- On Jul 21, 2020, at 11:19 AM, Peter Zijlstra pet...@infradead.org wrote:
> On Tue, Jul 21, 2020 at 11:15:13AM -0400, Mathieu Desnoyers wrote:
>> - On Jul 21, 2020, at 11:06 AM, Peter Zijlstra pet...@infradead.org
>> wrote:
>>
>> > On Tue, Jul 21, 2020 at 08:04:27PM +1000, Nicholas
On Tue, Jul 21, 2020 at 11:15:13AM -0400, Mathieu Desnoyers wrote:
> - On Jul 21, 2020, at 11:06 AM, Peter Zijlstra pet...@infradead.org wrote:
>
> > On Tue, Jul 21, 2020 at 08:04:27PM +1000, Nicholas Piggin wrote:
> >
> >> That being said, the x86 sync core gap that I imagined could be
- On Jul 21, 2020, at 11:06 AM, Peter Zijlstra pet...@infradead.org wrote:
> On Tue, Jul 21, 2020 at 08:04:27PM +1000, Nicholas Piggin wrote:
>
>> That being said, the x86 sync core gap that I imagined could be fixed
>> by changing to rq->curr == rq->idle test does not actually exist because
On Tue, Jul 21, 2020 at 08:04:27PM +1000, Nicholas Piggin wrote:
> That being said, the x86 sync core gap that I imagined could be fixed
> by changing to rq->curr == rq->idle test does not actually exist because
> the global membarrier does not have a sync core option. So fixing the
>
Excerpts from Mathieu Desnoyers's message of July 21, 2020 11:11 pm:
> - On Jul 21, 2020, at 6:04 AM, Nicholas Piggin npig...@gmail.com wrote:
>
>> Excerpts from Mathieu Desnoyers's message of July 21, 2020 2:46 am:
> [...]
>>
>> Yeah you're probably right in this case I think. Quite likely
- On Jul 21, 2020, at 6:04 AM, Nicholas Piggin npig...@gmail.com wrote:
> Excerpts from Mathieu Desnoyers's message of July 21, 2020 2:46 am:
[...]
>
> Yeah you're probably right in this case I think. Quite likely most kernel
> tasks that asynchronously write to user memory would at least
Excerpts from Mathieu Desnoyers's message of July 21, 2020 2:46 am:
> - On Jul 19, 2020, at 11:03 PM, Nicholas Piggin npig...@gmail.com wrote:
>
>> Excerpts from Mathieu Desnoyers's message of July 17, 2020 11:42 pm:
>>> - On Jul 16, 2020, at 7:26 PM, Nicholas Piggin npig...@gmail.com
- On Jul 19, 2020, at 11:03 PM, Nicholas Piggin npig...@gmail.com wrote:
> Excerpts from Mathieu Desnoyers's message of July 17, 2020 11:42 pm:
>> - On Jul 16, 2020, at 7:26 PM, Nicholas Piggin npig...@gmail.com wrote:
>> [...]
>>>
>>> membarrier does replace barrier instructions on
Excerpts from Mathieu Desnoyers's message of July 17, 2020 11:42 pm:
> - On Jul 16, 2020, at 7:26 PM, Nicholas Piggin npig...@gmail.com wrote:
> [...]
>>
>> membarrier does replace barrier instructions on remote CPUs, which do
>> order accesses performed by the kernel on the user address
- On Jul 17, 2020, at 1:44 PM, Alan Stern st...@rowland.harvard.edu wrote:
> On Fri, Jul 17, 2020 at 12:22:49PM -0400, Mathieu Desnoyers wrote:
>> - On Jul 17, 2020, at 12:11 PM, Alan Stern st...@rowland.harvard.edu
>> wrote:
>>
>> >> > I agree with Nick: A memory barrier is needed
On Fri, Jul 17, 2020 at 12:22:49PM -0400, Mathieu Desnoyers wrote:
> - On Jul 17, 2020, at 12:11 PM, Alan Stern st...@rowland.harvard.edu
> wrote:
>
> >> > I agree with Nick: A memory barrier is needed somewhere between the
> >> > assignment at 6 and the return to user mode at 8. Otherwise
- On Jul 17, 2020, at 12:11 PM, Alan Stern st...@rowland.harvard.edu wrote:
>> > I agree with Nick: A memory barrier is needed somewhere between the
>> > assignment at 6 and the return to user mode at 8. Otherwise you end up
>> > with the Store Buffer pattern having a memory barrier on only
> > I agree with Nick: A memory barrier is needed somewhere between the
> > assignment at 6 and the return to user mode at 8. Otherwise you end up
> > with the Store Buffer pattern having a memory barrier on only one side,
> > and it is well known that this arrangement does not guarantee any
> >
- On Jul 17, 2020, at 10:51 AM, Alan Stern st...@rowland.harvard.edu wrote:
> On Fri, Jul 17, 2020 at 09:39:25AM -0400, Mathieu Desnoyers wrote:
>> - On Jul 16, 2020, at 5:24 PM, Alan Stern st...@rowland.harvard.edu
>> wrote:
>>
>> > On Thu, Jul 16, 2020 at 02:58:41PM -0400, Mathieu
On Fri, Jul 17, 2020 at 09:39:25AM -0400, Mathieu Desnoyers wrote:
> - On Jul 16, 2020, at 5:24 PM, Alan Stern st...@rowland.harvard.edu wrote:
>
> > On Thu, Jul 16, 2020 at 02:58:41PM -0400, Mathieu Desnoyers wrote:
> >> - On Jul 16, 2020, at 12:03 PM, Mathieu Desnoyers
> >>
- On Jul 16, 2020, at 7:26 PM, Nicholas Piggin npig...@gmail.com wrote:
[...]
