----- 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 you can carry this patch it would be very much appreciated, 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 -- To unsubscribe from this list: send the line "unsubscribe stable" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html