sched: add nxsched_remove_self

reason:
1In the scenario of active waiting, context switching is inevitable, and we can eliminate redundant judgments.

code size
before
hujun5@hujun5-OptiPlex-7070:~/downloads1/vela_sim/nuttx$ size nuttx
   text    data     bss     dec     hex filename
 262848   49985   63893  376726   5bf96 nuttx

after
hujun5@hujun5-OptiPlex-7070:~/downloads1/vela_sim/nuttx$ size nuttx
   text    data     bss     dec     hex filename
 263324   49985   63893  377202   5c172 nuttx

reduce code size by  -476

Configuring NuttX and compile:
$ ./tools/configure.sh -l qemu-armv8a:nsh_smp
$ make
Running with qemu
$ qemu-system-aarch64 -cpu cortex-a53 -smp 4 -nographic \
   -machine virt,virtualization=on,gic-version=3 \
   -net none -chardev stdio,id=con,mux=on -serial chardev:con \
   -mon chardev=con,mode=readline -kernel ./nuttx

Signed-off-by: hujun5 <hujun5@xiaomi.com>

Author: hujun260

sched/mqueue/mq_rcvinternal.c

@@ -138,7 +138,6 @@ int nxmq_wait_receive(FAR struct mqueue_inode_s *msgq,
 {
   FAR struct mqueue_msg_s *newmsg;
   FAR struct tcb_s *rtcb;
-  bool switch_needed;
 
   DEBUGASSERT(rcvmsg != NULL);
 
@@ -186,21 +185,18 @@ int nxmq_wait_receive(FAR struct mqueue_inode_s *msgq,
 
           DEBUGASSERT(!is_idle_task(rtcb));
 
-          /* Remove the tcb task from the ready-to-run list. */
+          /* Remove the tcb task from the running list. */
 
-          switch_needed = nxsched_remove_readytorun(rtcb, true);
+          nxsched_remove_self(rtcb);
 
           /* Add the task to the specified blocked task list */
 
           rtcb->task_state = TSTATE_WAIT_MQNOTEMPTY;
           nxsched_add_prioritized(rtcb, MQ_WNELIST(msgq->cmn));
 
-          /* Now, perform the context switch if one is needed */
+          /* Now, perform the context switch */
 
-          if (switch_needed)
-            {
-              up_switch_context(this_task(), rtcb);
-            }
+          up_switch_context(this_task(), rtcb);
 
           /* When we resume at this point, either (1) the message queue
            * is no longer empty, or (2) the wait has been interrupted by

sched/mqueue/mq_sndinternal.c

@@ -215,7 +215,6 @@ FAR struct mqueue_msg_s *nxmq_alloc_msg(void)
 int nxmq_wait_send(FAR struct mqueue_inode_s *msgq, int oflags)
 {
   FAR struct tcb_s *rtcb;
-  bool switch_needed;
 
 #ifdef CONFIG_CANCELLATION_POINTS
   /* nxmq_wait_send() is not a cancellation point, but may be called via
@@ -271,21 +270,18 @@ int nxmq_wait_send(FAR struct mqueue_inode_s *msgq, int oflags)
 
       DEBUGASSERT(!is_idle_task(rtcb));
 
-      /* Remove the tcb task from the ready-to-run list. */
+      /* Remove the tcb task from the running list. */
 
-      switch_needed = nxsched_remove_readytorun(rtcb, true);
+      nxsched_remove_self(rtcb);
 
       /* Add the task to the specified blocked task list */
 
       rtcb->task_state = TSTATE_WAIT_MQNOTFULL;
       nxsched_add_prioritized(rtcb, MQ_WNFLIST(msgq->cmn));
 
-      /* Now, perform the context switch if one is needed */
+      /* Now, perform the context switch */
 
-      if (switch_needed)
-        {
-          up_switch_context(this_task(), rtcb);
-        }
+      up_switch_context(this_task(), rtcb);
 
       /* When we resume at this point, either (1) the message queue
        * is no longer empty, or (2) the wait has been interrupted by

sched/mqueue/msgrcv.c

@@ -45,7 +45,6 @@ static int msgrcv_wait(FAR struct msgq_s *msgq, FAR struct msgbuf_s **rcvmsg,
   FAR struct msgbuf_s *newmsg = NULL;
   FAR struct msgbuf_s *tmp;
   FAR struct tcb_s *rtcb;
-  bool switch_needed;
 
