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tasklet_unlock_wait() spin waits for TASKLET_STATE_RUN to be cleared. This is wasting CPU cycles in a tight loop which is especially painful in a guest when the CPU running the tasklet is scheduled out. tasklet_unlock_wait() is invoked from tasklet_kill() which is used in teardown paths and not performance critical at all. Replace the spin wait with wait_var_event(). There are no users of tasklet_unlock_wait() which are invoked from atomic contexts. The usage in tasklet_disable() has been replaced temporarily with the spin waiting variant until the atomic users are fixed up and will be converted to the sleep wait variant later. Signed-off-by: Peter Zijlstra <peterz@infradead.org> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org> Link: https://lore.kernel.org/r/20210309084241.783936921@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.