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Will Deacon
86c9e8126e
Jiankang reports that our race detection in set_pte_at is firing when copying the page tables in dup_mmap as a result of a fork(). In this situation, the page table isn't actually live and so there is no way that we can race with a concurrent update from the hardware page table walker. This patch reworks the race detection so that we require either the mm to match the current active_mm (i.e. currently installed in our TTBR0) or the mm_users count to be greater than 1, implying that the page table could be live in another CPU. The mm_users check might still be racy, but we'll avoid false positives and it's not realistic to validate that all the necessary locks are held as part of this assertion. Cc: Yisheng Xie <xieyisheng1@huawei.com> Reported-by: Jiankang Chen <chenjiankang1@huawei.com> Tested-by: Jiankang Chen <chenjiankang1@huawei.com> Signed-off-by: Will Deacon <will.deacon@arm.com>
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.