 #ifdef CONFIG_CANCELLATION_POINTS
   /* msgrcv_wait() is not a cancellation point, but it may be called
@@ -129,21 +128,18 @@ static int msgrcv_wait(FAR struct msgq_s *msgq, FAR struct msgbuf_s **rcvmsg,
 
       DEBUGASSERT(NULL != rtcb->flink);
 
-      /* Remove the tcb task from the ready-to-run list. */
+      /* Remove the tcb task from the running list. */
 
-      switch_needed = nxsched_remove_readytorun(rtcb, true);
+      nxsched_remove_self(rtcb);
 
       /* Add the task to the specified blocked task list */
 
       rtcb->task_state = TSTATE_WAIT_MQNOTEMPTY;
       nxsched_add_prioritized(rtcb, MQ_WNELIST(msgq->cmn));
 
-      /* Now, perform the context switch if one is needed */
+      /* Now, perform the context switch */
 
-      if (switch_needed)
-        {
-          up_switch_context(this_task(), rtcb);
-        }
+      up_switch_context(this_task(), rtcb);
 
       /* When we resume at this point, either (1) the message queue
        * is no longer empty, or (2) the wait has been interrupted by

sched/mqueue/msgsnd.c

@@ -42,7 +42,6 @@
 static int msgsnd_wait(FAR struct msgq_s *msgq, int msgflg)
 {
   FAR struct tcb_s *rtcb;
-  bool switch_needed;
 
 #ifdef CONFIG_CANCELLATION_POINTS
   /* msgsnd_wait() is not a cancellation point, but may be called via
@@ -95,21 +94,18 @@ static int msgsnd_wait(FAR struct msgq_s *msgq, int msgflg)
 
       DEBUGASSERT(NULL != rtcb->flink);
 
-      /* Remove the tcb task from the ready-to-run list. */
+      /* Remove the tcb task from the running list. */
 
-      switch_needed = nxsched_remove_readytorun(rtcb, true);
+      nxsched_remove_self(rtcb);
 
       /* Add the task to the specified blocked task list */
 
       rtcb->task_state = TSTATE_WAIT_MQNOTFULL;
       nxsched_add_prioritized(rtcb, MQ_WNFLIST(msgq->cmn));
 
-      /* Now, perform the context switch if one is needed */
+      /* Now, perform the context switch */
 
-      if (switch_needed)
-        {
-          up_switch_context(this_task(), rtcb);
-        }
+      up_switch_context(this_task(), rtcb);
 
       /* When we resume at this point, either (1) the message queue
        * is no longer empty, or (2) the wait has been interrupted by

sched/paging/pg_miss.c

@@ -112,7 +112,6 @@ void pg_miss(void)
 {
   FAR struct tcb_s *ftcb = this_task();
   FAR struct tcb_s *wtcb;
-  bool switch_needed;
 
   /* Sanity checking
    *
@@ -138,21 +137,18 @@ void pg_miss(void)
 
   DEBUGASSERT(!is_idle_task(ftcb));
 
-  /* Remove the tcb task from the ready-to-run list. */
+  /* Remove the tcb task from the running list. */
 
-  switch_needed = nxsched_remove_readytorun(ftcb, true);
+  nxsched_remove_self(ftcb);
 
   /* Add the task to the specified blocked task list */
 
   ftcb->task_state = TSTATE_WAIT_PAGEFILL;
   nxsched_add_prioritized(ftcb, list_waitingforfill());
 
-  /* Now, perform the context switch if one is needed */
+  /* Now, perform the context switch */
 
-  if (switch_needed)
-    {
-      up_switch_context(this_task(), ftcb);
-    }
+  up_switch_context(this_task(), ftcb);
 
   /* Boost the page fill worker thread priority.
    * - Check the priority of the task at the head of the g_waitingforfill

sched/sched/sched.h

@@ -321,6 +321,7 @@ int nxthread_create(FAR const char *name, uint8_t ttype, int priority,
 
 bool nxsched_add_readytorun(FAR struct tcb_s *rtrtcb);
 bool nxsched_remove_readytorun(FAR struct tcb_s *rtrtcb, bool merge);
+void nxsched_remove_self(FAR struct tcb_s *rtrtcb);
 bool nxsched_add_prioritized(FAR struct tcb_s *tcb, DSEG dq_queue_t *list);
 void nxsched_merge_prioritized(FAR dq_queue_t *list1, FAR dq_queue_t *list2,
                                uint8_t task_state);