• S
    powerpc/mm: Fixup preempt underflow with huge pages · 08a5bb29
    Sebastian Siewior 提交于
    hugepd_free() used __get_cpu_var() once. Nothing ensured that the code
    accessing the variable did not migrate from one CPU to another and soon
    this was noticed by Tiejun Chen in 94b09d75 ("powerpc/hugetlb:
    Replace __get_cpu_var with get_cpu_var"). So we had it fixed.
    
    Christoph Lameter was doing his __get_cpu_var() replaces and forgot
    PowerPC. Then he noticed this and sent his fixed up batch again which
    got applied as 69111bac ("powerpc: Replace __get_cpu_var uses").
    
    The careful reader will noticed one little detail: get_cpu_var() got
    replaced with this_cpu_ptr(). So now we have a put_cpu_var() which does
    a preempt_enable() and nothing that does preempt_disable() so we
    underflow the preempt counter.
    
    Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
    Cc: Christoph Lameter <cl@linux.com>
    Cc: stable@vger.kernel.org
    Signed-off-by: NSebastian Andrzej Siewior <bigeasy@linutronix.de>
    Reviewed-by: NAneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
    Signed-off-by: NMichael Ellerman <mpe@ellerman.id.au>
    08a5bb29
hugetlbpage.c 25.2 KB