>
> membarrier does replace barrier instructions on remote CPUs, which do
> order accesses performed by the kernel on the user address space. So
> membarrier should too I guess.
>
> Normal process context accesses
- On Jul 16, 2020, at 5:24 PM, Alan Stern st...@rowland.harvard.edu wrote:
> On Thu, Jul 16, 2020 at 02:58:41PM -0400, Mathieu Desnoyers wrote:
>> - On Jul 16, 2020, at 12:03 PM, Mathieu Desnoyers
>> mathieu.desnoy...@efficios.com wrote:
>>
>> > - On Jul 16, 2020, at 11:46 AM,
On Thu, Jul 16, 2020 at 02:58:41PM -0400, Mathieu Desnoyers wrote:
> - On Jul 16, 2020, at 12:03 PM, Mathieu Desnoyers
> mathieu.desnoy...@efficios.com wrote:
>
> > - On Jul 16, 2020, at 11:46 AM, Mathieu Desnoyers
> > mathieu.desnoy...@efficios.com wrote:
> >
> >> - On Jul 16,
Excerpts from Mathieu Desnoyers's message of July 17, 2020 4:58 am:
> - On Jul 16, 2020, at 12:03 PM, Mathieu Desnoyers
> mathieu.desnoy...@efficios.com wrote:
>
>> - On Jul 16, 2020, at 11:46 AM, Mathieu Desnoyers
>> mathieu.desnoy...@efficios.com wrote:
>>
>>> - On Jul 16, 2020,
Excerpts from pet...@infradead.org's message of July 16, 2020 9:00 pm:
> On Thu, Jul 16, 2020 at 08:03:36PM +1000, Nicholas Piggin wrote:
>> Excerpts from Peter Zijlstra's message of July 16, 2020 6:50 pm:
>> > On Wed, Jul 15, 2020 at 10:18:20PM -0700, Andy Lutomirski wrote:
>> >> > On Jul 15,
- On Jul 16, 2020, at 12:03 PM, Mathieu Desnoyers
mathieu.desnoy...@efficios.com wrote:
> - On Jul 16, 2020, at 11:46 AM, Mathieu Desnoyers
> mathieu.desnoy...@efficios.com wrote:
>
>> - On Jul 16, 2020, at 12:42 AM, Nicholas Piggin npig...@gmail.com wrote:
>>> I should be more
- On Jul 16, 2020, at 11:46 AM, Mathieu Desnoyers
mathieu.desnoy...@efficios.com wrote:
> - On Jul 16, 2020, at 12:42 AM, Nicholas Piggin npig...@gmail.com wrote:
>> I should be more complete here, especially since I was complaining
>> about unclear barrier comment :)
>>
>>
>> CPU0
- On Jul 16, 2020, at 12:42 AM, Nicholas Piggin npig...@gmail.com wrote:
> I should be more complete here, especially since I was complaining
> about unclear barrier comment :)
>
>
> CPU0 CPU1
> a. user stuff1. user stuff
> b. membarrier() 2. enter
- On Jul 16, 2020, at 7:00 AM, Peter Zijlstra pet...@infradead.org wrote:
> On Thu, Jul 16, 2020 at 08:03:36PM +1000, Nicholas Piggin wrote:
>> Excerpts from Peter Zijlstra's message of July 16, 2020 6:50 pm:
>> > On Wed, Jul 15, 2020 at 10:18:20PM -0700, Andy Lutomirski wrote:
>> >> > On Jul
On Thu, Jul 16, 2020 at 08:03:36PM +1000, Nicholas Piggin wrote:
> Excerpts from Peter Zijlstra's message of July 16, 2020 6:50 pm:
> > On Wed, Jul 15, 2020 at 10:18:20PM -0700, Andy Lutomirski wrote:
> >> > On Jul 15, 2020, at 9:15 PM, Nicholas Piggin wrote:
> >> But I’m wondering if all this
Excerpts from Peter Zijlstra's message of July 16, 2020 6:50 pm:
> On Wed, Jul 15, 2020 at 10:18:20PM -0700, Andy Lutomirski wrote:
>> > On Jul 15, 2020, at 9:15 PM, Nicholas Piggin wrote:
>
>> > CPU0 CPU1
>> > 1. user stuff
>> > a. membarrier()
On Wed, Jul 15, 2020 at 10:18:20PM -0700, Andy Lutomirski wrote:
> > On Jul 15, 2020, at 9:15 PM, Nicholas Piggin wrote:
> > CPU0 CPU1
> > 1. user stuff
> > a. membarrier() 2. enter kernel
> > b. read rq->curr 3. rq->curr switched to
Excerpts from Andy Lutomirski's message of July 16, 2020 3:18 pm:
>
>
>> On Jul 15, 2020, at 9:15 PM, Nicholas Piggin wrote:
>>
>> Excerpts from Mathieu Desnoyers's message of July 14, 2020 12:13 am:
>>> - On Jul 13, 2020, at 9:47 AM, Nicholas Piggin npig...@gmail.com wrote:
>>>
