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| Started by | David Miller <davem@davemloft.net> |
|---|---|
| First post | 2016-11-26 02:00 +0100 |
| Last post | 2016-12-05 04:30 +0100 |
| Articles | 5 — 3 participants |
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Re: [PATCH RFC] hlist_add_tail_rcu disable sparse warning David Miller <davem@davemloft.net> - 2016-11-26 02:00 +0100
Re: [PATCH RFC] hlist_add_tail_rcu disable sparse warning "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2016-11-28 15:40 +0100
Re: [PATCH RFC] hlist_add_tail_rcu disable sparse warning "Michael S. Tsirkin" <mst@redhat.com> - 2016-11-28 16:40 +0100
Re: [PATCH RFC] hlist_add_tail_rcu disable sparse warning "Michael S. Tsirkin" <mst@redhat.com> - 2016-12-05 04:50 +0100
Re: [PATCH RFC] hlist_add_tail_rcu disable sparse warning "Michael S. Tsirkin" <mst@redhat.com> - 2016-12-05 04:30 +0100
| From | David Miller <davem@davemloft.net> |
|---|---|
| Date | 2016-11-26 02:00 +0100 |
| Subject | Re: [PATCH RFC] hlist_add_tail_rcu disable sparse warning |
| Message-ID | <sHzvr-7Sd-5@gated-at.bofh.it> |
From: "Michael S. Tsirkin" <mst@redhat.com> Date: Wed, 23 Nov 2016 22:48:19 +0200 > I would appreciate review to confirm the function doesn't > do anything unsafe though. > > In particular, should this use __hlist_for_each_rcu instead? > I note that __hlist_for_each_rcu does rcu_dereference > internally, which is missing here. I personally think it should use __hlist_for_each_rcu, otherwise nothing expresses the rcu-ness of the operation.
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| From | "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> |
|---|---|
| Date | 2016-11-28 15:40 +0100 |
| Message-ID | <sIvg5-3iM-17@gated-at.bofh.it> |
| In reply to | #1530576 |
On Fri, Nov 25, 2016 at 07:52:23PM -0500, David Miller wrote: > From: "Michael S. Tsirkin" <mst@redhat.com> > Date: Wed, 23 Nov 2016 22:48:19 +0200 > > > I would appreciate review to confirm the function doesn't > > do anything unsafe though. > > > > In particular, should this use __hlist_for_each_rcu instead? > > I note that __hlist_for_each_rcu does rcu_dereference > > internally, which is missing here. > > I personally think it should use __hlist_for_each_rcu, otherwise > nothing expresses the rcu-ness of the operation. I like Dave's suggestion. Michael, does that change work for you? Thanx, Paul
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| From | "Michael S. Tsirkin" <mst@redhat.com> |
|---|---|
| Date | 2016-11-28 16:40 +0100 |
| Message-ID | <sIwca-3Rx-21@gated-at.bofh.it> |
| In reply to | #1531357 |
On Mon, Nov 28, 2016 at 06:39:19AM -0800, Paul E. McKenney wrote: > On Fri, Nov 25, 2016 at 07:52:23PM -0500, David Miller wrote: > > From: "Michael S. Tsirkin" <mst@redhat.com> > > Date: Wed, 23 Nov 2016 22:48:19 +0200 > > > > > I would appreciate review to confirm the function doesn't > > > do anything unsafe though. > > > > > > In particular, should this use __hlist_for_each_rcu instead? > > > I note that __hlist_for_each_rcu does rcu_dereference > > > internally, which is missing here. > > > > I personally think it should use __hlist_for_each_rcu, otherwise > > nothing expresses the rcu-ness of the operation. > > I like Dave's suggestion. Michael, does that change work for you? > > Thanx, Paul I think it does, I'll try and post the patch. -- MST
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| From | "Michael S. Tsirkin" <mst@redhat.com> |
|---|---|
| Date | 2016-12-05 04:50 +0100 |
| Message-ID | <sKSrU-7zW-11@gated-at.bofh.it> |
| In reply to | #1531357 |
On Mon, Nov 28, 2016 at 06:39:19AM -0800, Paul E. McKenney wrote: > On Fri, Nov 25, 2016 at 07:52:23PM -0500, David Miller wrote: > > From: "Michael S. Tsirkin" <mst@redhat.com> > > Date: Wed, 23 Nov 2016 22:48:19 +0200 > > > > > I would appreciate review to confirm the function doesn't > > > do anything unsafe though. > > > > > > In particular, should this use __hlist_for_each_rcu instead? > > > I note that __hlist_for_each_rcu does rcu_dereference > > > internally, which is missing here. > > > > I personally think it should use __hlist_for_each_rcu, otherwise > > nothing expresses the rcu-ness of the operation. > > I like Dave's suggestion. Michael, does that change work for you? > > Thanx, Paul I think we should change __hlist_for_each_rcu to skip rcu_dereference though then, since it would be called outside any rcu read size critical sections here. -- MST
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| From | "Michael S. Tsirkin" <mst@redhat.com> |
|---|---|
| Date | 2016-12-05 04:30 +0100 |
| Message-ID | <sKS8x-7tO-5@gated-at.bofh.it> |
| In reply to | #1530576 |
On Fri, Nov 25, 2016 at 07:52:23PM -0500, David Miller wrote: > From: "Michael S. Tsirkin" <mst@redhat.com> > Date: Wed, 23 Nov 2016 22:48:19 +0200 > > > I would appreciate review to confirm the function doesn't > > do anything unsafe though. > > > > In particular, should this use __hlist_for_each_rcu instead? > > I note that __hlist_for_each_rcu does rcu_dereference > > internally, which is missing here. > > I personally think it should use __hlist_for_each_rcu, otherwise > nothing expresses the rcu-ness of the operation. What does "rcu-ness" mean in this context? The question is not just about making the code pretty. This operation is called outside any rcu critical section. If you are going to call __hlist_for_each_rcu which calls rcu_dereference, you should do it inside a critical section. Other operations such as hlist_add_behind_rcu manipulate lists manually, maybe this one should, too? Paul? -- MST
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