On Thu, Oct 08, 2020 at 10:01:48AM -0400, Alan Stern wrote:
> On Wed, Oct 07, 2020 at 07:50:25PM -0700, Paul E. McKenney wrote:
> > There are some distractions at the moment.
> >
> > Please see below. If this is not exactly correct, I will use "git rm"
> > and let you submit the patch as you
On Wed, Oct 07, 2020 at 07:50:25PM -0700, Paul E. McKenney wrote:
> There are some distractions at the moment.
>
> Please see below. If this is not exactly correct, I will use "git rm"
> and let you submit the patch as you wish.
>
> Thanx, Paul
>
>
On Wed, Oct 07, 2020 at 10:25:37PM -0400, Alan Stern wrote:
> On Wed, Oct 07, 2020 at 03:38:51PM -0700, Paul E. McKenney wrote:
> > On Wed, Oct 07, 2020 at 03:40:50PM -0400, Alan Stern wrote:
> > > On Wed, Oct 07, 2020 at 10:50:40AM -0700, Paul E. McKenney wrote:
> > > > And here is the updated
On Wed, Oct 07, 2020 at 03:38:51PM -0700, Paul E. McKenney wrote:
> On Wed, Oct 07, 2020 at 03:40:50PM -0400, Alan Stern wrote:
> > On Wed, Oct 07, 2020 at 10:50:40AM -0700, Paul E. McKenney wrote:
> > > And here is the updated version.
> > >
> > >
On Wed, Oct 07, 2020 at 03:40:50PM -0400, Alan Stern wrote:
> On Wed, Oct 07, 2020 at 10:50:40AM -0700, Paul E. McKenney wrote:
> > And here is the updated version.
> >
> > Thanx, Paul
> >
> >
On Wed, Oct 07, 2020 at 10:50:40AM -0700, Paul E. McKenney wrote:
> And here is the updated version.
>
> Thanx, Paul
>
>
>
> commit
On Tue, Oct 06, 2020 at 01:05:25PM -0400, Alan Stern wrote:
> On Tue, Oct 06, 2020 at 09:39:54AM -0700, Paul E. McKenney wrote:
> > On Mon, Oct 05, 2020 at 03:48:34PM -0400, Alan Stern wrote:
> > > On Mon, Oct 05, 2020 at 12:18:01PM -0700, Paul E. McKenney wrote:
> > > > Aside from naming and
On Tue, Oct 06, 2020 at 09:39:54AM -0700, Paul E. McKenney wrote:
> On Mon, Oct 05, 2020 at 03:48:34PM -0400, Alan Stern wrote:
> > On Mon, Oct 05, 2020 at 12:18:01PM -0700, Paul E. McKenney wrote:
> > > Aside from naming and comment, how about my adding the following?
> > >
> > >
On Mon, Oct 05, 2020 at 03:48:34PM -0400, Alan Stern wrote:
> On Mon, Oct 05, 2020 at 12:18:01PM -0700, Paul E. McKenney wrote:
> > Aside from naming and comment, how about my adding the following?
> >
> > Thanx, Paul
> >
> >
On Mon, Oct 05, 2020 at 12:18:01PM -0700, Paul E. McKenney wrote:
> Aside from naming and comment, how about my adding the following?
>
> Thanx, Paul
>
>
>
> C
On Mon, Oct 05, 2020 at 02:19:49PM -0400, Alan Stern wrote:
> On Mon, Oct 05, 2020 at 09:52:23AM -0700, Paul E. McKenney wrote:
> > On Mon, Oct 05, 2020 at 11:53:10AM -0400, Alan Stern wrote:
> > > I tested the new commit -- it does indeed fix the problem.
> >
> > Beat me to it, very good! ;-)
>
On Mon, Oct 05, 2020 at 09:52:23AM -0700, Paul E. McKenney wrote:
> On Mon, Oct 05, 2020 at 11:53:10AM -0400, Alan Stern wrote:
> > I tested the new commit -- it does indeed fix the problem.
>
> Beat me to it, very good! ;-)
>
> But were you using the crypto-control-data litmus test?
