From 234af6aaa2ec2fd5c8c758a8f9fa29553ddeaf3f Mon Sep 17 00:00:00 2001
From: shaojinchun <shaojinchun@rt-thread.com>
Date: Fri, 11 Oct 2019 09:13:40 +0800
Subject: [PATCH] =?UTF-8?q?=E4=BF=AE=E6=AD=A3=E7=9B=B8=E5=90=8C=E4=BC=98?=
 =?UTF-8?q?=E5=85=88=E7=BA=A7=E4=BB=BB=E5=8A=A1=E5=88=87=E6=8D=A2=E5=A4=AA?=
 =?UTF-8?q?=E9=A2=91=E7=B9=81=E7=9A=84=E9=97=AE=E9=A2=98?=
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---
 include/rtdef.h |  1 +
 src/clock.c     |  2 ++
 src/scheduler.c | 15 +++++++++++++++
 src/thread.c    |  1 +
 4 files changed, 19 insertions(+)

diff --git a/include/rtdef.h b/include/rtdef.h
index 3dc8a2a2a9..90604e9b1d 100644
--- a/include/rtdef.h
+++ b/include/rtdef.h
@@ -608,6 +608,7 @@ struct rt_thread
 
     rt_ubase_t  init_tick;                              /**< thread's initialized tick */
     rt_ubase_t  remaining_tick;                         /**< remaining tick */
+    rt_ubase_t  can_yield;                              /**< indicate whether remaining_tick has been reloaded since last schedule */
 
     struct rt_timer thread_timer;                       /**< built-in thread timer */
 
diff --git a/src/clock.c b/src/clock.c
index a652282b6e..d56f4b00f3 100644
--- a/src/clock.c
+++ b/src/clock.c
@@ -89,6 +89,8 @@ void rt_tick_increase(void)
         /* change to initialized tick */
         thread->remaining_tick = thread->init_tick;
 
+        thread->can_yield = 1;
+
         /* yield */
         rt_thread_yield();
     }
diff --git a/src/scheduler.c b/src/scheduler.c
index f671a49623..a4b4800d76 100644
--- a/src/scheduler.c
+++ b/src/scheduler.c
@@ -344,8 +344,13 @@ void rt_schedule(void)
                 {
                     to_thread = current_thread;
                 }
+                else if (current_thread->current_priority == highest_ready_priority && current_thread->can_yield == 0)
+                {
+                    to_thread = current_thread;
+                }
                 else
                 {
+                    current_thread->can_yield = 0;
                     rt_schedule_insert_thread(current_thread);
                 }
             }
@@ -435,8 +440,13 @@ void rt_schedule(void)
                 {
                     to_thread = rt_current_thread;
                 }
+                else if (current_thread->current_priority == highest_ready_priority && current_thread->can_yield == 0)
+                {
+                    to_thread = current_thread;
+                }
                 else
                 {
+                    current_thread->can_yield = 0;
                     need_insert_from_thread = 1;
                 }
             }
@@ -578,8 +588,13 @@ void rt_scheduler_do_irq_switch(void *context)
                 {
                     to_thread = current_thread;
                 }
+                else if (current_thread->current_priority == highest_ready_priority && current_thread->can_yield == 0)
+                {
+                    to_thread = current_thread;
+                }
                 else
                 {
+                    current_thread->can_yield = 0;
                     rt_schedule_insert_thread(current_thread);
                 }
             }
diff --git a/src/thread.c b/src/thread.c
index a88729e52c..cf42c72a1b 100644
--- a/src/thread.c
+++ b/src/thread.c
@@ -159,6 +159,7 @@ static rt_err_t _rt_thread_init(struct rt_thread *thread,
     /* tick init */
     thread->init_tick      = tick;
     thread->remaining_tick = tick;
+    thread->can_yield      = 0;
 
     /* error and flags */
     thread->error = RT_EOK;