diff mbox series

[net-next,2/7] net: Don't disable interrupts in __netdev_alloc_skb()

Message ID 20190529221523.22399-3-bigeasy@linutronix.de
State Changes Requested
Delegated to: David Miller
Headers show
Series Avoid local_irq_save() and use napi_alloc_frag() where possible | expand

Commit Message

Sebastian Andrzej Siewior May 29, 2019, 10:15 p.m. UTC
__netdev_alloc_skb() can be used from any context and is used by NAPI
and non-NAPI drivers. Non-NAPI drivers use it in interrupt context and
NAPI drivers use it during initial allocation (->ndo_open() or
->ndo_change_mtu()). Some NAPI drivers share the same function for the
initial allocation and the allocation in their NAPI callback.

The interrupts are disabled in order to ensure locked access from every
context to `netdev_alloc_cache'.

Let __netdev_alloc_skb() check if interrupts are disabled. If they are, use
`netdev_alloc_cache'. Otherwise disable BH and use `napi_alloc_cache.page'.
The IRQ check is cheaper compared to disabling & enabling interrupts and
memory allocation with disabled interrupts does not work on -RT.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
---
 net/core/skbuff.c | 19 +++++++++++--------
 1 file changed, 11 insertions(+), 8 deletions(-)
diff mbox series

Patch

diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index 8a5ff67e14d90..7f714a1196b90 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -426,7 +426,6 @@  struct sk_buff *__netdev_alloc_skb(struct net_device *dev, unsigned int len,
 				   gfp_t gfp_mask)
 {
 	struct page_frag_cache *nc;
-	unsigned long flags;
 	struct sk_buff *skb;
 	bool pfmemalloc;
 	void *data;
@@ -447,13 +446,17 @@  struct sk_buff *__netdev_alloc_skb(struct net_device *dev, unsigned int len,
 	if (sk_memalloc_socks())
 		gfp_mask |= __GFP_MEMALLOC;
 
-	local_irq_save(flags);
-
-	nc = this_cpu_ptr(&netdev_alloc_cache);
-	data = page_frag_alloc(nc, len, gfp_mask);
-	pfmemalloc = nc->pfmemalloc;
-
-	local_irq_restore(flags);
+	if (irqs_disabled()) {
+		nc = this_cpu_ptr(&netdev_alloc_cache);
+		data = page_frag_alloc(nc, len, gfp_mask);
+		pfmemalloc = nc->pfmemalloc;
+	} else {
+		local_bh_disable();
+		nc = this_cpu_ptr(&napi_alloc_cache.page);
+		data = page_frag_alloc(nc, len, gfp_mask);
+		pfmemalloc = nc->pfmemalloc;
+		local_bh_enable();
+	}
 
 	if (unlikely(!data))
 		return NULL;