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-rw-r--r--include/linux/sched/mm.h5
-rw-r--r--kernel/exit.c16
-rw-r--r--kernel/sched/membarrier.c12
3 files changed, 32 insertions, 1 deletions
diff --git a/include/linux/sched/mm.h b/include/linux/sched/mm.h
index d5ece7a9a403..a91fb3ad9ec7 100644
--- a/include/linux/sched/mm.h
+++ b/include/linux/sched/mm.h
@@ -347,6 +347,8 @@ static inline void membarrier_mm_sync_core_before_usermode(struct mm_struct *mm)
extern void membarrier_exec_mmap(struct mm_struct *mm);
+extern void membarrier_update_current_mm(struct mm_struct *next_mm);
+
#else
#ifdef CONFIG_ARCH_HAS_MEMBARRIER_CALLBACKS
static inline void membarrier_arch_switch_mm(struct mm_struct *prev,
@@ -361,6 +363,9 @@ static inline void membarrier_exec_mmap(struct mm_struct *mm)
static inline void membarrier_mm_sync_core_before_usermode(struct mm_struct *mm)
{
}
+static inline void membarrier_update_current_mm(struct mm_struct *next_mm)
+{
+}
#endif
#endif /* _LINUX_SCHED_MM_H */
diff --git a/kernel/exit.c b/kernel/exit.c
index 87a2d515de0d..a3dd6b36f99a 100644
--- a/kernel/exit.c
+++ b/kernel/exit.c
@@ -475,10 +475,24 @@ static void exit_mm(void)
BUG_ON(mm != current->active_mm);
/* more a memory barrier than a real lock */
task_lock(current);
+ /*
+ * When a thread stops operating on an address space, the loop
+ * in membarrier_private_expedited() may not observe that
+ * tsk->mm, and the loop in membarrier_global_expedited() may
+ * not observe a MEMBARRIER_STATE_GLOBAL_EXPEDITED
+ * rq->membarrier_state, so those would not issue an IPI.
+ * Membarrier requires a memory barrier after accessing
+ * user-space memory, before clearing tsk->mm or the
+ * rq->membarrier_state.
+ */
+ smp_mb__after_spinlock();
+ local_irq_disable();
current->mm = NULL;
- mmap_read_unlock(mm);
+ membarrier_update_current_mm(NULL);
enter_lazy_tlb(mm, current);
+ local_irq_enable();
task_unlock(current);
+ mmap_read_unlock(mm);
mm_update_next_owner(mm);
mmput(mm);
if (test_thread_flag(TIF_MEMDIE))
diff --git a/kernel/sched/membarrier.c b/kernel/sched/membarrier.c
index e23e74d52db5..aac329258af0 100644
--- a/kernel/sched/membarrier.c
+++ b/kernel/sched/membarrier.c
@@ -76,6 +76,18 @@ void membarrier_exec_mmap(struct mm_struct *mm)
this_cpu_write(runqueues.membarrier_state, 0);
}
+void membarrier_update_current_mm(struct mm_struct *next_mm)
+{
+ struct rq *rq = this_rq();
+ int membarrier_state = 0;
+
+ if (next_mm)
+ membarrier_state = atomic_read(&next_mm->membarrier_state);
+ if (READ_ONCE(rq->membarrier_state) == membarrier_state)
+ return;
+ WRITE_ONCE(rq->membarrier_state, membarrier_state);
+}
+
static int membarrier_global_expedited(void)
{
int cpu;