I was
On Mon, Oct 05, 2020 at 11:53:10AM -0400, Alan Stern wrote:
> On Mon, Oct 05, 2020 at 05:15:57PM +0200, Luc Maranget wrote:
> > > On Sun, Oct 04, 2020 at 12:16:31AM +0900, Akira Yokosawa wrote:
> > > > > P1(int *x, int *y)
> > > > > {
> > > > > WRITE_ONCE(*x, READ_ONCE(*y));
> > > >
> > > >
On Mon, Oct 05, 2020 at 10:44:22AM -0400, j...@joelfernandes.org wrote:
> On Mon, Oct 05, 2020 at 07:03:53AM -0700, Paul E. McKenney wrote:
> > On Sun, Oct 04, 2020 at 10:38:46PM -0400, Alan Stern wrote:
> > > On Sun, Oct 04, 2020 at 04:31:46PM -0700, Paul E. McKenney wrote:
> > > > Nice simple
On Mon, Oct 05, 2020 at 05:15:57PM +0200, Luc Maranget wrote:
> > On Sun, Oct 04, 2020 at 12:16:31AM +0900, Akira Yokosawa wrote:
> > > Hi Alan,
> > >
> > > Just a minor nit in the litmus test.
> > >
> > > On Sat, 3 Oct 2020 09:22:12 -0400, Alan Stern wrote:
> > > > To expand on my statement
On Mon, Oct 05, 2020 at 05:15:57PM +0200, Luc Maranget wrote:
> > On Sun, Oct 04, 2020 at 12:16:31AM +0900, Akira Yokosawa wrote:
> > > > P1(int *x, int *y)
> > > > {
> > > > WRITE_ONCE(*x, READ_ONCE(*y));
> > >
> > > Looks like this one-liner doesn't provide data-dependency of y -> x on
On Mon, Oct 05, 2020 at 05:35:19PM +0200, Peter Zijlstra wrote:
> On Mon, Oct 05, 2020 at 11:16:39AM -0400, Alan Stern wrote:
> > On Mon, Oct 05, 2020 at 04:13:13PM +0100, Will Deacon wrote:
> > > > The failure to recognize the dependency in P0 should be considered a
> > > > combined limitation
On Mon, Oct 05, 2020 at 11:16:39AM -0400, Alan Stern wrote:
> On Mon, Oct 05, 2020 at 04:13:13PM +0100, Will Deacon wrote:
> > > The failure to recognize the dependency in P0 should be considered a
> > > combined limitation of the memory model and herd7. It's not a simple
> > > mistake that can
On Mon, Oct 05, 2020 at 04:13:13PM +0100, Will Deacon wrote:
> > The failure to recognize the dependency in P0 should be considered a
> > combined limitation of the memory model and herd7. It's not a simple
> > mistake that can be fixed by a small rewrite of herd7; rather it's a
> > deliberate
> On Sun, Oct 04, 2020 at 12:16:31AM +0900, Akira Yokosawa wrote:
> > Hi Alan,
> >
> > Just a minor nit in the litmus test.
> >
> > On Sat, 3 Oct 2020 09:22:12 -0400, Alan Stern wrote:
> > > To expand on my statement about the LKMM's weakness regarding control
> > > constructs, here is a litmus
On Mon, Oct 05, 2020 at 10:23:51AM -0400, Alan Stern wrote:
> On Mon, Oct 05, 2020 at 10:12:48AM +0100, Will Deacon wrote:
> > On Mon, Oct 05, 2020 at 09:20:03AM +0100, Will Deacon wrote:
> > > On Sun, Oct 04, 2020 at 10:38:46PM -0400, Alan Stern wrote:
> > > > Considering the bug in herd7 pointed
On Mon, Oct 05, 2020 at 07:03:53AM -0700, Paul E. McKenney wrote:
> On Sun, Oct 04, 2020 at 10:38:46PM -0400, Alan Stern wrote:
> > On Sun, Oct 04, 2020 at 04:31:46PM -0700, Paul E. McKenney wrote:
> > > Nice simple example! How about like this?
> > >
> > >
On Mon, Oct 05, 2020 at 07:03:53AM -0700, Paul E. McKenney wrote:
> Updated as suggested by Will, like this?
