On Tue, Aug 25, 2020 at 9:58 AM Mathieu Desnoyers
wrote:
>
[...]
>
> Concretely speaking, let's just add a new membarrier command for the use-case
> at hand. All other ways of doing things we have discussed are tricky to expose
> in a way that is discoverable by user-space through the QUERY comman
- On Aug 20, 2020, at 1:42 PM, Peter Oskolkov p...@posk.io wrote:
> On Wed, Aug 12, 2020 at 12:44 PM Mathieu Desnoyers
> wrote:
>>
> [...]
>>
>> > One way of doing what you suggest is to allow some commands to be
>> > bitwise-ORed.
>> >
>> > So, for example, the user could call
>> >
>> > mem
On Wed, Aug 12, 2020 at 12:44 PM Mathieu Desnoyers
wrote:
>
[...]
>
> > One way of doing what you suggest is to allow some commands to be
> > bitwise-ORed.
> >
> > So, for example, the user could call
> >
> > membarrier(CMD_PRIVATE_EXPEDITED_SYNC_CORE | CMD_PRIVATE_EXPEDITED_RSEQ,
> > cpu_id)
>
- On Aug 12, 2020, at 2:48 PM, Peter Oskolkov p...@posk.io wrote:
> On Wed, Aug 12, 2020 at 11:30 AM Mathieu Desnoyers
> wrote:
>
> [...]
>
>> "flags" is there to allow extensibility without requiring to add new
>> membarrier commands for every change. Even though it is not used now,
>> I d
On Wed, Aug 12, 2020 at 11:30 AM Mathieu Desnoyers
wrote:
[...]
> "flags" is there to allow extensibility without requiring to add new
> membarrier commands for every change. Even though it is not used now,
> I don't think re-purposing it is a good idea. What is wrong with just
> adding an addit
- On Aug 11, 2020, at 5:08 PM, Peter Oskolkov p...@posk.io wrote:
> On Mon, Aug 10, 2020 at 11:27 PM Peter Zijlstra wrote:
>>
>> On Mon, Aug 10, 2020 at 05:09:58PM -0700, Peter Oskolkov wrote:
>> > @@ -27,6 +35,12 @@
>> >
>> > static void ipi_mb(void *info)
>> > {
>>
>> The #ifdef wants
On Mon, Aug 10, 2020 at 11:27 PM Peter Zijlstra wrote:
>
> On Mon, Aug 10, 2020 at 05:09:58PM -0700, Peter Oskolkov wrote:
> > @@ -27,6 +35,12 @@
> >
> > static void ipi_mb(void *info)
> > {
>
> The #ifdef wants to behere, otherwise you'll get a compile warning for
> !RSEQ builds.
Ack. Will do
On Tue, Aug 11, 2020 at 08:27:33AM +0200, Peter Zijlstra wrote:
> SYSCALL_DEFINE2(membarrier, int, cmd, int, flags)
> {
> + int cflags = 0, int cpuid = -1;
> +
> if (unlikely(flags) && cmd != MEMBARRIER_CMD_PRIVATE_EXPEDITED_RSEQ)
> return -EINVAL;
> +
> + if (cmd & (M
On Mon, Aug 10, 2020 at 05:09:58PM -0700, Peter Oskolkov wrote:
> @@ -27,6 +35,12 @@
>
> static void ipi_mb(void *info)
> {
The #ifdef wants to behere, otherwise you'll get a compile warning for
!RSEQ builds.
> + int *flags = info;
> +
> +#ifdef CONFIG_RSEQ
> + if (flags && (*flags ==
This patchset is based on Google-internal RSEQ
work done by Paul Turner and Andrew Hunter.
When working with per-CPU RSEQ-based memory allocations,
it is sometimes important to make sure that a global
memory location is no longer accessed from RSEQ critical
sections. For example, there can be two
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