netdev - [PATCH net-next] bonding: make slave status notifications GFP

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Date:	Wed,  5 Mar 2014 14:15:53 +0100
From:	Veaceslav Falico <vfalico@...hat.com>
To:	netdev@...r.kernel.org
Cc:	Veaceslav Falico <vfalico@...hat.com>,
	Thomas Glanzmann <thomas@...nzmann.de>,
	Ding Tianhong <dingtianhong@...wei.com>,
	Jay Vosburgh <fubar@...ibm.com>,
	Andy Gospodarek <andy@...yhouse.net>
Subject: [PATCH net-next] bonding: make slave status notifications GFP_ATOMIC

Currently we're using GFP_KERNEL, however there are some path(s) where we
can hold some spinlocks, specifically bond->curr_slave_lock:

[    4.722916] BUG: sleeping function called from invalid context at mm/slub.c:965
[    4.724438] in_atomic(): 1, irqs_disabled(): 0, pid: 940, name: ifup-eth
[    4.726034] 5 locks held by ifup-eth/940:
...snip...
[    4.734646]  #4:  (&bond->curr_slave_lock){+...+.}, at: [<ffffffffa00badc6>] bond_enslave+0xda6/0xdd0 [bonding]
...snip...
[    4.759081]  [<ffffffffa00b6f11>] bond_change_active_slave+0x191/0x3b0 [bonding]
[    4.760917]  [<ffffffffa00b7227>] bond_select_active_slave+0xf7/0x1d0 [bonding]
[    4.762751]  [<ffffffffa00badce>] bond_enslave+0xdae/0xdd0 [bonding]
...snip...

As it's out of hot path and is a really rare event - change the gfp_t flags
to GFP_ATOMIC to avoid sleeping under spinlock.

CC: Thomas Glanzmann <thomas@...nzmann.de>
CC: Ding Tianhong <dingtianhong@...wei.com>
CC: Jay Vosburgh <fubar@...ibm.com>
CC: Andy Gospodarek <andy@...yhouse.net>
Signed-off-by: Veaceslav Falico <vfalico@...hat.com>
---
 drivers/net/bonding/bonding.h | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/net/bonding/bonding.h b/drivers/net/bonding/bonding.h
index 4303628..4cd451d 100644
--- a/drivers/net/bonding/bonding.h
+++ b/drivers/net/bonding/bonding.h
@@ -292,7 +292,7 @@ static inline void bond_set_active_slave(struct slave *slave)
 {
 	if (slave->backup) {
 		slave->backup = 0;
-		rtmsg_ifinfo(RTM_NEWLINK, slave->dev, 0, GFP_KERNEL);
+		rtmsg_ifinfo(RTM_NEWLINK, slave->dev, 0, GFP_ATOMIC);
 	}
 }
 
@@ -300,7 +300,7 @@ static inline void bond_set_backup_slave(struct slave *slave)
 {
 	if (!slave->backup) {
 		slave->backup = 1;
-		rtmsg_ifinfo(RTM_NEWLINK, slave->dev, 0, GFP_KERNEL);
+		rtmsg_ifinfo(RTM_NEWLINK, slave->dev, 0, GFP_ATOMIC);
 	}
 }
 
-- 
1.8.4

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