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| author | Mathieu Desnoyers <mathieu.desnoyers@efficios.com> | 2016-11-03 17:29:28 +0100 |
|---|---|---|
| committer | Paul E. McKenney <paulmck@linux.vnet.ibm.com> | 2017-01-23 20:32:16 +0100 |
| commit | 907565337ebf998a68cb5c5b2174ce5e5da065eb (patch) | |
| tree | 5e5e3a5e43b3755f906bbc26bd20da6dd1dbe878 /kernel/membarrier.c | |
| parent | lockdep: Make RCU suspicious-access splats use pr_err (diff) | |
| download | linux-907565337ebf998a68cb5c5b2174ce5e5da065eb.tar.xz linux-907565337ebf998a68cb5c5b2174ce5e5da065eb.zip | |
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 <mathieu.desnoyers@efficios.com>
CC: Josh Triplett <josh@joshtriplett.org>
CC: Steven Rostedt <rostedt@goodmis.org>
CC: <stable@vger.kernel.org> [3.10+]
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Chris Metcalf <cmetcalf@mellanox.com>
Cc: Rik van Riel <riel@redhat.com>
Acked-by: Lai Jiangshan <jiangshanlai@gmail.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>
Diffstat (limited to 'kernel/membarrier.c')
| -rw-r--r-- | kernel/membarrier.c | 4 |
1 files changed, 4 insertions, 0 deletions
diff --git a/kernel/membarrier.c b/kernel/membarrier.c index 536c727a56e9..9f9284f37f8d 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) { |