* Fix thread control bug about `RT_THREAD_CTRL_CLOSE` command
* Avoid deadlock (rt_hw_interrupt_disable and rt_enter_critical when enable smp)
* Fix the issue of judging the ready_table of pcpu when multi-core rt_schedule_remove_thread
* Fix the issue that the yield operation cannot release the cpu in time
* Fix the iterator failure for softtimer list timeout check
* Fix rt_timer_list_next_timeout multi-task safe
* Add timer working status query function to software timer
* Fix the software issue when the system timer thread is pending
* Fix the timer/software timer handling issue if the timeout function starts/stops/deletes this timer.
* Fix an issue with rt_timer_start being broken and destroying the timer list
* Fix the bug that the linked list is still mounted when the single timer is not modified
* Add function rt_tick_get_millisecond()
* Fix the delay_until issue
* Add mb mq value overflow-check code
* Fix the rt_event_recv function, if the event met without blocking, assigning thread->event_set/event_info will goes well
* Add the definition of the maximum value of ipc type
* Remove the call of rt_system_object_init/rt_system_tick_init from the code.
* Removes component configuration macro `RT_USING_FINSH` from the kernel
* Use object_find to implement thread_find/device_find
* The cleanup operation is executed before the current thread exits
## Components
* Fix assert in the sys_arch_mbox_fetch function when close socket
* Add dhcp start or stop function to start or stop dhcp.
* Change rt_data_queue_peak to rt_data_queue_peek.
* Update elmfat to R0.14 patch 1.
* Add SAL_INTERNET_CHECK configuration item to support turning on or off the network status check
* Solve the issue that the do_pollfd function processing the underlying network device returns error -1
* Fix the issue that when the network card device calls to close dhcp, the bottom layer no need to call the dhcp_stop function to close dhcp
* Add the function of judging the network card up and down in the sal_accept function
* Modify the spelling error of the macro definition, modify the printing error when printing the IMEI number
* Fix the issue that the server closed the connection when web socket requests the data that comes back from the server, and the socket status is incorrectly judged at that point
* Fix the issue of incorrect sal_getaddrinfo release when sal socket supports multiple network cards
* Update AT socket
* Support alloc socket dynamically with at device
* Update AT_SW_VERSION and adjust at_socket_ops
* Adjust where the AT socket callback function
* Fix at_client, avoid creating the same client repeatedly and prevent working exceptions and memory leaks.
* Fix the bug that rx_notice out of sync when the data is received after last rt_device_read() is zero
* [FinSH] rm command supports recursive deletion of folders
* Add clear command for FINSH
* [posix] Implement usleep function
* Fix the issue of pthreads compilation error when using the new version of newlib; at the same time solve the problem of pthreads under 64-bit;
* [dlmodule] Fix crash when dlmodule exits
* Add priority & stack_size param parsing for dlmodule
* libc adds getline/getdelim functions
* Change the header file included in some libc files from <rtthread.h> to <rtconfig.h> to narrow the scope of inclusion to prevent recursive compilation
* [jffs2] error check of rt_event_recv()
* Add rt_data_queue_deinit and fix bug of dataqueue
* Change log in device driver framework
* [pin] Add rt_pin_get to pin frame
* [PM] Update RT-Thread PM2.0 framework
* [audio] Fix compile warning, undefine var
* [serial] Fix the crash caused when the serial port receiving buffer is full and ULOG_USING_ISR_LOG is not turned on
* [wlan] Add raw frame send interface and Management frame filter interface
* [Sensor] Add vendor info and sensor types for cmd
* [Sensor] Support custom commands for rt_sensor_control
* [sensor] Support TOF sensor class
* [SFUD] Update the 'sf bench' command.
* [spi] Fix "response+1" causing hard fault of unaligned access to SPI memory of STM32 HAL library
* [RTC] Optimize RTC alarm function, add alarm function for SOFT_RTC
* [hwtimer] When getting the timer count, prevent overflow update due to the interruption
* [dirver/i2c] i2c driver supports bus lock, STOP control
* [usb] Fix bug in device descriptor that MAC OS enumeration failed
* Fix the bug that USB cannot recognize composite device normally
* Fix USB host core bugs
* Limit >4 USB ports hubs
* Double free intf
* dname buffer size is too small
* Reset child pointer after detaching instance
## BSP and CPU porting
* Add license info and code cleanup for vexpress-a9 BSP
* Add HDSC hc32f4a0 BSP support
* Add support for Cypress PSoC6 series products
* Fix the lpc55 issue under Linux/GCC
* [qemu] Fix spelling mistakes of code in drv_pl041.c
* [loongson] Update the SPI driver and UART driver on the Loongson 2K1000 platform
* [allwinner_tina]Fix spi driver bug
* [smartfusion2]Support Microsemi SmartFusion2 family FPGA
* [imxrt] Add ethernet configuration for imxrt1064-nxp-evk
* Add support for architecture sparc-v8 and soc bm3803.
