2023-08-03 18:42:19

by Alexander Lobakin

Subject: [PATCH net-next v3 5/6] page_pool: add a lockdep check for recycling in hardirq

From: Jakub Kicinski <[email protected]>

Page pool use in hardirq is prohibited, add debug checks
to catch misuses. IIRC we previously discussed using
DEBUG_NET_WARN_ON_ONCE() for this, but there were concerns
that people will have DEBUG_NET enabled in perf testing.
I don't think anyone enables lockdep in perf testing,
so use lockdep to avoid pushback and arguing :)

Signed-off-by: Jakub Kicinski <[email protected]>
Signed-off-by: Alexander Lobakin <[email protected]>
---
include/linux/lockdep.h | 7 +++++++
net/core/page_pool.c | 2 ++
2 files changed, 9 insertions(+)

diff --git a/include/linux/lockdep.h b/include/linux/lockdep.h
index 310f85903c91..dc2844b071c2 100644
--- a/include/linux/lockdep.h
+++ b/include/linux/lockdep.h
@@ -625,6 +625,12 @@ do { \
WARN_ON_ONCE(__lockdep_enabled && !this_cpu_read(hardirq_context)); \
} while (0)

+#define lockdep_assert_no_hardirq() \
+do { \
+ WARN_ON_ONCE(__lockdep_enabled && (this_cpu_read(hardirq_context) || \
+ !this_cpu_read(hardirqs_enabled))); \
+} while (0)
+
#define lockdep_assert_preemption_enabled() \
do { \
WARN_ON_ONCE(IS_ENABLED(CONFIG_PREEMPT_COUNT) && \
@@ -659,6 +665,7 @@ do { \
# define lockdep_assert_irqs_enabled() do { } while (0)
# define lockdep_assert_irqs_disabled() do { } while (0)
# define lockdep_assert_in_irq() do { } while (0)
+# define lockdep_assert_no_hardirq() do { } while (0)

# define lockdep_assert_preemption_enabled() do { } while (0)
# define lockdep_assert_preemption_disabled() do { } while (0)
diff --git a/net/core/page_pool.c b/net/core/page_pool.c
index 03ad74d25959..77cb75e63aca 100644
--- a/net/core/page_pool.c
+++ b/net/core/page_pool.c
@@ -587,6 +587,8 @@ static __always_inline struct page *
__page_pool_put_page(struct page_pool *pool, struct page *page,
unsigned int dma_sync_size, bool allow_direct)
{
+ lockdep_assert_no_hardirq();
+
/* This allocator is optimized for the XDP mode that uses
* one-frame-per-page, but have fallbacks that act like the
* regular page allocator APIs.
--
2.41.0

2023-08-04 10:45:46

by Jesper Dangaard Brouer

Subject: Re: [PATCH net-next v3 5/6] page_pool: add a lockdep check for recycling in hardirq

On 03/08/2023 20.20, Alexander Lobakin wrote:
> From: Jakub Kicinski<[email protected]>
>
> Page pool use in hardirq is prohibited, add debug checks
> to catch misuses. IIRC we previously discussed using
> DEBUG_NET_WARN_ON_ONCE() for this, but there were concerns
> that people will have DEBUG_NET enabled in perf testing.
> I don't think anyone enables lockdep in perf testing,
> so use lockdep to avoid pushback and arguing :)
>
> Signed-off-by: Jakub Kicinski<[email protected]>
> Signed-off-by: Alexander Lobakin<[email protected]>

I like this.

Acked-by: Jesper Dangaard Brouer <[email protected]>