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commit93ee385254upstream. The code for syncing vmalloc memory PGD pointers is using atomic_read() in pair with atomic_set_release() but the proper pairing is atomic_read_acquire() paired with atomic_set_release(). This is done to clearly instruct the compiler to not reorder the memcpy() or similar calls inside the section so that we do not observe changes to init_mm. memcpy() calls should be identified by the compiler as having unpredictable side effects, but let's try to be on the safe side. Cc: stable@vger.kernel.org Fixes:d31e23aff0("ARM: mm: make vmalloc_seq handling SMP safe") Suggested-by: Mark Rutland <mark.rutland@arm.com> Signed-off-by: Linus Walleij <linus.walleij@linaro.org> Signed-off-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>