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The task stack could be deallocated later, but for fork()/exec() kind of workloads (say a shell script executing several commands) it is important that the stack is released in finish_task_switch() so that in VMAP_STACK case it can be cached and reused in the new task. For PREEMPT_RT it would be good if the wake-up in vfree_atomic() could be avoided in the scheduling path. Far worse are the other free_thread_stack() implementations which invoke __free_pages()/ kmem_cache_free() with disabled preemption. Cache the stack in free_thread_stack() in the VMAP_STACK case and RCU-delay the free path otherwise. Free the stack in the RCU callback. In the VMAP_STACK case this is another opportunity to fill the cache. Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Acked-by: Andy Lutomirski <luto@kernel.org> Link: https://lore.kernel.org/r/20220217102406.3697941-8-bigeasy@linutronix.de
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.