# # For a description of the syntax of this configuration file, # see the file kconfig-language.txt in the NuttX tools repository. # menu "Thread Local Storage (TLS)" config TLS_ALIGNED bool "Require stack alignment" default y if BUILD_KERNEL default n if !BUILD_KERNEL ---help--- Aligned TLS works by fetching thread information from the beginning of the stack memory allocation. In order to do this, the memory must be aligned in such a way that the executing logic can simply mask the current stack pointer to get the beginning of the stack allocation. The advantage of using an aligned stack is no OS interface need be called to get the beginning of the stack. It is simply an AND operation on the current stack pointer. The disadvantages are that the alignment (1) causes memory fragmentation which can be a serious problem for memory limited systems, and (2) limits the maximum size of the stack. Any mask places a limit on the maximum size of the stack; stack sizes about that would map to an incorrect address. In general, CONFIG_TLS_ALIGNED is preferred for the KERNEL build where the virtualized stack address can be aligned with no implications to physical memory. In other builds, the unaligned stack implementation is usually superior. config TLS_LOG2_MAXSTACK int "Maximum stack size (log2)" default 13 range 11 24 depends on TLS_ALIGNED ---help--- This setting specifies the alignment of the stack as a power of 2: 11=2KB, 12=4KB, 13=8KB, etc. The exact alignment is not so critical except that (1) a very large value can cause you to run out of alignable memory (and fail memory allocations), and (2) smaller values will limit the maximum size of the stack (hence the naming of this configuration value). config TLS_NELEM int "Number of TLS elements" default 4 range 0 64 ---help--- The number of unique TLS elements. These can be accessed with the user library functions tls_get_value() and tls_set_value() and the OS interfaces tls_alloc() and tls_free(). NOTE that the special value of CONFIG_TLS_NELEM disables these TLS interfaces. config TLS_TASK_NELEM int "Number of Task Local Storage elements" default 0 range 0 64 ---help--- The number of unique Task Local Storage elements similar with Thread Local Storage. These can be accessed with task_tls_alloc/task_tls_get_value/task_tls_set_value. NOTE that the 0 value of CONFIG_SCHED_TLS_NELEM disables these TLS interfaces. endmenu # Thread Local Storage (TLS)