> On Jul 15, 2020, at 9:15 PM, Nicholas Piggin wrote:
>
> Excerpts from Mathieu Desnoyers's message of July 14, 2020 12:13 am:
>> - On Jul 13, 2020, at 9:47 AM, Nicholas Piggin npig...@gmail.com wrote:
>>
>>> Excerpts from Nicholas Piggin's message of July 13, 2020 2:45 pm:
Excerpts from Nicholas Piggin's message of July 16, 2020 2:15 pm:
> Excerpts from Mathieu Desnoyers's message of July 14, 2020 12:13 am:
>> - On Jul 13, 2020, at 9:47 AM, Nicholas Piggin npig...@gmail.com wrote:
>>
>>> Excerpts from Nicholas Piggin's message of July 13, 2020 2:45 pm:
Excerpts from Mathieu Desnoyers's message of July 14, 2020 12:13 am:
> - On Jul 13, 2020, at 9:47 AM, Nicholas Piggin npig...@gmail.com wrote:
>
>> Excerpts from Nicholas Piggin's message of July 13, 2020 2:45 pm:
>>> Excerpts from Andy Lutomirski's message of July 11, 2020 3:04 am:
Excerpts from Andy Lutomirski's message of July 14, 2020 1:48 am:
> On Mon, Jul 13, 2020 at 7:13 AM Mathieu Desnoyers
> wrote:
>>
>> - On Jul 13, 2020, at 9:47 AM, Nicholas Piggin npig...@gmail.com wrote:
>>
>> > Excerpts from Nicholas Piggin's message of July 13, 2020 2:45 pm:
>> >> Excerpts
On Mon, Jul 13, 2020 at 7:13 AM Mathieu Desnoyers
wrote:
>
> - On Jul 13, 2020, at 9:47 AM, Nicholas Piggin npig...@gmail.com wrote:
>
> > Excerpts from Nicholas Piggin's message of July 13, 2020 2:45 pm:
> >> Excerpts from Andy Lutomirski's message of July 11, 2020 3:04 am:
> >>> Also, as it
- On Jul 13, 2020, at 9:47 AM, Nicholas Piggin npig...@gmail.com wrote:
> Excerpts from Nicholas Piggin's message of July 13, 2020 2:45 pm:
>> Excerpts from Andy Lutomirski's message of July 11, 2020 3:04 am:
>>> Also, as it stands, I can easily see in_irq() ceasing to promise to
>>>
Excerpts from Nicholas Piggin's message of July 13, 2020 2:45 pm:
> Excerpts from Andy Lutomirski's message of July 11, 2020 3:04 am:
>> Also, as it stands, I can easily see in_irq() ceasing to promise to
>> serialize. There are older kernels for which it does not promise to
>> serialize. And I
Excerpts from Andy Lutomirski's message of July 11, 2020 3:04 am:
> On Thu, Jul 9, 2020 at 6:57 PM Nicholas Piggin wrote:
>>
>> And get rid of the generic sync_core_before_usermode facility.
>>
>> This helper is the wrong way around I think. The idea that membarrier
>> state requires a core sync
On Thu, Jul 9, 2020 at 6:57 PM Nicholas Piggin wrote:
>
> And get rid of the generic sync_core_before_usermode facility.
>
> This helper is the wrong way around I think. The idea that membarrier
> state requires a core sync before returning to user is the easy one
> that does not need hiding
- On Jul 9, 2020, at 9:56 PM, Nicholas Piggin npig...@gmail.com wrote:
> And get rid of the generic sync_core_before_usermode facility.
>
> This helper is the wrong way around I think. The idea that membarrier
> state requires a core sync before returning to user is the easy one
> that does
On Fri, Jul 10, 2020 at 11:56:43AM +1000, Nicholas Piggin wrote:
> And get rid of the generic sync_core_before_usermode facility.
>
> This helper is the wrong way around I think. The idea that membarrier
> state requires a core sync before returning to user is the easy one
> that does not need
And get rid of the generic sync_core_before_usermode facility.
This helper is the wrong way around I think. The idea that membarrier
state requires a core sync before returning to user is the easy one
that does not need hiding behind membarrier calls. The gap in core
synchronization due to x86's
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