On Mon, Nov 07, 2016 at 06:10:14PM +0000, Mathieu Desnoyers wrote:
>
> ----- On Nov 7, 2016, at 1:06 PM, Paul E. McKenney paulmck@xxxxxxxxxxxxxxxxxx wrote:
>
> > On Mon, Nov 07, 2016 at 05:08:59PM +0000, Mathieu Desnoyers wrote:
> >> ----- On Nov 3, 2016, at 1:49 PM, Paul E. McKenney paulmck@xxxxxxxxxxxxxxxxxx
> >> wrote:
> >>
> >> > On Thu, Nov 03, 2016 at 10:29:28AM -0600, Mathieu Desnoyers wrote:
> >> >> Userspace applications should be allowed to expect the membarrier system
> >> >> call with MEMBARRIER_CMD_SHARED command to issue memory barriers on
> >> >> nohz_full CPUs, but synchronize_sched() does not take those into
> >> >> account.
> >> >>
> >> >> Given that we do not want unrelated processes to be able to affect
> >> >> real-time sensitive nohz_full CPUs, simply return ENOSYS when membarrier
> >> >> is invoked on a kernel with enabled nohz_full CPUs.
> >> >>
> >> >> Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@xxxxxxxxxxxx>
> >> >> CC: "Paul E. McKenney" <paulmck@xxxxxxxxxxxxxxxxxx>
> >> >
> >> > Acked-by: "Paul E. McKenney" <paulmck@xxxxxxxxxxxxxxxxxx>
> >>
> >> Hi Paul,
> >>
> >> Do you plan to pick it up through your tree, or I should sent
> >> it directly to Linus ?
> >
> > Your choice. I believe that the original went some other way, but I
> > would be fine carrying this one.
>
> Not sure what you mean by "the original" ? And which other way ?
> I have not been notified about this.
If I remember correctly, you sent the original sys_membarrier()
patch through akpm or similar.
> If you can carry this patch it would be very much appreciated,
Will do!
Thanx, Paul
> Thanks,
>
> Mathieu
>
> >
> > Thanx, Paul
> >
> >> Thanks,
> >>
> >> Mathieu
> >>
> >> >
> >> >> CC: Josh Triplett <josh@xxxxxxxxxxxxxxxx>
> >> >> CC: Steven Rostedt <rostedt@xxxxxxxxxxx>
> >> >> CC: Lai Jiangshan <jiangshanlai@xxxxxxxxx>
> >> >> CC: <stable@xxxxxxxxxxxxxxx> [3.10+]
> >> >> ---
> >> >> kernel/membarrier.c | 4 ++++
> >> >> 1 file changed, 4 insertions(+)
> >> >>
> >> >> diff --git a/kernel/membarrier.c b/kernel/membarrier.c
> >> >> index 536c727..9f9284f 100644
> >> >> --- a/kernel/membarrier.c
> >> >> +++ b/kernel/membarrier.c
> >> >> @@ -16,6 +16,7 @@
> >> >>
> >> >> #include <linux/syscalls.h>
> >> >> #include <linux/membarrier.h>
> >> >> +#include <linux/tick.h>
> >> >>
> >> >> /*
> >> >> * Bitmask made from a "or" of all commands within enum membarrier_cmd,
> >> >> @@ -51,6 +52,9 @@
> >> >> */
> >> >> SYSCALL_DEFINE2(membarrier, int, cmd, int, flags)
> >> >> {
> >> >> + /* MEMBARRIER_CMD_SHARED is not compatible with nohz_full. */
> >> >> + if (tick_nohz_full_enabled())
> >> >> + return -ENOSYS;
> >> >> if (unlikely(flags))
> >> >> return -EINVAL;
> >> >> switch (cmd) {
> >> >> --
> >> >> 2.1.4
> >>
> >> --
> >> Mathieu Desnoyers
> >> EfficiOS Inc.
> >> http://www.efficios.com
>
> --
> Mathieu Desnoyers
> EfficiOS Inc.
> http://www.efficios.com
>
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