Fix: Disable sys_membarrier when nohz_full is enabled

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 <[email protected]>
CC: Josh Triplett <[email protected]>
CC: Steven Rostedt <[email protected]>
CC: <[email protected]>	[3.10+]
Signed-off-by: Paul E. McKenney <[email protected]>
Cc: Frederic Weisbecker <[email protected]>
Cc: Chris Metcalf <[email protected]>
Cc: Rik van Riel <[email protected]>
Acked-by: Lai Jiangshan <[email protected]>
Reviewed-by: Josh Triplett <[email protected]>

0 files changed, 0 insertions, 0 deletions