22 16:04 ` Jason Gunthorpe
2019-07-22 16:15 ` Michael S. Tsirkin
2019-07-22 16:15 ` Paul E. McKenney
2019-07-22 15:14 ` Joel Fernandes
2019-07-22 15:47 ` Michael S. Tsirkin [this message]
2019-07-22 15:55 ` Paul E. McKenney
2019-07-22 16:13 ` Michael S. Tsirkin
2019-07-22 16:25 ` Paul E. McKenney
2019-07-22 16:32 ` Michael S. Tsirkin
2019-07-22 18:58 ` Paul E. McKenney
2019-07-22 5:21 ` WARNING in __mmdrop Jason Wang
2019-07-22 8:02 ` Michael S. Tsirkin
2019-07-23 3:55 ` Jason Wang
2019-07-23 5:02 ` Michael S. Tsirkin
2019-07-23 5:48 ` Jason Wang
2019-07-23 7:25 ` Michael S. Tsirkin
2019-07-23 7:55 ` Jason Wang
2019-07-23 7:56 ` Michael S. Tsirkin
2019-07-23 8:42 ` Jason Wang
2019-07-23 10:27 ` Michael S. Tsirkin
2019-07-23 13:34 ` Jason Wang
2019-07-23 15:02 ` Michael S. Tsirkin
2019-07-24 2:17 ` Jason Wang
2019-07-24 8:05 ` Michael S. Tsirkin
2019-07-24 10:08 ` Jason Wang
2019-07-24 18:25 ` Michael S. Tsirkin
2019-07-25 3:44 ` Jason Wang
2019-07-25 5:09 ` Michael S. Tsirkin
2019-07-24 16:53 ` Jason Gunthorpe
2019-07-24 18:25 ` Michael S. Tsirkin
2019-07-23 10:42 ` Michael S. Tsirkin
2019-07-23 13:37 ` Jason Wang
2019-07-22 14:11 ` Jason Gunthorpe
2019-07-25 6:02 ` Michael S. Tsirkin
2019-07-25 7:44 ` Jason Wang
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