Dynamic thread memory leakage

[jdoe95]

Memory not released after dynamic thread exits.

Replication:

• Call os_memory_get_pool_info to obtain pool size: 27468
• Create a thread using os_thread_create
• Thread may or may not call os_memory_allocate and os_memory_free
• Thread exits
• Call os_memory_get_pool_info again to obtain pool size: 26352

static void user_thread(void)
{
	ushell_printf(TTY_WARN "Dynamic thread started.\n\r" );
	for(unsigned i = 0; i < 10; i++ )
	{
		ushell_printf(TTY_INFO "Hello %u\n\r", i);
		os_thread_delay(100);
	}

	ushell_printf(TTY_WARN "Dynamic thread exiting...\n\r" );
}

void cmd_create_thread( char *argv[], int argc )
{
	(void)argv;
	(void)argc;
	ushell_printf(TTY_INFO "running os_thread_create...\n\r" );
	os_thread_create(2, 1024, user_thread);
}

ushell version 0.2
> 
help
info
lscmd
exit
args
demo
poolinfo
> poolinfo
num blocks in pool 1
pool size 27468

> demo
[INFO]  running os_thread_create...

> [WARN]  Dynamic thread started.
[INFO]  Hello 0
[INFO]  Hello 1
[INFO]  Hello 2
[INFO]  Hello 3
[INFO]  Hello 4
[INFO]  Hello 5
[INFO]  Hello 6
[INFO]  Hello 7
[INFO]  Hello 8
[INFO]  Hello 9
[WARN]  Dynamic thread exiting...

> poolinfo
num blocks in pool 1
pool size 26352

> 

[jdoe95]

The problem is found here

mrtos/source/thread.c

Line 975 in d18e268

thd_delete_static( p_thd, &g_sch);

After exiting, dynamic thread jumps to thd_return_hook and then calls os_thread_delete(0) to delete itself.
thd_return_hook
↘️ os_thread_delete(0)
↘️ thd_delete_static() (to remove itself from the ready queue)
↘️ sch_unload_current()

In sch_unload_current() a natural preemption window is opened, and other threads preempts this one immediately. And since current thread was removed from the ready list by thd_delete_static, it never resumes. Memory deallocation only happens after the thread resumes from sch_unload_current()