46 lines
2.9 KiB
ReStructuredText
46 lines
2.9 KiB
ReStructuredText
=========================
|
|
Thread Local Storage
|
|
=========================
|
|
|
|
Thread local storage (TLS) is a mechanism that allows each thread to have its own
|
|
copy of a variable. This is useful for variables that are used by multiple
|
|
functions in a thread, but should not be shared with other threads.
|
|
|
|
There are some approaches to using TLS in NuttX:
|
|
|
|
1. Use the ``pthread_key_create()`` and ``pthread_setspecific()`` that from the POSIX standard. This is the most portable approach, but it requires that
|
|
the platform support pthreads.
|
|
2. Use the ``thread_local`` or ``__thread`` keyword from the C standard: https://gcc.gnu.org/onlinedocs/gcc/extensions-to-the-c-language-family/thread-local-storage.html
|
|
|
|
Configuration
|
|
=============
|
|
|
|
.. code-block:: console
|
|
|
|
CONFIG_SCHED_THREAD_LOCAL /* Enable native thread local storage support */
|
|
|
|
|
|
Enable it to support native thread local storage, which is required that the compiler configured with ``--enable-tls`` option, this approach is more efficient if the compiler support it.
|
|
|
|
If your compiler support it then you still need further configuration to use it:
|
|
|
|
1. Enable ``CONFIG_SCHED_THREAD_LOCAL`` in menuconfig
|
|
2. Handle ``tbss`` and ``tdata`` sections in linker script, your can refer to the example in rv-virt
|
|
|
|
To confirm that your compiler supports TLS, you can try this command:
|
|
|
|
.. code-block:: console
|
|
|
|
arm-none-eabi-gcc --verbose
|
|
COLLECT_GCC=arm-none-eabi-gcc
|
|
COLLECT_LTO_WRAPPER=/home/huang/.local/pkg/arm/bin/../libexec/gcc/arm-none-eabi/13.3.1/lto-wrapper
|
|
Target: arm-none-eabi
|
|
Configured with: /data/jenkins/workspace/GNU-toolchain/arm-13/src/gcc/configure --target=arm-none-eabi --prefix=/data/jenkins/workspace/GNU-toolchain/arm-13/build-arm-none-eabi/install --with-gmp=/data/jenkins/workspace/GNU-toolchain/arm-13/build-arm-none-eabi/host-tools --with-mpfr=/data/jenkins/workspace/GNU-toolchain/arm-13/build-arm-none-eabi/host-tools --with-mpc=/data/jenkins/workspace/GNU-toolchain/arm-13/build-arm-none-eabi/host-tools --with-isl=/data/jenkins/workspace/GNU-toolchain/arm-13/build-arm-none-eabi/host-tools --disable-shared --disable-nls --disable-threads --disable-tls --enable-checking=release --enable-languages=c,c++,fortran --with-newlib --with-gnu-as --with-headers=yes --with-gnu-ld --with-native-system-header-dir=/include --with-sysroot=/data/jenkins/workspace/GNU-toolchain/arm-13/build-arm-none-eabi/install/arm-none-eabi --with-multilib-list=aprofile,rmprofile --with-pkgversion='Arm GNU Toolchain 13.3.Rel1 (Build arm-13.24)' --with-bugurl=https://bugs.linaro.org/
|
|
Thread model: single
|
|
Supported LTO compression algorithms: zlib
|
|
gcc version 13.3.1 20240614 (Arm GNU Toolchain 13.3.Rel1 (Build arm-13.24))
|
|
|
|
Then you can see ``--disable-tls`` in the output, which means that your compiler does not support TLS.
|
|
|
|
In this case, you can still use the thread local relative keyword, but it would be implemented by libgcc's emutls.
|