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[bpf-next,v2,1/4] xsk: avoid store-tearing when assigning queues

Message ID 20190826061053.15996-2-bjorn.topel@gmail.com
State Changes Requested
Delegated to: BPF Maintainers
Headers show
Series xsk: various CPU barrier and {READ, WRITE}_ONCE fixes | expand

Commit Message

Björn Töpel Aug. 26, 2019, 6:10 a.m. UTC 
From: Björn Töpel <bjorn.topel@intel.com>

Use WRITE_ONCE when doing the store of tx, rx, fq, and cq, to avoid
potential store-tearing. These members are read outside of the control
mutex in the mmap implementation.

Acked-by: Jonathan Lemon <jonathan.lemon@gmail.com>
Fixes: 37b076933a8e ("xsk: add missing write- and data-dependency barrier")
Signed-off-by: Björn Töpel <bjorn.topel@intel.com>
---
 net/xdp/xsk.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
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Patch

diff --git a/net/xdp/xsk.c b/net/xdp/xsk.c
index ee4428a892fa..f3351013c2a5 100644
--- a/net/xdp/xsk.c
+++ b/net/xdp/xsk.c
@@ -409,7 +409,7 @@  static int xsk_init_queue(u32 entries, struct xsk_queue **queue,
 
 	/* Make sure queue is ready before it can be seen by others */
 	smp_wmb();
-	*queue = q;
+	WRITE_ONCE(*queue, q);
 	return 0;
 }