From: Mathieu Desnoyers mathieu.desnoyers@efficios.com
mainline inclusion from mainline-5.4-rc1 commit c6d68c1c4a4d6611fc0f8145d764226571d737ca category: bugfix bugzilla: 28332 CVE: NA
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If there is only a single mm_user for the mm, the private expedited membarrier command can skip the IPIs, because only a single thread is using the mm.
Signed-off-by: Mathieu Desnoyers mathieu.desnoyers@efficios.com Signed-off-by: Peter Zijlstra (Intel) peterz@infradead.org Cc: Chris Metcalf cmetcalf@ezchip.com Cc: Christoph Lameter cl@linux.com Cc: Eric W. Biederman ebiederm@xmission.com Cc: Kirill Tkhai tkhai@yandex.ru Cc: Linus Torvalds torvalds@linux-foundation.org Cc: Mike Galbraith efault@gmx.de Cc: Oleg Nesterov oleg@redhat.com Cc: Paul E. McKenney paulmck@linux.ibm.com Cc: Peter Zijlstra peterz@infradead.org Cc: Russell King - ARM Linux admin linux@armlinux.org.uk Cc: Thomas Gleixner tglx@linutronix.de Link: https://lkml.kernel.org/r/20190919173705.2181-7-mathieu.desnoyers@efficios.c... Signed-off-by: Ingo Molnar mingo@kernel.org Signed-off-by: Cheng Jian cj.chengjian@huawei.com Reviewed-By: Xie XiuQi xiexiuqi@huawei.com Signed-off-by: Yang Yingliang yangyingliang@huawei.com --- kernel/sched/membarrier.c | 9 +++++---- 1 file changed, 5 insertions(+), 4 deletions(-)
diff --git a/kernel/sched/membarrier.c b/kernel/sched/membarrier.c index dc25e83..5f68c54 100644 --- a/kernel/sched/membarrier.c +++ b/kernel/sched/membarrier.c @@ -154,20 +154,21 @@ static int membarrier_private_expedited(int flags) int cpu; bool fallback = false; cpumask_var_t tmpmask; + struct mm_struct *mm = current->mm;
if (flags & MEMBARRIER_FLAG_SYNC_CORE) { if (!IS_ENABLED(CONFIG_ARCH_HAS_MEMBARRIER_SYNC_CORE)) return -EINVAL; - if (!(atomic_read(¤t->mm->membarrier_state) & + if (!(atomic_read(&mm->membarrier_state) & MEMBARRIER_STATE_PRIVATE_EXPEDITED_SYNC_CORE_READY)) return -EPERM; } else { - if (!(atomic_read(¤t->mm->membarrier_state) & + if (!(atomic_read(&mm->membarrier_state) & MEMBARRIER_STATE_PRIVATE_EXPEDITED_READY)) return -EPERM; }
- if (num_online_cpus() == 1) + if (atomic_read(&mm->mm_users) == 1 || num_online_cpus() == 1) return 0;
/* @@ -203,7 +204,7 @@ static int membarrier_private_expedited(int flags) continue; rcu_read_lock(); p = task_rcu_dereference(&cpu_rq(cpu)->curr); - if (p && p->mm == current->mm) { + if (p && p->mm == mm) { if (!fallback) __cpumask_set_cpu(cpu, tmpmask); else