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Commit851a723e45("sched: Always clear user_cpus_ptr in do_set_cpus_allowed()") may call kfree() if user_cpus_ptr was previously set. Unfortunately, some of the callers of do_set_cpus_allowed() may have pi_lock held when calling it. So the following splats may be printed especially when running with a PREEMPT_RT kernel: WARNING: possible circular locking dependency detected BUG: sleeping function called from invalid context To avoid these problems, kfree_rcu() is used instead. An internal cpumask_rcuhead union is created for the sole purpose of facilitating the use of kfree_rcu() to free the cpumask. Since user_cpus_ptr is not being used in non-SMP configs, the newly introduced alloc_user_cpus_ptr() helper will return NULL in this case and sched_setaffinity() is modified to handle this special case. Fixes:851a723e45("sched: Always clear user_cpus_ptr in do_set_cpus_allowed()") Suggested-by: Peter Zijlstra <peterz@infradead.org> Signed-off-by: Waiman Long <longman@redhat.com> Signed-off-by: Ingo Molnar <mingo@kernel.org> Reviewed-by: Peter Zijlstra <peterz@infradead.org> Link: https://lore.kernel.org/r/20221231041120.440785-3-longman@redhat.com
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.