>
> Thanx, Paul
>
>
>
> commit
On Mon, Oct 05, 2020 at 10:12:48AM +0100, Will Deacon wrote:
> On Mon, Oct 05, 2020 at 09:20:03AM +0100, Will Deacon wrote:
> > On Sun, Oct 04, 2020 at 10:38:46PM -0400, Alan Stern wrote:
> > > Considering the bug in herd7 pointed out by Akira, we should rewrite P1
> > > as:
> > >
> > > P1(int
On Mon, Oct 05, 2020 at 09:20:03AM +0100, Will Deacon wrote:
> On Sun, Oct 04, 2020 at 10:38:46PM -0400, Alan Stern wrote:
> > Considering the bug in herd7 pointed out by Akira, we should rewrite P1 as:
> >
> > P1(int *x, int *y)
> > {
> > int r2;
> >
> > r = READ_ONCE(*y);
>
> (r2?)
On Sun, Oct 04, 2020 at 10:38:46PM -0400, Alan Stern wrote:
> On Sun, Oct 04, 2020 at 04:31:46PM -0700, Paul E. McKenney wrote:
> > Nice simple example! How about like this?
> >
> > Thanx, Paul
> >
> >
On Mon, Oct 05, 2020 at 10:12:48AM +0100, Will Deacon wrote:
> On Mon, Oct 05, 2020 at 09:20:03AM +0100, Will Deacon wrote:
> > On Sun, Oct 04, 2020 at 10:38:46PM -0400, Alan Stern wrote:
> > > On Sun, Oct 04, 2020 at 04:31:46PM -0700, Paul E. McKenney wrote:
> > > > Nice simple example! How
On Mon, Oct 05, 2020 at 08:36:51AM +, David Laight wrote:
> From: Paul E. McKenney
> > Sent: 05 October 2020 00:32
> ...
> > manual/kernel: Add a litmus test with a hidden dependency
> >
> > This commit adds a litmus test that has a data dependency that can be
> > hidden by
On Mon, Oct 05, 2020 at 09:20:03AM +0100, Will Deacon wrote:
> On Sun, Oct 04, 2020 at 10:38:46PM -0400, Alan Stern wrote:
> > On Sun, Oct 04, 2020 at 04:31:46PM -0700, Paul E. McKenney wrote:
> > > Nice simple example! How about like this?
> > >
> > >
From: Paul E. McKenney
> Sent: 05 October 2020 00:32
...
> manual/kernel: Add a litmus test with a hidden dependency
>
> This commit adds a litmus test that has a data dependency that can be
> hidden by control flow. In this test, both the taken and the not-taken
> branches of an
On Sun, Oct 04, 2020 at 10:38:46PM -0400, Alan Stern wrote:
> On Sun, Oct 04, 2020 at 04:31:46PM -0700, Paul E. McKenney wrote:
> > Nice simple example! How about like this?
> >
> > Thanx, Paul
> >
> >
On Sun, Oct 04, 2020 at 04:31:46PM -0700, Paul E. McKenney wrote:
> Nice simple example! How about like this?
>
> Thanx, Paul
>
>
>
> commit
On Fri, Oct 02, 2020 at 10:35:45PM -0400, Jon Masters wrote:
> On 10/1/20 12:15 PM, Alan Stern wrote:
> > On Wed, Sep 30, 2020 at 09:51:16PM -0700, Paul E. McKenney wrote:
> > > Hello!
> > >
> > > Al Viro posted the following query:
> > >
> > >
On Sat, Oct 03, 2020 at 09:22:12AM -0400, Alan Stern wrote:
> To expand on my statement about the LKMM's weakness regarding control
> constructs, here is a litmus test to illustrate the issue. You might
> want to add this to one of the archives.
>
> Alan
>
> C crypto-control-data
> (*
> * LB
On Sat, Oct 03, 2020 at 12:11:59PM -0400, j...@joelfernandes.org wrote:
> On Sat, Oct 03, 2020 at 12:08:46PM -0400, j...@joelfernandes.org wrote:
> [...]
> > static void code0(struct v_struct* v,spinlock_t* l,int* out_0_r1) {
> >
> > struct v_struct *r1; /* to_free */
> >
> > r1
On Sat, 3 Oct 2020 13:13:38 -0400, Alan Stern wrote:
> On Sun, Oct 04, 2020 at 12:16:31AM +0900, Akira Yokosawa wrote:
>> Hi Alan,
>>
>> Just a minor nit in the litmus test.
