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authorSebastian Siewior <bigeasy@linutronix.de>2016-03-08 10:03:56 +0100
committerMichael Ellerman <mpe@ellerman.id.au>2016-03-29 12:08:07 +1100
commit08a5bb2921e490939f78f38fd0d02858bb709942 (patch)
tree69ffd3a4d483b216da03d54daca1cfc5a28b7615 /arch
parentf55532a0c0b8bb6148f4e07853b876ef73bc69ca (diff)
powerpc/mm: Fixup preempt underflow with huge pages
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 <benh@kernel.crashing.org> Cc: Christoph Lameter <cl@linux.com> Cc: stable@vger.kernel.org Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> Reviewed-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Diffstat (limited to 'arch')
-rw-r--r--arch/powerpc/mm/hugetlbpage.c4
1 files changed, 2 insertions, 2 deletions
diff --git a/arch/powerpc/mm/hugetlbpage.c b/arch/powerpc/mm/hugetlbpage.c
index 6dd272b6196f..d991b9e80dbb 100644
--- a/arch/powerpc/mm/hugetlbpage.c
+++ b/arch/powerpc/mm/hugetlbpage.c
@@ -413,13 +413,13 @@ static void hugepd_free(struct mmu_gather *tlb, void *hugepte)
{
struct hugepd_freelist **batchp;
- batchp = this_cpu_ptr(&hugepd_freelist_cur);
+ batchp = &get_cpu_var(hugepd_freelist_cur);
if (atomic_read(&tlb->mm->mm_users) < 2 ||
cpumask_equal(mm_cpumask(tlb->mm),
cpumask_of(smp_processor_id()))) {
kmem_cache_free(hugepte_cache, hugepte);
- put_cpu_var(hugepd_freelist_cur);
+ put_cpu_var(hugepd_freelist_cur);
return;
}