Sebastian Andrzej Siewior <bige...@linutronix.de> writes:
> [ text/plain ]
> 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 94b09d755462 ("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 69111bac42f5 ("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 <b...@kernel.crashing.org>
> Cc: Christoph Lameter <c...@linux.com>
> Cc: Michael Ellerman <m...@ellerman.id.au>
> Cc: Tiejun Chen <tiejun.c...@windriver.com>
> Cc: <sta...@vger.kernel.org>
> Signed-off-by: Sebastian Andrzej Siewior <bige...@linutronix.de>
> ---
> arch/powerpc/mm/hugetlbpage.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/arch/powerpc/mm/hugetlbpage.c b/arch/powerpc/mm/hugetlbpage.c
> index 744e24bcb85c..9e8919b39640 100644
> --- a/arch/powerpc/mm/hugetlbpage.c
> +++ b/arch/powerpc/mm/hugetlbpage.c
> @@ -414,7 +414,7 @@ static void hugepd_free(struct mmu_gather *tlb, void
> *hugepte)
> {
> struct hugepd_freelist **batchp;
>
> - batchp = this_cpu_ptr(&hugepd_freelist_cur);
> + batchp = get_cpu_ptr(&hugepd_freelist_cur);
>
> if (atomic_read(&tlb->mm->mm_users) < 2 ||
> cpumask_equal(mm_cpumask(tlb->mm),
IMHO it would better if we do
batchp = get_cpu_var(hugepd_freelist_cpu);
so that it match the existing
put_cpu_var(hugepd_freelist_cur);
While you are there, can you also fix the wrong indentation on line 423
?
-aneesh
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