>>
>> On Sat, 3 Oct 2020 09:22:12 -0400, Alan Stern wrote:
>>> To expand on my statement about the LKMM's weakness regarding
On Sun, Oct 04, 2020 at 12:16:31AM +0900, Akira Yokosawa wrote:
> Hi Alan,
>
> Just a minor nit in the litmus test.
>
> On Sat, 3 Oct 2020 09:22:12 -0400, Alan Stern wrote:
> > To expand on my statement about the LKMM's weakness regarding control
> > constructs, here is a litmus test to
On Sat, Oct 03, 2020 at 12:08:46PM -0400, j...@joelfernandes.org wrote:
[...]
> static void code0(struct v_struct* v,spinlock_t* l,int* out_0_r1) {
>
> struct v_struct *r1; /* to_free */
>
> r1 = NULL;
> spin_lock(l);
> if (!smp_load_acquire(>b))
>
On Thu, Oct 01, 2020 at 02:30:48PM -0700, Paul E. McKenney wrote:
> On Thu, Oct 01, 2020 at 12:15:29PM -0400, Alan Stern wrote:
> > On Wed, Sep 30, 2020 at 09:51:16PM -0700, Paul E. McKenney wrote:
> > > Hello!
> > >
> > > Al Viro posted the following query:
> > >
> > >
Hi Alan,
Just a minor nit in the litmus test.
On Sat, 3 Oct 2020 09:22:12 -0400, Alan Stern wrote:
> To expand on my statement about the LKMM's weakness regarding control
> constructs, here is a litmus test to illustrate the issue. You might
> want to add this to one of the archives.
>
>
To expand on my statement about the LKMM's weakness regarding control
constructs, here is a litmus test to illustrate the issue. You might
want to add this to one of the archives.
Alan
C crypto-control-data
(*
* LB plus crypto-control-data plus data
*
* Expected result: allowed
*
* This
On 10/1/20 12:15 PM, Alan Stern wrote:
On Wed, Sep 30, 2020 at 09:51:16PM -0700, Paul E. McKenney wrote:
Hello!
Al Viro posted the following query:
fun question regarding barriers, if you have time for that
On Thu, Oct 01, 2020 at 02:30:48PM -0700, Paul E. McKenney wrote:
> > Not the way I would have done it, but okay. I would have modeled the
> > kfree by setting a and b both to some sentinel value.
>
> Might be well worth pursuing! But how would you model the address
> dependencies in that
On Thu, Oct 01, 2020 at 12:15:29PM -0400, Alan Stern wrote:
> On Wed, Sep 30, 2020 at 09:51:16PM -0700, Paul E. McKenney wrote:
> > Hello!
> >
> > Al Viro posted the following query:
> >
> >
> >
> > fun question regarding
On Thu, Oct 01, 2020 at 02:39:25PM -0400, Alan Stern wrote:
> The problem with a plain write is that it isn't guaranteed to be atomic
> in any sense. In principle, the compiler could generate code for CPU1
> which would write 0 to V->A more than once.
>
> Although I strongly doubt that any
On Thu, Oct 01, 2020 at 05:36:46PM +0100, Al Viro wrote:
> On Thu, Oct 01, 2020 at 12:15:29PM -0400, Alan Stern wrote:
> > > CPU1:
> > > to_free = NULL
> > > spin_lock()
> > > if (!smp_load_acquire(>B))
> > > to_free = V
> > > V->A = 0
> > >
On Thu, Oct 01, 2020 at 12:15:29PM -0400, Alan Stern wrote:
> > CPU1:
> > to_free = NULL
> > spin_lock()
> > if (!smp_load_acquire(>B))
> > to_free = V
> > V->A = 0
> > spin_unlock()
> > kfree(to_free)
> >
> > CPU2:
> >
On Wed, Sep 30, 2020 at 09:51:16PM -0700, Paul E. McKenney wrote:
> Hello!
>
> Al Viro posted the following query:
>
>
>
> fun question regarding barriers, if you have time for that
> V->A = V->B = 1;
>
> CPU1:
Hello!
Al Viro posted the following query:
fun question regarding barriers, if you have time for that
V->A = V->B = 1;
CPU1:
to_free = NULL
spin_lock()
if (!smp_load_acquire(>B))
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