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rcuref_read() returns the number of references that are currently held. If 0 is returned then it is not safe to assume that the object ca be scheduled for deconstruction because it is marked DEAD. This happens if the return value of rcuref_put() is ignored and assumptions are made. If 0 is returned then the counter transitioned from 0 to RCUREF_NOREF. If rcuref_put() did not return to the caller then the counter did not yet transition from RCUREF_NOREF to RCUREF_DEAD. This means that there is still a chance that the counter will transition from RCUREF_NOREF to 0 meaning it is still valid and must not be deconstructed. In this brief window rcuref_read() will return 0. Provide rcuref_is_dead() to determine if the counter is marked as RCUREF_DEAD. Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Link: https://lore.kernel.org/r/20250416162921.513656-2-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 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.