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sched/sched: simplify the implementation of the function nxsched_readytorun_setpriority

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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

reason:
If the type of tcb is TSTATE_TASK_ASSIGNED, removing it using nxsched_remove_not_running
and then putting it back into the queue may result in a context switch.

Signed-off-by: hujun5 <hujun5@xiaomi.com>
This commit is contained in:
hujun5 2024-08-19 21:08:55 +08:00 • committed by Xiang Xiao
parent 1c5a0bf6cc
commit 1e57a5653c
1 changed files with 3 additions and 73 deletions
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76
sched/sched/sched_setpriority.c
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@ -212,83 +212,13 @@ static void nxsched_readytorun_setpriority(FAR struct tcb_s *tcb,
{
FAR struct tcb_s *rtcb;
#ifdef CONFIG_SMP
int cpu;
/* CASE 2a. The task is ready-to-run (but not running) but not assigned to
* a CPU. An increase in priority could cause a context switch may be
* caused by the re-prioritization. The task is not assigned and may run
* on any CPU.
*/
if (tcb->task_state == TSTATE_TASK_READYTORUN)
{
cpu = nxsched_select_cpu(tcb->affinity);
}
/* CASE 2b. The task is ready to run, and assigned to a CPU. An increase
* in priority could cause this task to become running but the task can
* only run on its assigned CPU.
*/
else
{
cpu = tcb->cpu;
}
/* The running task is the task at the head of the g_assignedtasks[]
* associated with the selected CPU.
*/
rtcb = current_task(cpu);
#else
/* CASE 2. The task is ready-to-run (but not running) and a context switch
* may be caused by the re-prioritization.
*/
rtcb = this_task();
#endif
/* A context switch will occur if the new priority of the ready-to-run
* task is (strictly) greater than the current running task
*/
/* A context switch will occur. */
if (sched_priority > rtcb->sched_priority)
if (nxsched_reprioritize_rtr(tcb, sched_priority))
{
/* A context switch will occur. */
if (nxsched_reprioritize_rtr(tcb, sched_priority))
{
up_switch_context(this_task(), rtcb);
}
}
/* Otherwise, we can just change priority and re-schedule (since it have
* no other effect).
*/
else
{
/* Remove the TCB from the ready-to-run task list that it resides in.
* It should not be at the head of the list.
*/
bool check = nxsched_remove_readytorun(tcb, false);
DEBUGASSERT(check == false);
UNUSED(check);
/* Change the task priority */
tcb->sched_priority = (uint8_t)sched_priority;
/* Put it back into the correct ready-to-run task list. It must not
* end up at the head of the list.
*/
check = nxsched_add_readytorun(tcb);
DEBUGASSERT(check == false);
UNUSED(check);
up_switch_context(this_task(), rtcb);
}
}