[PATCH 2/6] mm/kasan: don't reduce quarantine in atomic contexts

Andrey Ryabinin
2016-08-01T16:19:34Z

Currently we call quarantine_reduce() for ___GFP_KSWAPD_RECLAIM
(implied by __GFP_RECLAIM) allocation. So, basically we call it on
almost every allocation. quarantine_reduce() sometimes is heavy operation,
and calling it with disabled interrupts may trigger hard LOCKUP:

NMI watchdog: Watchdog detected hard LOCKUP on cpu 2irq event stamp: 1411258
Call Trace:
<NMI> [<ffffffff98a48532>] dump_stack+0x68/0x96
[<ffffffff98357fbb>] watchdog_overflow_callback+0x15b/0x190
[<ffffffff9842f7d1>] __perf_event_overflow+0x1b1/0x540
[<ffffffff98455b14>] perf_event_overflow+0x14/0x20
[<ffffffff9801976a>] intel_pmu_handle_irq+0x36a/0xad0
[<ffffffff9800ba4c>] perf_event_nmi_handler+0x2c/0x50
[<ffffffff98057058>] nmi_handle+0x128/0x480
[<ffffffff980576d2>] default_do_nmi+0xb2/0x210
[<ffffffff980579da>] do_nmi+0x1aa/0x220
[<ffffffff99a0bb07>] end_repeat_nmi+0x1a/0x1e
<<EOE>> [<ffffffff981871e6>] __kernel_text_address+0x86/0xb0
[<ffffffff98055c4b>] print_context_stack+0x7b/0x100
[<ffffffff98054e9b>] dump_trace+0x12b/0x350
[<ffffffff98076ceb>] save_stack_trace+0x2b/0x50
[<ffffffff98573003>] set_track+0x83/0x140
[<ffffffff98575f4a>] free_debug_processing+0x1aa/0x420
[<ffffffff98578506>] __slab_free+0x1d6/0x2e0
[<ffffffff9857a9b6>] ___cache_free+0xb6/0xd0
[<ffffffff9857db53>] qlist_free_all+0x83/0x100
[<ffffffff9857df07>] quarantine_reduce+0x177/0x1b0
[<ffffffff9857c423>] kasan_kmalloc+0xf3/0x100

Reduce the quarantine_reduce iff direct reclaim is allowed.

Fixes: 55834c59098d("mm: kasan: initial memory quarantine implementation")
Reported-by: Dave Jones <davej@codemonkey.org.uk>
Signed-off-by: Andrey Ryabinin <aryabinin@virtuozzo.com>
---
mm/kasan/kasan.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/mm/kasan/kasan.c b/mm/kasan/kasan.c
index 3019cec..c99ef40 100644
--- a/mm/kasan/kasan.c
+++ b/mm/kasan/kasan.c
@@ -565,7 +565,7 @@ void kasan_kmalloc(struct kmem_cache *cache, const void *object, size_t size,
unsigned long redzone_start;
unsigned long redzone_end;

- if (flags & __GFP_RECLAIM)
+ if (gfpflags_allow_blocking(flags))
quarantine_reduce();

if (unlikely(object == NULL))
@@ -596,7 +596,7 @@ void kasan_kmalloc_large(const void *ptr, size_t size, gfp_t flags)
unsigned long redzone_start;
unsigned long redzone_end;

- if (flags & __GFP_RECLAIM)
+ if (gfpflags_allow_blocking(flags))
quarantine_reduce();

if (unlikely(ptr == NULL))
--
2.7.3