cf4466ea47
KCSAN detected an data race with ipc/sem.c that is intentional. As nf_conntrack_lock() uses the same algorithm: Update nf_conntrack_core as well: nf_conntrack_lock() contains a1) spin_lock() a2) smp_load_acquire(nf_conntrack_locks_all). a1) actually accesses one lock from an array of locks. nf_conntrack_locks_all() contains b1) nf_conntrack_locks_all=true (normal write) b2) spin_lock() b3) spin_unlock() b2 and b3 are done for every lock. This guarantees that nf_conntrack_locks_all() prevents any concurrent nf_conntrack_lock() owners: If a thread past a1), then b2) will block until that thread releases the lock. If the threat is before a1, then b3)+a1) ensure the write b1) is visible, thus a2) is guaranteed to see the updated value. But: This is only the latest time when b1) becomes visible. It may also happen that b1) is visible an undefined amount of time before the b3). And thus KCSAN will notice a data race. In addition, the compiler might be too clever. Solution: Use WRITE_ONCE(). Signed-off-by: Manfred Spraul <manfred@colorfullife.com> Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.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 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.