On Thu, Jul 18, 2019 at 12:45:47PM +0100, Will Deacon wrote:
> On Thu, Jul 18, 2019 at 12:58:12PM +0200, Peter Zijlstra wrote:
> > On Thu, Jul 18, 2019 at 10:26:41AM +0100, Will Deacon wrote:
> >
> > > /*
> > > * We need to ensure ACQUIRE semantics when reading sem->count so that
> > > * we pair
On Thu, Jul 18, 2019 at 06:50:52AM -0400, Jan Stancek wrote:
>
> - Original Message -
> > Hi Jan, Waiman, [+Jade and Paul for the litmus test at the end]
> >
> > On Wed, Jul 17, 2019 at 09:22:00PM +0200, Jan Stancek wrote:
> > > On Wed, Jul 17, 2019 at 10:19:04AM -0400, Waiman Long wrote:
On Thu, Jul 18, 2019 at 12:58:12PM +0200, Peter Zijlstra wrote:
> On Thu, Jul 18, 2019 at 10:26:41AM +0100, Will Deacon wrote:
>
> > /*
> > * We need to ensure ACQUIRE semantics when reading sem->count so that
> > * we pair with the RELEASE store performed by an unlocking/downgrading
> > * writ
- Original Message -
>
> It's simpler like so:
>
> On Thu, Jul 18, 2019 at 01:04:46PM +0200, Peter Zijlstra wrote:
> > X = 0;
> >
> > rwsem_down_read()
> > for (;;) {
> > set_current_state(TASK_UNINTERRUPTIBLE);
> >
> >
It's simpler like so:
On Thu, Jul 18, 2019 at 01:04:46PM +0200, Peter Zijlstra wrote:
> X = 0;
>
> rwsem_down_read()
> for (;;) {
> set_current_state(TASK_UNINTERRUPTIBLE);
>
> X = 1;
>
On Thu, Jul 18, 2019 at 06:50:52AM -0400, Jan Stancek wrote:
> > In writing this, I also noticed that we don't have any explicit ordering
> > at the end of the reader slowpath when we wait on the queue but get woken
> > immediately:
> >
> > if (!waiter.task)
> > break;
> >
> > Am
On Thu, Jul 18, 2019 at 10:26:41AM +0100, Will Deacon wrote:
> /*
> * We need to ensure ACQUIRE semantics when reading sem->count so that
> * we pair with the RELEASE store performed by an unlocking/downgrading
> * writer.
> *
> * P0 (writer)P1 (reader)
> *
> * down_
- Original Message -
> Hi Jan, Waiman, [+Jade and Paul for the litmus test at the end]
>
> On Wed, Jul 17, 2019 at 09:22:00PM +0200, Jan Stancek wrote:
> > On Wed, Jul 17, 2019 at 10:19:04AM -0400, Waiman Long wrote:
> > > > If you add a comment to the code outlining the issue (preferabl
Hi Jan, Waiman, [+Jade and Paul for the litmus test at the end]
On Wed, Jul 17, 2019 at 09:22:00PM +0200, Jan Stancek wrote:
> On Wed, Jul 17, 2019 at 10:19:04AM -0400, Waiman Long wrote:
> > > If you add a comment to the code outlining the issue (preferably as a
> > > litmus
> > > test involving
On 7/17/19 3:22 PM, Jan Stancek wrote:
> On Wed, Jul 17, 2019 at 10:19:04AM -0400, Waiman Long wrote:
>>> If you add a comment to the code outlining the issue (preferably as
>>> a litmus
>>> test involving sem->count and some shared data which happens to be
>>> vmacache_seqnum in your test)), then:
On Wed, Jul 17, 2019 at 10:19:04AM -0400, Waiman Long wrote:
If you add a comment to the code outlining the issue (preferably as a litmus
test involving sem->count and some shared data which happens to be
vmacache_seqnum in your test)), then:
Reviewed-by: Will Deacon
Thanks,
Will
Agreed. A
On 7/17/19 8:02 AM, Jan Stancek wrote:
> LTP mtest06 has been observed to rarely hit "still mapped when deleted"
> and following BUG_ON on arm64:
> page:7e02fa37e480 refcount:3 mapcount:1 mapping:80be3d678ab0
> index:0x0
> xfs_address_space_operations [xfs]
> flags: 0xbfffe00037(
On 7/17/19 9:13 AM, Will Deacon wrote:
> On Wed, Jul 17, 2019 at 02:02:20PM +0200, Jan Stancek wrote:
>> LTP mtest06 has been observed to rarely hit "still mapped when deleted"
>> and following BUG_ON on arm64:
>> page:7e02fa37e480 refcount:3 mapcount:1 mapping:80be3d678ab0
>> index:0x0
On Wed, Jul 17, 2019 at 02:02:20PM +0200, Jan Stancek wrote:
> LTP mtest06 has been observed to rarely hit "still mapped when deleted"
> and following BUG_ON on arm64:
> page:7e02fa37e480 refcount:3 mapcount:1 mapping:80be3d678ab0
> index:0x0
> xfs_address_space_operations [xfs]
> fl
LTP mtest06 has been observed to rarely hit "still mapped when deleted"
and following BUG_ON on arm64:
page:7e02fa37e480 refcount:3 mapcount:1 mapping:80be3d678ab0 index:0x0
xfs_address_space_operations [xfs]
flags: 0xbfffe00037(locked|referenced|uptodate|lru|active)
page dumped
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