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-rw-r--r--include/linux/preempt.h18
-rw-r--r--kernel/context_tracking.c40
2 files changed, 57 insertions, 1 deletions
diff --git a/include/linux/preempt.h b/include/linux/preempt.h
index 87a03c746f17..f5d4723cdb3d 100644
--- a/include/linux/preempt.h
+++ b/include/linux/preempt.h
@@ -33,9 +33,25 @@ do { \
preempt_schedule(); \
} while (0)
+#ifdef CONFIG_CONTEXT_TRACKING
+
+void preempt_schedule_context(void);
+
+#define preempt_check_resched_context() \
+do { \
+ if (unlikely(test_thread_flag(TIF_NEED_RESCHED))) \
+ preempt_schedule_context(); \
+} while (0)
+#else
+
+#define preempt_check_resched_context() preempt_check_resched()
+
+#endif /* CONFIG_CONTEXT_TRACKING */
+
#else /* !CONFIG_PREEMPT */
#define preempt_check_resched() do { } while (0)
+#define preempt_check_resched_context() do { } while (0)
#endif /* CONFIG_PREEMPT */
@@ -88,7 +104,7 @@ do { \
do { \
preempt_enable_no_resched_notrace(); \
barrier(); \
- preempt_check_resched(); \
+ preempt_check_resched_context(); \
} while (0)
#else /* !CONFIG_PREEMPT_COUNT */
diff --git a/kernel/context_tracking.c b/kernel/context_tracking.c
index 65349f07b878..66677003e223 100644
--- a/kernel/context_tracking.c
+++ b/kernel/context_tracking.c
@@ -71,6 +71,46 @@ void user_enter(void)
local_irq_restore(flags);
}
+#ifdef CONFIG_PREEMPT
+/**
+ * preempt_schedule_context - preempt_schedule called by tracing
+ *
+ * The tracing infrastructure uses preempt_enable_notrace to prevent
+ * recursion and tracing preempt enabling caused by the tracing
+ * infrastructure itself. But as tracing can happen in areas coming
+ * from userspace or just about to enter userspace, a preempt enable
+ * can occur before user_exit() is called. This will cause the scheduler
+ * to be called when the system is still in usermode.
+ *
+ * To prevent this, the preempt_enable_notrace will use this function
+ * instead of preempt_schedule() to exit user context if needed before
+ * calling the scheduler.
+ */
+void __sched notrace preempt_schedule_context(void)
+{
+ struct thread_info *ti = current_thread_info();
+ enum ctx_state prev_ctx;
+
+ if (likely(ti->preempt_count || irqs_disabled()))
+ return;
+
+ /*
+ * Need to disable preemption in case user_exit() is traced
+ * and the tracer calls preempt_enable_notrace() causing
+ * an infinite recursion.
+ */
+ preempt_disable_notrace();
+ prev_ctx = exception_enter();
+ preempt_enable_no_resched_notrace();
+
+ preempt_schedule();
+
+ preempt_disable_notrace();
+ exception_exit(prev_ctx);
+ preempt_enable_notrace();
+}
+EXPORT_SYMBOL_GPL(preempt_schedule_context);
+#endif /* CONFIG_PREEMPT */
/**
* user_exit - Inform the context tracking that the CPU is