summaryrefslogtreecommitdiffstats
path: root/arch/powerpc/perf/callchain.c
diff options
context:
space:
mode:
authorAneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>2015-10-09 05:02:21 +0200
committerMichael Ellerman <mpe@ellerman.id.au>2015-10-12 06:30:09 +0200
commit891121e6c02c6242487aa4ea1d5c75b7ecdc45ee (patch)
tree118c5b4df68fe004438e4a1a629b04fbeed9b417 /arch/powerpc/perf/callchain.c
parentpowerpc/mm: Disable hugepd for 64K page size. (diff)
downloadlinux-891121e6c02c6242487aa4ea1d5c75b7ecdc45ee.tar.xz
linux-891121e6c02c6242487aa4ea1d5c75b7ecdc45ee.zip
powerpc/mm: Differentiate between hugetlb and THP during page walk
We need to properly identify whether a hugepage is an explicit or a transparent hugepage in follow_huge_addr(). We used to depend on hugepage shift argument to do that. But in some case that can result in wrong results. For ex: On finding a transparent hugepage we set hugepage shift to PMD_SHIFT. But we can end up clearing the thp pte, via pmdp_huge_get_and_clear. We do prevent reusing the pfn page via the usage of kick_all_cpus_sync(). But that happens after we updated the pte to 0. Hence in follow_huge_addr() we can find hugepage shift set, but transparent huge page check fail for a thp pte. NOTE: We fixed a variant of this race against thp split in commit 691e95fd7396905a38d98919e9c150dbc3ea21a3 ("powerpc/mm/thp: Make page table walk safe against thp split/collapse") Without this patch, we may hit the BUG_ON(flags & FOLL_GET) in follow_page_mask occasionally. In the long term, we may want to switch ppc64 64k page size config to enable CONFIG_ARCH_WANT_GENERAL_HUGETLB Reported-by: David Gibson <david@gibson.dropbear.id.au> Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Diffstat (limited to 'arch/powerpc/perf/callchain.c')
-rw-r--r--arch/powerpc/perf/callchain.c2
1 files changed, 1 insertions, 1 deletions
diff --git a/arch/powerpc/perf/callchain.c b/arch/powerpc/perf/callchain.c
index ff09cde20cd2..e04a6752b399 100644
--- a/arch/powerpc/perf/callchain.c
+++ b/arch/powerpc/perf/callchain.c
@@ -127,7 +127,7 @@ static int read_user_stack_slow(void __user *ptr, void *buf, int nb)
return -EFAULT;
local_irq_save(flags);
- ptep = find_linux_pte_or_hugepte(pgdir, addr, &shift);
+ ptep = find_linux_pte_or_hugepte(pgdir, addr, NULL, &shift);
if (!ptep)
goto err_out;
if (!shift)