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If a writer could been woken up, the above branch if (sem->count == 0) break; would have moved us to taking the sem. So, it's not the time to wake a writer now, and only readers are allowed now. Thus, 0 must be passed to __rwsem_do_wake(). Next, __rwsem_do_wake() wakes readers unconditionally. But we mustn't do that if the sem is owned by writer in the moment. Otherwise, writer and reader own the sem the same time, which leads to memory corruption in callers. rwsem-xadd.c does not need that, as: 1) the similar check is made lockless there, 2) in __rwsem_mark_wake::try_reader_grant we test, that sem is not owned by writer. Signed-off-by: Kirill Tkhai <ktkhai@virtuozzo.com> Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: <stable@vger.kernel.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Niklas Cassel <niklas.cassel@axis.com> Cc: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Fixes: 17fcbd590d0c "locking/rwsem: Fix down_write_killable() for CONFIG_RWSEM_GENERIC_SPINLOCK=y" Link: http://lkml.kernel.org/r/149762063282.19811.9129615532201147826.stgit@localhost.localdomain Signed-off-by: Ingo Molnar <mingo@kernel.org>
Linux kernel ============ This file was moved to Documentation/admin-guide/README.rst Please notice that there are several guides for kernel developers and users. These guides can be rendered in a number of formats, like HTML and PDF. In order to build the documentation, use ``make htmldocs`` or ``make pdfdocs``. There are various text files in the Documentation/ subdirectory, several of them using the Restructured Text markup notation. See Documentation/00-INDEX for a list of what is contained in each file. 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.