[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Date: Thu, 9 Oct 2014 22:24:51 -0700
From: Eric Dumazet <edumazet@...gle.com>
To: "David S. Miller" <davem@...emloft.net>
Cc: netdev@...r.kernel.org,
Alexander Duyck <alexander.h.duyck@...hat.com>,
Andres Lagar-Cavilla <andreslc@...gle.com>,
Greg Thelen <gthelen@...gle.com>,
Hugh Dickins <hughd@...gle.com>,
David Rientjes <rientjes@...gle.com>,
Eric Dumazet <edumazet@...gle.com>
Subject: [PATCH net 2/5] igb: fix race accessing page->_count
This is illegal to use atomic_set(&page->_count, 2) even if we 'own'
the page. Other entities in the kernel need to use get_page_unless_zero()
to get a reference to the page before testing page properties, so we could
loose a refcount increment.
Signed-off-by: Eric Dumazet <edumazet@...gle.com>
---
drivers/net/ethernet/intel/igb/igb_main.c | 7 +++----
1 file changed, 3 insertions(+), 4 deletions(-)
diff --git a/drivers/net/ethernet/intel/igb/igb_main.c b/drivers/net/ethernet/intel/igb/igb_main.c
index ae59c0b108c5..a21b14495ebd 100644
--- a/drivers/net/ethernet/intel/igb/igb_main.c
+++ b/drivers/net/ethernet/intel/igb/igb_main.c
@@ -6545,11 +6545,10 @@ static bool igb_can_reuse_rx_page(struct igb_rx_buffer *rx_buffer,
/* flip page offset to other buffer */
rx_buffer->page_offset ^= IGB_RX_BUFSZ;
- /* since we are the only owner of the page and we need to
- * increment it, just set the value to 2 in order to avoid
- * an unnecessary locked operation
+ /* Even if we own the page, we are not allowed to use atomic_set()
+ * This would break get_page_unless_zero() users.
*/
- atomic_set(&page->_count, 2);
+ atomic_inc(&page->_count);
#else
/* move offset up to the next cache line */
rx_buffer->page_offset += truesize;
--
2.1.0.rc2.206.gedb03e5
--
To unsubscribe from this list: send the line "unsubscribe netdev" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Powered by blists - more mailing lists