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This is similar to NTSYNC_IOC_WAIT_ANY, but waits until all of the objects are simultaneously signaled, and then acquires all of them as a single atomic operation. Because acquisition of multiple objects is atomic, some complex locking is required. We cannot simply spin-lock multiple objects simultaneously, as that may disable preëmption for a problematically long time. Instead, modifying any object which may be involved in a wait-all operation takes a device-wide sleeping mutex, "wait_all_lock", instead of the normal object spinlock. Because wait-for-all is a rare operation, in order to optimize wait-for-any, this lock is only taken when necessary. "all_hint" is used to mark objects which are involved in a wait-for-all operation, and if an object is not, only its spinlock is taken. The locking scheme used here was written by Peter Zijlstra. Signed-off-by: Elizabeth Figura <zfigura@codeweavers.com> Link: https://lore.kernel.org/r/20241213193511.457338-5-zfigura@codeweavers.com Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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 reStructuredText 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.